CHEMISTRY OLYMPAID 99:

1. Which oxide forms a basic solution when mixed with water?

(A) K2O

(B) Al2O3

(C) CO2

(D) SO3

2. Which of these compounds is not white?

1. KMnO4

2. ZnSO4

3. FeCl3

(A) 1 only

(B) 1 and 3 only

(C) 2 and 3 only

(D) 1, 2, and 3

3. Which gas will cause a solution containing potassium iodide and starch

to turn a blue-black color?

(A) H2

(B) CO2

(C) Cl2

(D) NH3

4. A colorless aqueous solution contains a single ionic compound. Use this

experimental information to deduce the identity of the compound.

* When a small amount of dilute NaOH solution is added to the solution,

a precipitate forms. This precipitate dissolves when excess NaOH is added.

* Addition of AgC2H3O2 to the solution gives a white precipitate.

(A) AlCl3

(B) Ba(NO3)2

(C) CuSO4

(D) FeI2

5. The most active metals on the periodic table have

(A) large radii and high electronegativities.

(B) small radii and low electronegativities.

(C) small radii and low ionization energies.

(D) large radii and low ionization energies.

6. The aqueous solubilities of several compounds between temperatures of 0

°C and 80 °C are shown in this diagram. Which compound can be recovered

with the highest percent yield by dissolving a sample in water at 80 °C and

cooling to 0 °C?

(A) A

(B) B

(C) C

(D) D

7. A student determines the concentration of a solution of NaOH. She pipets

a sample of the NaOH solution into a flask and adds two drops of an

indicator. Standardized acid is added from a buret until the indicator

changes color. Which device may contain residual water without affecting

the results of the titration?

1. buret

2. flask

3. pipet

(A) 1 only

(B) 2 only

(C) 1 and 3 only

(D) 2 and 3 only

8. The density of a block of metal is determined by weighing it, then

submerging it in water. Based on these data, to how many significant

figures should the density be reported?

Data

mass of block 25.472 g

volume of H2O 10.5 mL

volume of H2O

with block 20.0 mL

(A) 2

(B) 3

(C) 4

(D) 5

9. Arsenic(III) sulfide reacts with oxygen to form arsenic(III) oxide and

sulfur(IV) oxide as represented by this equation.

__As2S3 + __O2 ---> __As2O3 + __SO2

What is the coefficient for O2 when this equation is balanced using whole

number coefficients?

(A) 5

(B) 7

(C) 9

(D) 11

10. How many grams of MgCO3 contain 24.0 g of oxygen? (The molar mass of

MgCO3 is 84.3 g mol¯1)

(A) 42.2 g

(B) 84.3 g

(C) 126 g

(D) 154 g

11. How many hydrogen atoms are present in one mole of ammonium benzoate,

NH4C7H5O2?

(A) 6.0 x 1023

(B) 2.4 x 1024

(C) 3.0 x 1024

(D) 5.4 x 1024

12. Consider this balanced equation:

3 H2(g) + CO(g) ---> CH4(g) + H2O(g)

How many moles of CH4 can be obtained by reacting 2.0 mol of H2 with 2.0

mol CO according to this equation?

(A) 0.33 mol

(B) 0.67 mol

(C) 2.0 mol

(D) 3.0 mol

13. What is the molarity of the chloride ion in 250 mL of a solution

containing 1.90 g of MgCl2? (The molar mass of MgCl2 is 95.2 g mol¯1

(A) 0.020 M

(B) 0.040 M

(C) 0.080 M

(D) 0.16 M

14. Consider this equation.

2 SO2(g) + O2(g) --> 2 SO3(g)

What happens to the total volume when 3.0 L of SO2 and 2.0 L of O2 react to

form the maximum amount of SO3 possible from these volumes of reactants.

Assume all gases are at the same constant temperature and pressure.

(A) It decreases by 1.5 L.

(B) It decreases by 1.0 L.

(C) It increases by 0.50 L.

(D) It remains constant.

15. What is the molarity of an H2SO4 solution if 25.00 mL is exactly

neutralized by 32.63 mL of 0.164 M NaOH?

(A) 0.107 M

(B) 0.126 M

(C) 0.214 M

(D) 0.428 M

16. Which element exists as a solid at 25 °C and one atmosphere of

pressure?

(A) bromine

(B) chlorine

(C) mercury

(D) phosphorus

17. "Dry ice" is solid carbon dioxide. To which class of solids does it

belong?

(A) amorphous solid

(B) molecular solid

(C) network solid

(D) polymeric solid

18. Which of these factors affect the average kinetic energy of the

molecules in a gas?

1. pressure

2. temperature

(A) 1 only

(B) 2 only

(C) both 1 and 2

(D) neither 1 nor 2

19. How does the vapor pressure of a liquid in a stoppered flask change if

the quantity of liquid is doubled?

(A) It doubles

(B) It increases slightly

(C) It decreases.

(D) It does not change.

20. What type of forces must be overcome when liquid ammonia vaporizes?

1. covalent bonds

2. dispersion forces

3. hydrogen bonds

(A) 1 only

(B) 2 only

(C) 2 and 3 only

(D) 1, 2, and 3

21. The temperature of a gas sample is increased from 50 °C to 100 °C. By

what factor must the pressure be changed if the volume is to be kept

constant?

(A) 0.5

(B) 0.87

(C) 1.15

(D) 2.0

22. What is the molar mass of a gas that diffuses twice as fast as SO2?

(The molar mass of SO2 is 64 g mol¯1)

(A) 16 g mol¯1

(B) 32 g mol¯1

(C) 128 g mol¯1

(D) 256 g mol¯1

23. How many grams of ice at 0 °C can be melted by the addition of 500 J of

heat? (The molar heat of fusion for ice is 6.02 kJ mol¯1)

(A) 0.0831 g

(B) 1.50 g

(C) 3.01 g

(D) 12.0 g

3 O2(g) --> 2 O3(g)

24. This reaction is endothermic. What can be concluded about the average

energy per bond in O2 and O3?

(A) The average energy per bond in O2 is greater than the average

energy per bond in O3.

(B) The average energy per bond in O2 is less than the average energy

per bond in O3.

(C) The average energy per bond in O2 is the same as the average energy

per bond in O3.

(D) No conclusion can be drawn about the average bond energies from

this information alone.

25. Under which set of conditions is a chemical reaction most likely to be

spontaneous?

DH DS T (temperature)

(A) - - low

(B) - - high

(C) + + low

(D) + - high

26. For which reaction do you expect DS to be negative?

(A) 2C(s) + O2(g) --> 2CO(g)

(B) Br2(s) --> Br2(l)

(C) H2O(l, 25 °C) --> H2O(l, 50 °C)

(D) Cl2(g) + 2HI(g) --> I2(s) + HCl(g)

Reaction Enthalpy

Change, DH

Mg(s) + 2 HCl(aq) --> MgCl2(aq) + H2(g) -467 kJ mol¯1

MgO(s) + 2 HCl(aq) --> MgCl2(aq) + H2O(l) -151 kJ mol¯1

27. According to this information, and given the fact that for water, DH =

-286 kJ mol¯1, what is DH for MgO(s)?

(A) -904 kJ mol¯1

(B) -602 kJ mol¯1

(C) -334 k J mol¯1

(D) -30 kJ mol¯1

28. The rate of a reaction with just two reactants is observed to double

when the concentration of one reactant is doubled and the second reactant

is held constant. The rate is also observed to increase by a factor of nine

when the concentration of the second reactant is tripled, holding the

concentration of the first reactant constant. What is the overall order for

this reaction?

(A) 2

(B) 3

(C) 5

(D) 6

29. Which energy diagram represents a highly exothermic reaction that has a

small activation energy? (Assume that all curves are plotted on the same

scale.)

30. Tritium decays by a first-order process that has half-life of 12.5

years. How many years will it take to reduce the radioactivity of a tritium

sample to 15% of it original value?

(A) 64 y

(B) 54 y

(C) 34 y

(D) 24 y

31. What is the overall order of a reaction with a rate constant having the

units L mol¯1 s¯1?

(A) 0

(B) 1

(C) 2

(D) 3

32. In a reaction with several steps, which step limits the rate of the

reaction?

(A) first

(B) last

(C) fastest

(D) slowest

P4(s) + 5 O2(g) <===> P4O10(s)

33. What is the equilibrium expression for this reaction?

(A) Kc = [P4O10] / [P4] [O2]5

(B) Kc = [P4O10] / 5 [P4] [O2]

(C) Kc = [O2]5

(D) Kc = 1 / [O2}5

Fe3O4(s) + 4 H2(g) <===> 3 Fe(s) + 4 H2O(g)

DH > 0

34. For this reaction at equilibrium, which changes will increase the

quantity of Fe(s)?

1. increasing temperature

2. decreasing temperature

3. adding Fe3O4(s)

(A) 1 only

(B) 1 and 2 only

(C) 2 and 3 only

(D) 1,2, and 3

35. Which 0.1 M solution has the highest pH?

(A) sodium carbonate

(B) sodium chloride

(C) ammonium carbonate

(D) ammonium chloride

36. Which is the strongest acid?

(A) acetic acid - (Ka = 1.8 x 10¯5)

(B) benzoic acid - (Ka = 6.3 x 10¯5)

(C) formic acid - (Ka = 1.8 x 10¯4)

(D) nitrous acid - (Ka = 6.0 x 10¯4)

37. What is the order of concentration of the ions and molecules in a

nitrous acid solution? Nitrous acid, HNO2, is a weak acid.

(A) H3O+ = NO2¯ > HNO2 > OH¯

(B) H3O+ = NO2¯ = HNO2 = OH¯

(C) HNO2 > H3O+ = NO2¯ > OH¯

(D) HNO2 > NO2¯ > H3O+ > OH¯

38. Which acid, together with its sodium salt, would be best for preparing

a buffer with a pH = 4.5?

(A) HCN - (Ka = 4.9 x 10¯10)

(B) C3H5O2H - (Ka = 1.3 x 10¯5)

(C) HF - (Ka = 6.8 x 10¯4)

(D) ClC2H2O2H - (Ka = 1.4 x 10¯3)

39. What is the pH of a solution that contains 0.50 M sodium benzoate and

0.75 M benzoic acid? (Ka= 6.8 x 10¯5)

(A) 3.99

(B) 4.34

(C) 4.57

(D) 5.22

40. The solubility of lead(II) carbonate is 2.7 x 10¯7 mol L¯1. What is its

Ksp?

(A) 5.2 x 10¯4

(B) 2.7 x 10¯7

(C) 7.3 x 10¯14

(D) 3.9 x 10¯20

S4O62¯ + 10 H2O --> 4 SO42¯ + 20 H+ + 14 e¯

41. What is the change in oxidation number of sulfur in the half-reaction?

(A) -2 to -8

(B) +4 to +1

(C) +4 to +6

(D) +2 1/2 to +6

HAsO2(aq) + Sn2+(aq) + H+(aq) --> As(s) + An4+(aq) + H2O(l)

42. What is the oxidizing agent in the unbalanced equation?

(A) HAsO2(aq)

(B) Sn2+(aq)

(C) H+(aq)

(D) Sn4+(aq)

Fe3+(aq) + e¯ ---> Fe2+(aq) E = +0.77 V

Sn2+(aq) + 2e¯ ---> Sn(s) E = -0.14 V

43. According to the E values, what is the potential for this reaction

under standard conditions?

Sn(s) + 2 Fe3+(aq) ---> 2 Fe2+(aq) + Sn2+(aq)

(A) 1.68 V

(B) 1.40 V

(C) 0.91 V

(D) 0.63 V

44. When a sample of molten sodium chloride is electrolyzed for a given

length of time, how do the number of moles of sodium metal and chlorine gas

produced compare?

(A) The moles of sodium metal are equal to the moles of chlorine gas.

(B) There are twice as many moles of sodium metal as as moles of

chlorine gas

(C) There are three times as many moles of sodium metal as moles of

chlorine gas.

(D) There are four times as many moles of sodium metal as moles of

chlorine gas.

45. Which element has a partially-filled f subshell?

(A) Ba

(B) Eu

(C) Re

(D) Bi

46. How many orbitals have the quantum numbers n = 4 and l = 2?

(A) 1

(B) 3

(C) 5

(D) 7

47. Which element has the highest second ionization energy?

(A) Be

(B) Li

(C) B

(D) C

48. Which ion in the gaseous state has the greatest number of unpaired

electrons?

(A) Ni2+

(B) Cu2+

(C) Zn2+

(D) Ge2+

49. Which property decreases crossing the periodic table from left to right

and increases from top to bottom?

(A) ionization energy

(B) electron affinity

(C) electronegativity

(D) atomic radius

50. Which compound contains both covalent and ionic bonds?

(A) calcium oxide, CaO

(B) methyl fluoride, CH3F

(C) sodium peroxide, Na2O2

(D) hypochlorous acid, HOCl

51. Which species has a Lewis structure most like that of CO32¯?

(A) NO3¯

(B) BCl3

(C) NCl3

(D) SO32¯

52. Which element has the greatest electronegativity?

(A) As

(B) Ge

(C) P

(D) Sb

53. Which element has the highest melting point?

(A) Al

(B) Si

(C) P

(D) S

54. For which pair of species is the hybridization of the central atom the

same?

(A) NH3, NH4+

(B) NO2+ , NO2¯

(C) PF3, PF5

(D) BF3, BF4¯

55. Arrange the species in order of decreasing H-N-H bond angle.

(A) NH2¯ > NH3 > NH4+

(B) NH3 > NH4+ > NH2¯

(C) NH3 > NH2¯ > NH4+

(D) NH4+ > NH3 > NH2¯

56. How many moles of water would be produced by the complete combustion of

one mole of benzene, C6H6, in excess oxygen?

(A) 2

(B) 3

(C) 4

(D) 6

57. Ketene has the formula H2C=C=O. How many sigma and pi bonds does it

have?

sigma bonds pi bonds

(A) 6 2

(B) 6 0

(C) 4 2

(D) 2 2

58. The prefixes used to designate organic compounds with 3 and 4 carbon

atoms are, respectively,

(A) tri- and tetra-

(B) tri- and quatr-

(C) ter- and prop-

(D) prop- and but-

59. Which functional group is characteristic of proteins?

60. Which substance is most likely to be used as a soap?

(A) CH3(CH2)12CO2CH3

(B) CH3(CH2)5O(CH2)5CH3

(C) CH3(CH2)12CO2Na

(D) CH3(CH2)12CHCl2

Answers:

# Ans. # Ans. # Ans.

1. A 21. C 41. D

2. B 22. A 42. A

3. C 23. B 43. C

4. A 24. A 44. B

5. D 25. A 45. B

6. C 26. D 46. C

7. B 27. B 47. B

8. A 28. B 48. A

9. C 29. D 49. D

10. A 30. C 50. C

11. D 31. C 51. A

12. B 32. D 52. C

13. D 33. D 53. B

14. A 34. A 54. A

15. A 35. A 55. D

16. D 36. D 56. B

17. B 37. C 57. C

18. B 38. B 58. D

19. D 39. A 59. D

20. C 40. C 60. C

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chemistry olympaid 1998:local test

1. Which gas is most soluble in water?

(A) ammonia

(B) hydrogen

(C) methane

(D) nitrogen

2. For which family of elements does the melting point increase with

increasing atomic mass?

1. alkali metals

2. halogens

(A) 1 only

(B) 2 only

(C) both 1 and 2

(D) neither 1 nor 2

3. Which pair of substances could be separated by a simple distillation in

a school laboratory?

(A) ammonia and argon

(B) salt and water

(C) oil and vinegar

(D) flour and sugar

4. Which compound is least soluble in water?

(A) Al(NO3)3

(B) Na3PO4

(C) K2SO4

(D) PbCl2

5. An object is dried by heating it in an oven. Which procedure would give

the most accurate determination of its mass?

(A) The object is weighed while it is still warm.

(B) The object is weighed after being cooled on the laboratory bench.

(C) The object is weighed after being cooled in a desiccator.

(D) The object is weighed after being cooled by blowing air on it.

6. A sample of gas is to be identified by means of its behavior in the

presence of a glowing splint. Which gas will neither itself burn nor cause

the splint to burn?

(A) oxygen

(B) nitrogen

(C) hydrogen

(D) methane

7. A compound prepared as a model of hemoglobin is 4.6% iron by mass. If

the compound is known to contain a single iron atom, which of these values

will be closest to its molar mass?

(A) 1000 g mol¯1

(B) 1200 g mol¯1

(C) 1400 g mol¯1

(D) 1600 g mol¯1

8. How many hydrogen atoms are present in 0.046g of ethanol, C2H5OH? (Molar

Mass of C2H5OH is 46 g mol¯1)

(A) 6.0 x 1020

(B) 1.2 x 1021

(C) 3.0 x 1021

(D) 3.6 x 1021

9. Which of these hydrated salts contains the greatest percentage of water

by mass?

(A) BaCl2 · 2H2O

(B) CuSO4 · 5H2O

(C) CaCl2 · 6H2O

(D) Ni(ClO4)2 · 6H2O

10. Ammonium dichromate, (NH4)2Cr2O7, decomposes when heated to produce N2,

H2O, and Cr2O3 as represented by this equation.

__(NH4)2Cr2O7(s) ---> __N2(g) + __H2O(g) + __Cr2O3(s)

What is the coefficient for H2O when this equation is correctly balanced

using the smallest set of whole number coefficients?

(A) 1

(B) 2

(C) 4

(D) 8

11. What volume of 0.15 M HCl can be made from 7.5 mL of concentrated HCl

(12M)?

(A) 0.060 L

(B) 0.60 L

(C) 6.0 L

(D) 6.0 x 102 L

12. Hematite, Fe2O3, is the most common iron ore. How many moles of

hematite are in an ore sample that contains 355 g of iron? Assume hematite

is the only source of iron in this ore.

(A) 1.11 mol

(B) 1059 mol

(C) 3.18 mol

(D) 6.36 mol

13. How many moles of Mg(OH)2 can be precipitated when 15 mL of 0.20 M

MgCl2 solution is mixed with 25 mL of 0.18 M KOH?

(A) 0.0015 mol

(B) 0.0022 mol

(C) 0.0030 mol

(D) 0.0045 mol

14. A 2.0 mL sample of HCl(g) is mixed with a 1.5 mL of NH3(g). What is the

volume if the resulting mixture after the reaction is complete? (Assume all

measurements are carried out at the same pressure and temperature and that

the volume of the solid is negligible)

HCl(g) + NH3(g) ---> NH4Cl(s)

(A) 0.5 mL

(B) 1.5 mL

(C) 2.0 mL

(D) 3.5 mL

15. A student wants to prepare 250. mL of 0.10 M NaCl solution. Which

procedure is most appropriate? (The molar mass of NaCl is 58.4 g mol¯1)

(A) Add 5.84 g of NaCl to 250. mL of H2O

(B) Add 1.46 g of NaCl to 250. mL of H2O

(C) Dissolve 5.84 g of NaCl in 50 mL of H2O and dilute to 250. mL.

(D) Dissolve 1.46 g of NaCl in 50 mL of H2O and dilute to 250. mL.

16. Which set of temperature and pressure conditions will cause a gas to

exhibit the greatest deviation from ideal gas behavior?

(A) 100 °C and 4 atm

(B) 100 °C and 2 atm

(C) -100 °C and 4 atm

(D) 0 °C and 2 atm

17. A mixture of 0.5 mol of CH4, 0.5 mol of H2 and 0.5 mole of SO2 is

introduced into a 10.0 L container at 25 °C. If the container has a pinhole

leak, which describes the relationship between the partial pressures of the

individual components in the container after 3 hours?

(A) PSO2 > PCH4 > PH2

(B) PSO2 < PCH4 < PH2

(C) PSO2 < PCH4 > PH2

(D) PSO2 = PCH4 = PH2

18. Which factor affects the vapor pressure of a liquid?

(A) Temperature

(B) atmosphereic pressure

(C) Volume of the liquid

(D) surface area of the liquid

19. A 500 mL gas sample is collected over water at a pressure of 740mmHg

and 25 °C. What is the volume of the dry gas at STP? (STP = 1 atm and 0 °C)

Vapor Pressure at 25 ° of H2O equals 24mmHg

20. For a single substance at a specific temperature, which of these

characteristics shows the greatest difference when compared among the

solid, liquid, and gas phases?

(A) kinetic energy of the molecules in the solid and liquid phases

(B) kinetic energy of the molecules in the liquid and gas phases

(C) distance between the molecules in the solid and liquid phases

(D) distance between the molecules in the liquid and gas phases

21. Which of these substances, when in the solid phase, is expected to have

the weakest intermolecular forces?

(A) Ca

(B) C

(C) CaC2

(D) CO2

22. Carbon reacts with oxygen according to this equation.

2C(s) + O2(g) ---> 2CO(g)

DH = -220 kJ

Which statements are true?

1. The reaction is exothermic.

2. The combustion of 0.50 mol of carbon produces 55 kJ of heat energy

(A) 1 only

(B) 2 only

(C) both 1 and 2

(D) neither 1 nor 2

23. Which has the greatest absolute entropy?

(A) one mol of C(s) at 25 °C

(B) one mol of CH3Cl(l) at 25 °C

(C) one mol of C2H6(g) at 25 °C

(D) one mol of C6H6(l) at 25 °C

24.

Reaction DH°, kJ mol¯1

(1/2) N2(g) + (1/2) O2(g) ---> NO(g) 90.2 kJ mol¯1

(1/2) N2(g) + O2(g) ---> NO2(g) 33.2 kJ mol¯1

Use these data to calculate DH° for this reaction.

NO(g) + (1/2) O2(g) ---> NO2(g)

(A) -57.0

(B) -28.5

(C) +28.5

(D) +57.0

25. A 1.0 g sample of substance A at 100 °C is added to 100 ml of H2O at 25

°C. Using separate 100 mL portions of H2O, the procedure is repeated with

substance B and then with substance C. How will the final temperatures of

the water compare?

Substance Specific Heat

A 0.60 J g¯1 °C¯1

B 0.40 J g¯1 °C¯1

C 0.20 J g¯1 °C¯1

(A) Tc > Tb > Ta

(B) Tb > Ta > Tc

(C) Ta > Tb > Tc

(D) Ta = Tb = Tc

26. How many grams of benzene, C6H6(l), must be burned in a bomb

calorimeter to raise its temperature by 1.5 °C? Given: The calorimeter

constant is 12.59 kJ C¯1 and the DH°:combustion for C6H6 = -491 kJ g¯1

(A) 0.45 g

(B) 2.8 g

(C) 3.3 g

(D) 8.4 g

27. 2N2O5 (g) ---> 4NO2(g) + O2(g)

What is the ratio of the rate of decomposition of N2O5 to the rate of the

formation of NO2?

(A) 1:2

(B) 2:1

(C) 1:4

(D) 4:1

28. When reacted with water, the insecticides DDT decomposes with a half-

life of 10 years. Approximately how many years will it take for 99% of a

given sample to decompose once exposed to water in the environment?

(A) 50 yr

(B) 70 yr

(C) 500 yr

(D) 700 yr

29. Which property, if decreased, will cause an increase in the rate of a

reaction involving a solid?

(A) temperature

(B) pressure

(C) concentration

(D) particle size

30. Which graph corresponds to the change in concentration of a reacant

that is a first order reaction?

31.Which reaction characteristics are changing by the addition of a

catalyst to a reaction to a reaction at constant temperature?

1. activation energy

2. equilibrium concentrations

3. reaction enthalpy

(A) 1 only

(B) 3 only

(C) 1 and 2 only

(D) 1, 2, and 3

32. Which reation characteristics will be affected by a change in

temperature?

1. value of equilibrium constant

2. equilibrium concentrations

(A) 1 only

(B) 2 only

(C) 1 and 2 only

(D) neither 1 nor 2

33. A water solution of sodium carbonate, Na2CO3, has a pH greater than 7

because

(A) it contains more carbonate ions than water molecules.

(B) it contains more sodium ions than carbonate ions.

(C) sodium ions react with water.

(D) carbonate ions react with water.

34. Which species dissociates most completely in water solution?

(A) NH4+

(B) H2CO3

(C) HNO3

(D) HSO4¯

35. When one mole of (NH4)2HPO4(s) dissolves in water, the number of moles

of ions present is closest to which value?

(A) 16

(B) 8

(C) 4

(D) 3

36. The dissociation constant for a certian weak monoprotic acid is 9.0 x

10¯5. What is the [H+] of a 0.10 M solution of this weak acid that is 0.010

M in the sodium salt of the acid?

(A) 9.0 x 10¯6

(B) 9.0 x 10¯4

(C) 3.0 x 10¯3

(D) 3.0 x 10¯2

37. According to Bronsted-Lowry Theory, which of these species cannot be

amphoteric?

(A) NH4+(aq)

(B) NH3(aq)

(C) NH2¯(aq)

(D) NH2¯(aq)

38. Which of these solutions, appropriately combined, could be used to

produce a buffer?

(A) HCI and NaOH

(B) HNO2 and NaNO3

(C) KI and KOH

(D) HF and NaOH

39. The solubility of PbI2 is 0.0013 mol L¯1. Use this information to find

the Ksp for PbI2.

(A) 1.7 x 10¯6

(B) 6.8 x 10¯6

(C) 2,2 x 10¯9

(D) 8.8 x 10¯9

40. For this reaction, E°cell = 0.79 V.

6 I¯(aq) + Cr2O72¯(aq) + 14 H+ ---> 3 I2 (aq) + 2 Cr3+(aq) + 7 H2O(aq)

Given that the standard reduction potential for

Cr2O72¯(aq) ---> 2Cr3+ (aq) is 1.33 V, what is E°red for I2(aq)?

(A) +0.54 V

(B) -0.54 V

(C) +0.18 V

(D) -0.18 V

41. What is the product formed at the anode in the electrolysis of 1.0 M

NaNO3(aq)?

(A) H2(g)

(B) NO2(g)

(C) O2(g)

(D) Na(s)

42. Which of these ions is the best reducing agent?

Standard Reduction Potentials, E°

Fe3+(aq) + e¯ ---> Fe2+(aq) + 0.77 V

Cu2+(aq) + e¯ ---> Cu+(aq) + 0.15 V

(A) Fe3+

(B) Fe2+

(C) Cu2+

(D) Cu+

43. Zn(s) + Cl2(g, 1 atm) <===> Zn2+(aq, 1 M) + 2Cl¯(aq, 1 M) An

electrochemical cell based on this reaction has a cell voltage, E°, of 2.12

V. Which change could make the cell voltage greater than 2.12 V?

(A) add more Zn(s)

(B) add more Cl¯(aq) ions

(C) decrease the concentration of Zn2+(aq) ions

(D) decrease the partial pressure of Cl2

44. What is the total number of p orbitals completely or partially filled

in a gaseous silicon atom in its ground state?

(A) 1

(B) 2

(C) 4

(D) 5

45. What is the electron configuration of the Co3+ ion?

(A) 1s2 2s22p6 3s23p63d6

(B) 1s2 2s22p6 3s23p63d4 4s2

(C) 1s2 2s22p6 3s23p63d5 4s1

(D) 1s2 2s22p6 3s23p63d7 4s2

46. For which element is the "last electron" added to a d orbital?

(A) Ba

(B) Nd

(C) Hf

(D) Pb

47. When the species F¯, Na+, and Ne are arranged in order of increasing

energy for the removal of an electron, what is the correct order?

(A) F¯ < Na+ < Ne

(B) F¯ < Ne < Na+

(C) Na+ < Ne < F¯

(D) Ne < F¯ < Na+

48. Which electronic transition in a hydrogen atom occurs with an energy

that corresponds to visible light?

(A) n = 2 ---> n = 1

(B) n = 5 ---> n = 1

(C) n = 4 ---> n = 2

(D) n = 6 ---> n = 3

49. Which species has a Lewis electron structure with one, and only one,

unshared pair of valence electrons?

(A) NH2¯

(B) H3O+

(C) H2S

(D) CH4

50. Which compound is expected to have the lowest melting point?

(A) CsF

(B) RbF

(C) KF

(D) NaF

51. Which of these molecules does not contain two pi bonds?

(A) CO

(B) CS2

(C) H2CCO

(D) H2CCH2

52. Which arrangement shows the bonds H-H, C-C, and Si-Si in order of

increasing bond energy?

(A) Si-Si < C-C < H-H

(B) C-C < H-H < Si-Si

(C) H-H < Si-Si < C-C

(D) H-H < C-C < Si-Si

53. Which species has the same general shape as SO32¯?

(A) SO3

(B) NO3¯

(C) NF3

(D) CO32¯

54. Resonance structures describe molecular structure that have

(A) hybrid orbitals.

(B) rapid equilibria.

(C) electrons that are resonating.

(D) no suitable single Lewis-electron-dot formula.

55. What is the molecular formula of a straight-chain hydrocarbon

containing six carbon atoms and one triple bond?

(A) C6H8

(B) C6H10

(C) C6H12

(D) C6H14

56. What type of reaction is represented by this equation? C2H5OH + HCO2H -

--> HCO2C2H5 + H2O

(A) addition

(B) esterification

(C) isomerization

(D) saponification

57. Each of these compounds contains only carbon, hydrogen, and oxygen.

Which compound has the highest mass percent carbon?

(A) diethyl ether

(B) ethanal

(C) ethanoic acid

(D) propanone

58. How many isomers exist for pentane C5H12?

(A) two

(B) threea

(C) four

(D) five

59. Which pair gives two names for the same compound?

(A) fomaldehyde and methanol

(B) formic acid and ethanoic acid

(C) ethane and ethene

(D) t-butyl alcohol and 2-hydroxy-2-methylpropane

60. Which compound is most soluble in water?

(A) ethylamine

(B) chlorobenzene

(C) methyl acetate

(D) pentane

Answers

# Ans. # Ans. # Ans.

1. D 21. B 41. A

2. B 22. D 42. C

3. D 23. D 43. B

4. B 24. C 44. B

5. C 25. B 45. C

6. A 26. A 46. C

7. D 27. B 47. D

8. C 28. A 48. B

9. A 29. C 49. B

10. D 30. D 50. C

11. A 31. C 51. C

12. C 32. D 52. D

13. C 33. A 53. A

14. A 34. C 54. B

15. D 35. C 55. A

16. B 36. A 56. C

17. B 37. D 57. D

18. A 38. B 58. B

19. A 39. C 59. D

20. D 40. D 60. A

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chemistry olympaid 98 "Natioal test"

1. Which pair of substances could be separated by mixing with water and

filtering?

(A) NaNO3 and K2SO4

(B) CH3OH and CH3COCH3

(C) MgCO3 and Fe(OH)3

(D) KCl and CuS

2. Which gas produces an acidic solution when bubbled into water?

(A) NH3

(B) Cl2

(C) H2

(D) CH4

3. A dilute HCl solution is to be prepared from a more concentrated

solution. Which of pieces of glassware will give the highest level of

precision?

(A) graduated cylinder and volumetric flask

(B) two graduated cylinders

(C) pipet and graduated cylinder

(D) pipet and volumetric flask

4. Which substance is likely to show the greatest change in mass when

exposed to air?

(A) Al

(B) NaOH

(C) CaCO3

(D) SiO2

5. Which is a yellow solid?

(A) C

(B) Na

(C) S8

(D) I2

6. An alloy of gold and silver contains 38.5% silver by mass and has a

density of 14.6 g mL¯1. What is the molar concentration of silver in this

alloy?

(A) 52.1 mol L¯1

(B) 45.6 mol L¯1

(C) 3.57 mol L¯1

(D) 2.64 mol L¯1

7. As2S3 reacts with O2 to give SO2 and As2O3. What is the smallest whole

number coefficient for O2 when the equation for this reaction is balanced

correctly?

_As2S3(s) + _O2(g) ---> _As2O3(s) + _SO2(g)

(A) 3

(B) 5

(C) 7

(D) 9

8. A 0.242 g sample of potassium is heated in oxygen. The result is 0.440 g

of a crystalline compound. What is the formula of this compound?

(A) KO

(B) K2O

(C) KO2

(D) KO3

9. What volume of 3.0 M Na2SO4 must be added to 25 mL of 1.0 M BaCl2 to

produce 5.0 g of BaSO4?

(A) 7.2 mL

(B) 8.3 mL

(C) 10.0 mL

(D) 14 mL

10. These three equations describe an oxidation-reduction method for

determining dissolved oxygen in water. How many moles of S2O32¯ are

equivalent of each mole of O2?

1) 2Mn2+(aq) + 4OH¯(aq) + O2(g) ---> 2MnO2(s) + 2H2O(l)

2) MnO2(s) + 2I¯(aq) + 4H+(aq) ---> Mn2+(aq) + I2(aq) + 2H2O(l)

3) 2S2O32¯(aq) + I2(aq) ---> S4O62¯(aq) + 2I¯(aq)

(A) 0.5

(B) 1

(C) 2

(D) 4

11. A 15 mL sample of 0.20 M MgCl2 is added to 45 mL of 0.40 M AlCl3. What

is the molarity of Cl¯ ions in the final solution?

(A) 1.0 M

(B) 0.60 M

(C) 0.35

(D) 0.30 M

12. How many electrons are present in 2.0 x 10¯3 moles of 188O2¯?

(A) 1.2 x 1021

(B) 9.6 x 1021

(C) 1.2 x 1022

(D) 1.9 x 1022

13. In which change of state are covalent bonds broken?

(A) evaporation of water

(B) fusion of sodium chloride

(C) vaporization of diamond

(D) sublimation of dry ice

14. By what factor does the average velocity of a gaseous molecule increase

when the absolute temperature is doubled?

(A) 1.4

(B) 2.0

(C) 2.8

(D) 4.0

15. Which species is expected to have the highest boiling point at 1 am

pressure?

(A) O2

(B) CO

(C) CO2

(D) HCHO

16. What is the vapor pressure of a solution with a benzene to octane molar

ratio of 2:1?

Vapor Pressure at 50 °C

benzene 280 mmHg

octane 400 mmHg

(A) 120 mmHg

(B) 320 mmHg

(C) 400 mmHg

(D) 680 mmHg

17. Which halogen in its standard state has the greatest absolute entropy

per mole?

(A) F2(g)

(B) Cl2(g)

(C) Br2(l)

(D) I2(s)

18. Which combination of vapor pressure, intermolecular forces and

DHvaporization is matched correctly?

: vapor

pressure intermolecular

forces DHvaporization

(A) high weak small

(B) high strong large

(C) low weak large

(D) low strong small

19. Calculate DH° for this reaction.

C2H2(g) + 2H2(g) ---> C2H6(g)

DHcombustion, kJ mol¯1

C2H2(g) -1300

H2(g) -286

C2H6(g) -1560

(A) -312 kJ

(B) -26 kJ

(C) +26 kJ

(D) +312 kJ

20. For which process would DS° be expected to have the greatest positive

value?

(A) O2(g) + 2H2(g) ---> 2H2O(g)

(B) H2O(s) ---> H2O(l)

(C) H2(g) + I2(g) ---> 2HI(g)

(D) N2O4(g) ---> 2NO2(g)

21. (1/2) N2(g)+ (3/2) H2(g) ---> NH3(g)

For this reaction at 25 °C, DG°f is -16.5 kJ mol¯1. What is the equilibrium

constant, Keq, for this reaction at this temperature?

(A) 1.08

(B) 7.80 x 102

(C) 4.57 x 106

(D) 2.98 x 1034

22. What are the signs for DH, DS, and DG for the freezing of liquid water

at -10 °C?

DH DS DG

(A) + - +

(B) - - 0

(C) - + -

(D) - - -

23. Which of these factors affect the value of the specific rate constant

for the reaction 2A(g) ---> B(g)?

I concentration

II pressure

III temperature

(A) I, II, and III

(B) I and II only

(C) II and III only

(D) III only

24. Which statement about work and heat is true?

(A) A given quantity of heat can be completely converted to work.

(B) Heat and work are both state functions.

(C) Some heat is always produced when work is done.

(D) Work is a state function, whereas heat is not.

25. The reaction between KMnO4 and H2C2O4 can be followed by monitoring the

disappearance of the purple color of the MnO4¯ ion. These data were

obtained for the reaction carried out at a constant temperature of 25 °C.

Exp [MnO4¯] [H2C2O4] Initial Rate,

Disappearance

of MnO4¯ (aq), M s¯1

1 1.08 x 10¯2 M 1.98 M 5.4 x 10¯5

2 1.08 x 10¯2 M 3.97 M 1.1 x 10¯4

3 2.17 x 10¯2 M 1.98 M 2.1 x 10¯4

Specify the order of this reaction with respect to [MnO4¯] and [H2C2O4]

[MnO4¯] [H2C2O4]

(A) 1st order 2nd order

(B) 2nd order 1st order

(C) 1st order 1st order

(D) 2nd order 2nd order

26. For which reaction order is the half-life independent of the initial

concentration?

I first order

II second order

(A) I only

(B) II only

(C) both I and II

(D) neither I nor II

27. What is the activation energy for the reverse of this reaction?

N2O4(g) ---> 2NO2(g)

Data for the given reaction is: DH = + 54.0 kJ and Ea = +57.2 kJ.

(A) -54.0 kJ

(B) +3.2 kJ

(C) +60.2 kJ

(D) +111.2 kJ

28. How does an increase in temperature affect the rates of the foward and

reverse reactions for an exothermic reaction?

rate of foward reaction rate of reverse reaction

(A) increases increases

(B) increases decreases

(C) decreases increases

(D) increases remains the same

29. The reaction between chloroform, CHCl3(g), and chlorine, Cl2(g), to

form CCl4(g) and HCl(g) is believed to occur by this series of steps.

Step 1 Cl2 ---> Cl(g) + Cl(g)

Step 2 CHCl3(g) + Cl(g) ---> CCl3(g) + HCl(g)

Step 3 CCl3(g) + Cl(g) ---> CCl4(g)

If this reaction is first order in CHCl3 and half order in Cl2, which

statement about the relative rates of step 1, 2, and 3 is correct?

(A) Step 1 is the slowest.

(B) Steps 1 and 2 must both be slow.

(C) Step 2 must be slower than step 1.

(D) Step 3 must be the slowest

30. This reaction occurs readily above 500 °C.

2HgO(s) ---> 2Hg(l) + O2(g)

What is the equilibrium for this reaction?

(A) K = [Hg]2[O2] / [HgO]2

(B) K = [Hg][O2] / [HgO]

(C) K = [Hg]2[O2]

(D) K = [O2]

31. Consider this equilibrium, for which DH < 0.

HgO(s) + 4I¯(aq) + H2O(l) <===> HgI42¯ + 2OH¯

Which changes will increase the equilbrium concentration of HgI42¯?

I Increasing the mass of HgO(s) present

II Increasing [I¯]

III Adding 1 M HCI

(A) I only

(B) II only

(C) II and III only

(D) I, II, and III

32. The equilibrium constant for this reaction is approximately 10¯3.

HPO42¯(aq) + HCO3¯(aq) <===> H2PO4¯(aq) + CO32¯(aq)

Which is the strongest conjugate base in this reaction?

(A) HPO42¯(aq)

(B) HCO3¯(aq)

(C) H2PO4¯(aq)

(D) CO32¯(aq)

33. A weak acid, HX, has Ka = 9.0 x 10¯6. Within which range does the

percent dissociation for a 0.01 M HX solution lie?

(A) between 1.0% and 10%

(B) between 0.10% and 1.0%

(C) between 0.01% and 0.10%

(D) less than 0.01%

34. Which salt dissolves in water to produce a solution with a pH < 7?

(A) NaC2H3O2

(B) Ba(NO3)2

(C) AlCl3

(D) KClO4

35. Which mixture forms a buffer when dissolved in 1.0 L of water?

(A) 0.2 mol NaOH + 0.2 mol HBr

(B) 0.2 mol NaCl + 0.3 mol HCl

(C) 0.4 mol HNO2 + 0.2 mol NaOH

(D) 0.5 mol NH3 + 0.5 mol HCl

36. The equilibrium constant for this reaction is 3.6 x 10¯7

OCl¯(aq) + H2O(l) <===> HOCl(aq) + OH¯(aq)

What is Ka for HOCl?

(A) 2.8 x 10¯8

(B) 3.6 x 10¯7

(C) 6.0 x 10¯4

(D) 2.8 x 106

37. For which titration would the use of phenophthalein introduce a

significant error?

Kindicator for phenolphthalein = 1 x 10¯9

38. When solid lead iodide is added to water, the equilibrium concentration

of I¯ becomes 2.6 x 10¯3 M. What is the Ksp for PbI2?

(A) 2.2 x 10¯9

(B) 8.8 x10¯9

(C) 1.8 x 10¯8

(D) 3.5 x 10¯8

39. When these standard half reactions are combined to give a spontaneous

reaction in a voltaic cell, what is the cell voltage?

Standard Reduction Potentials, E°

Sn2+(aq) + 2e¯ ---> Sn(s) -0.14 V

Ag+(aq) + e¯ ---> Ag(s) +0.80 V

(A) 1.74 V

(B) 1.46 V

(C) 0.94 V

(D) 0.66 V

40. How many moles of elections are transferred when this equation is

balanced with the smallest whole number coefficients?

_IO3¯ + _H2O2 + _H+ ---> _I2 + _O2 + _H2O

(A) 2

(B) 4

(C) 5

(D) 10

41. If the E°cell for a given reaction has a negative value, which gives

the correct relationships for the values of DG° and Keq?

A. DG° > 0; Keq < 1

B. DG° > 0; Keq > 1

C. DG° < 0; Keq > 1

D. DG° < 0; Keq < 1

42. When anions undergo oxidation, they move toward the

A. anode of a voltaic cell and the cathode of an electrolytic cell

B. cathode of a voltaic cell and the anode of an electrolytic cell

C. anodes of both types of cells

D. cathodes of both types of cells

43. How much time is required to produce 0.10 mol of chlorine gas during

the electrolysis of molten sodium chloride using a current of 3.0 amps?

A. 55 min

B. 110 min

C. 220 min

D. 330 min

44. The visible spectrum of the hydrogen atom consists of a series of lines

that

A. converge at low energies.

B. converge at high energies.

C. are separated by equal energies.

D. are randomly spaced.

45. When the elements C, N and Si are arranged in order of increasing first

ionization energy, which is the correct order?

A. C < N < Si

B. N < C < Si

C. Si < C < N

D. Si < N < C

46. Which is a possible set of quantum numbers for a valence electron in

ground state atom of phosphorus?

n l ml ms

A. 2 1 0 +1/2

B. 3 0 0 0

C. 3 1 -1 +1/2

D. 3 2 1 -1/2

47. These are the first eight ionization energies for a particular neutral

atom. All values are expressed in MJ mol¯1. How many valence electrons does

this atom possess?

1st 2nd 3rd 4th 5th 6th 7th 8th

1.31 3.39 5.30 7.47 10.99 13.33 71.33 84.01

A. 1

B. 2

C. 4

D. 6

48. Which gaseous ion in its ground state has the greatest number of

unpaired electrons?

A. Mn3+

B. Fe3+

C. Co3+

D. Ni3+

49. Which of these characteristics describe the PCl3 molecule?

I trigonal planar shape

II sp3 hybridized phosphorus atom

III polar bonds

IV nonpolar molecule

A. I and II only

B. II and III only

C. I and IV only

D. I, III, and IV only

50. According to the Lewis structure for the HNNH, how many sigma bonds, pi

bonds, and lone pairs of electrons are present?

sigma bonds pi bonds lone pairs of electrons

A. 2 2 2

B. 3 2 0

C. 3 1 2

D. 3 0 4

51. In the Lewis structure for the BrF4¯ ion, how many lone pairs of

electrons are placed around the central atom?

(A) 0

(B) 1

(C) 2

(D) 3

52. What term is used for the measure of an atom's attraction for the

electrons that constitute a covalent bond?

(A) ionization energy

(B) bond dissociation energy

(C) electron affinity

(D) electronegativity

53. One way of writing the Lewis structure of the cyanate ion, OCN¯, places

one double bond between the carbon atom and the oxygen atom and another

double bond between the carbon atom and the nitrogen atom. What are the

formal charges on the oxygen, carbon, and nitrogen atoms, respectively for

this structure?

(A) 0, 0, -1

(B) -1, 0, 0

(C) -1, +1, -1

(C) -2, 1, 0

54. Lithium crystallizes in a body-centered cubic unit cell. What is the

mass of one unit cell? Report your answer in grams.

(A) 1.15 x 10¯23 g

(B) 2.30 x 10¯23 g

(C) 5.75 x 10¯23 g

(D) 1.04 x 10¯22 g

55. Which compound is an isomer of 2-methylbutane?

(A) 2,2-dimethylpropane

(B) 2,2-dimethylbutane

(C) 2-methylpentane

(D) 2-metylbutene

56. How many different isomers have the molecular formula C3H6Cl2?

(A) 8

(B) 6

(C) 4

(D) 2

57. Which type of compound is most likely to be colored?

(A) acid

(B) chlorofluorocarbon

(C) ketone

(D) polyene

58. A certain four-carbon alcohol reacts with acidified potassium

dichromate to form a ketone. Which structure is most likely for that four-

carbon alcohol?

(A) H3CCH2CH2CH2OH

(B) H3CCH2CH(OH)CH3

(C) H3CC(OH)(CH3)2

(D) H2C=CHCH2CH2OH

59. What type of compound is CH3CH2OCH3?

(A) alcohol

(B) aldehyde

(C) ester

(D) ether

60. Which pair are two different names for the same compound?

(A) acetic acid and ethanoic acid

(B) formaldehyde and methanol

(C) isopropyl alcohol and 1-propanol

(D) ethene and ethyne

Answers

The answers to this set of national level chemistry is not available as of

now.If found it will be provided to u .

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chemistry olympiad:1997

1. The formula of sodium tungstate is Na2WO4 and that of lead phosphate is

Pb3(PO4)2. What is the formula for lead tungstate?

(A) PbWO4

(B) Pb2(WO4)3

(C) Pb3(WO4)2

(D) Pb3(WO4)4

2. A metal from period 4 is added to water and a vigorous reaction takes

place with the evolution of a gas. Which statements are correct?

1. Oxygen is evolved.

2. Hydrogen is evolved.

3. The resulting solution is acidic.

4. The resulting solution is basic.

(A) 1 and 3 only

(B) 2 and 3 only

(C) 2 and 4 only

(D) 1 and 4 only

3. 30.mL of 0.10 Ba(OH)2(aq) is added to 30. mL of 0.10 M H2SO4(aq) and the

solution is stirred quickly. The rise in temperature, DT1, is measured. The

experiments is repeated using 90.mL of each solution and the rise in

temperature, DT1, is measured. What is the relationship between DT1 and

DT2?

(A) DT2 is equal to DT1

(B) DT2 is three times as large as DT1

(C) DT2 is six times as large as DT1

(D) DT2 is one-third as large as DT1

4. An aqueous solution is 0.1 M in each of these ions.

1. Cu2+

2. Hg2+

3. Pb2+

Which ion(s) will precipitate if 0.1 M HCI is added?

(A) 2 only

(B) 3 only

(C) 2 and 3 only

(D) 1,2, and 3

5. The age of a wooden artifact was determined by carbon-14 dating. Three

different measurements gave values of 6925, 4815, and 5485 years. Which is

the best value to report for the age of this artifact?

(A) 5700 years

(B) 5740 years

(C) 5741 years

(D) 6000 years

6. What is the molality, m, of methanol in a solution prepared by

dissolving 160 g of methanol, CH3OH, in 200.0 g of water?

(A) 1.0 m

(B) 5.0 m

(C) 10.0 m

(D) 25.0 m

7. What is the coefficient for oxygen when this equation is balanced?

Sb2S3(s) + O2(g) ---> Sb2O3(s) + SO2(g)

(A) 9

(B) 7

(C) 5

(D) 4

8. Flourine reacts with uranium hexaflouride, UF6, as represented by this

equation.

U(s) + 3F2(g) ---> UF6(g)

How many flourine molecules are required to produce 2.0 mg of uranium

hexaflouride, UF6, from an excess of uranium? The molar mass of UF6 is

352.0 g mol¯1

(A) 3.4 x 1018

(B) 1.0 x 1019

(C) 2.0 x 1019

(D) 3.4 x 1021

9. Magnesium hydroxide, Mg(OH)2, is the white milky substance in milk of

magnesia. What mass of Mg(OH)2 is formed when 15mL of 0.18 M NaOH are

combined with 12mL of 0.14 M MgCl2? The molar mass of Mg(OH)2 is 58.3 g

mol¯1

(A) 0.079 g

(B) 0.097 g

(C) 0.16 g

(D) 0.31 g

10. What is the concentration of H+ in a solution that is prepared by

mixing 50.0 mL of 0.50 M HCl with 200.0 mL of 0.25 M HCl?

(A) 0.30 M

(B) 0.35 M

(C) 0.40 M

(D) 0.45 M

11. Which concentrations can be calculated if the mole fraction and density

of an aqueous solution of HCl are known?

1. molality

2. molarity

3. percent by mass

(A) 1 only

(B) 3 only

(C) 1 and 2 only

(D) 1, 2, and 3

12. The second law of thermodynamics states that the

(A) energy of the universe is increasing.

(B) energy of the universe is constant.

(C) entropy of the universe is increasing

(D) entropy of the universe is constant.

13. Which substance is expected to have the greatest lattice enthalpy?

(A) LiF

(B) LiI

(C) CsF

(D) CsI

14. When these substances are arranged in order of increasing boiling point

(lowest boiling point first), what is the correct order?

(A) NH3 < PH3 < AsH3

(B) AsH3 < PH3 < NH3

(C) PH3 < AsH3 < NH3

(D) AsH3 < NH3 < PH3

15. The concentration of copper(II) ions in an unknown solution is

determined by comparing the absorbance of a diluted sample of the unknown

with the Beer's Law Plot at a constant wave length for several standard

solutions. When a 2.0 mL sample of the unknown copper(II) ion solution is

diluted to 5.0 mL, its absorbance is 0.29. What is the concentration of

copper(II) ions in the unknown?

(A) 0.0062 M

(B) 0.012 M

(C) 0.031 M

(D) 0.078 M

16. Which values can be obtained from the information represented by the

vapor pressure curve of a liquid?

1. normal boiling point

2. normal freezing point

3. enthalpy of vaporization

(A) 1 only

(B) 1 and 2 only

(C) 1 and 3 only

(D) 1, 2, and 3

17. The enthalpy of fusion of ice is 6.02 kJ mol¯1. The heat capacity of

water is 4.18 J g¯1 °C¯1. What is the smallest number of ice cubes at O°C,

each containing one mole of water, that are needed to cool 500. g of liquid

water from 20°C to O°C?

(A) 1

(B) 7

(C) 14

(D) 125

18. As O2(l) is cooled at 1 atm pressure, it freezes to form Solid I at

54.5 K. At a lower temperature, Solid I rearranges to Solid II, which has a

different crystal structure. Thermal measurements show that for the phase

transition Solid I to Solid II, DH= -743.1 J mol¯1 and DS = -17.0 J K¯1

mol¯1. At what temperature are solids I and II in equilibrium?

(A) 2.06 K

(B) 31.5 K

(C) 43.7 K

(D) 53.4 K

19. What will happen to the state of a substance represented by this phase

diagram when its temperature and pressure are changed from 60°C and 0.2 atm

to 40°C and 1.0 atm?

(A) liquid to solid

(B) gas to solid

(C) solid to liquid

(D) solid to gas

20. All are state functions except

(A) pressure.

(B) heat.

(C) free energy.

(D) enthalpy.

21. Use the bond energies in the table to estimate DH for this reaction.

H2C=CH2 + Cl2 --> ClH2C-CH2Cl

Bond Energies

C - C 347 kJ mol¯1

C = C 612 kJ mol¯1

C - Cl 331 kJ mol¯1

C - H 414 kJ mol¯1

Cl - Cl 243 kJ mol¯1

(A) DH = -684 kJ

(B) DH = -154 kJ

(C) DH = +89 kJ

(D) DH = +177 kJ

22. The free energy of formation of NO is 78 kJ mol¯1 at the temperature of

an automobile engine (1000 K). What is the equilibrium constant for this

reaction at 1000 K?

(1/2) N2(g) + (1/2) O2(g) <===> NO(g)

(A) 8.4 x 10¯5

(B) 7.1 x 10¯9

(C) 4.2 x 10¯10

(D) 1.7 x 10¯19

23. For which reaction will DH= DE? Assume each reaction is carried out in

an open container.

(A) 2CO(g) + O2(g) ---> 2CO2(g)

(B) H2(g) + Br2(g) ---> 2HBr(g)

(C) C(s) + 2H2O(g) ---> 2H2(g) + CO2(g)

(D) PCl5(g) ---> PCl3(g) + Cl2(g)

24. A certain zero-order reaction has k = 0.025 M s¯1 for the disapperance

of A. What will be the concentration of A after 15 seconds if the initial

concentration is 0.50 M?

(A) 0.50 M

(B) 0.32 M

(C) 0.12 M

(D) 0.060 M

25. A first-order reaction has a half-life of 14.5 hours. What percentage

of the reactant will remain after 24.0 hours?

(A) 18.3%

(B) 31.8%

(C) 45.5%

(D) 68.2%

26. The reaction of hydrogen and iodine monochloride is represented by this

equation. P align=center>H2(g) + 2ICl(g) ---> 2HCl(g) + I2(g)

This reaction is first order in H2(g) and also first order in ICl(g). Which

of these proposed mechanisms can be consistent with the given information

about this reaction?

Mechanism 1 H2(g) + 2ICl(g) ---> 2HCl(g) + I2(g)

Mechanism 2 H2(g) + ICl(g) ---> HCl(g) + HI(g) slow

HI(g) + ICl(g) ---> HCl(g) + I2(g) fast

(A) 1 only

(B) 2 only

(C) Both 1 and 2

(D) Neither 1 nor 2

27. The reaction of ozone with oxygen atoms in the presence of chlorine

atoms can occur by the two-step process shown here with the rate constant

for each step.

O3(g) + Cl(g) ---> O2(g) + ClO(g) k1 = 5.2 x 109 L mol¯1 s¯1

ClO(g) + O(g) ---> Cl(g) + O2(g) k2 = 2.6 x 1010 L mol¯1 s¯1

Which of the values below is closest to the rate constant of the overall

net reaction, given by this equation.

O3(g) + O(g) ---> 2O2(g)

(A) 5.2 x 109 L mol¯1 s¯1

(B) 2.6 x 1010 L mol¯1 s¯1

(C) 3.1 x 1010 L mol¯1 s¯1

(D) 1.4 x 1020 L mol¯1 s¯1

28. The first-order reaction:

2N2(g) ---> 2N2(g) + O2(g)

has a rate constant of 1.3 x 10¯11 s¯1 at 270°C and 4.5 x 10¯10 s¯1 at

350°C. What is the activation energy for this reaction?

(A) 15 kJ

(B) 30 kJ

(C) 68 kJ

(D) 120 kJ

29. A 0.010 M solution of maleic acid, a monoportic organic acid, is 14%

ionized. What is Ka for maleic acid?

(A) 2.3 x 10¯3

(B) 2.3 x 10¯4

(C) 2.0 x 10¯4

(D) 2.0 x 10¯6

30. If 0.1 mol of each substance is added to 1 L of H2O, which substance

produces the lowest pH?

(A) Al2(SO4)3

(B) NH4C2H3O2

(C) NaNO3

(D) Na3PO4

31. For the reaction N2(g) + O2(g) <===> 2NO(g), the equilibrium constant

is K1. The equilibrium constant is K2 for the reaction 2NO(g) + O2(g) <===>

2NO2(g), What is K for this reaction?

NO2(g) <===> (1/2) N2(g) + O2(g)

(A) 1/ (K1K2)

(B) 1/ (2K1K2)

(C) 1/ (4K1K2)

(D) [1/K1K2]1/2

32. Consider the reaction represented by this equation.

CH3Cl(g) + H2O(g) ---> CH3OH(g) + HCl(g)

These kinetic data were obtained for the given reaction concentrations.

Initial Concentrations, M Initial Rate, Disappearance

of CH3Cl, M s¯1

[CH< sub>Cl] [H2O]

0.20 0.20 1.0

0.40 0.20 2.0

0.40 0.40 8.0

Based on these data, what is the rate equation for the given reaction

(A) Rate = k[CH3Cl] [H2O]

(B) Rate = k[CH3Cl]2 [H2O]

(C) Rate = k[CH3Cl] [H2O]2

(D) Rate = k[CH3Cl]2 [H2O]4

33. This equation represents the decomposition of methanol.

CH3OH(g) <===> CO(g) + 2H2(g)

The K for this reaction equals 1.26 x 10¯3

At equilibrium, a 1.0 L steel tank is found to contain 0.25 mol of CH3OH

and 0.060 mol CO. How many moles of H2 are in the tank?

(A) 0.00030 mol

(B) 0.0053 mol

(C) 0.017 mol

(D) 0.072 mol

34. A buffer solution is prepared in which the concentration of NH3 is 0.30

M and the concentration of NH4 is 0.20M. What is the pH of this solution?

The equilibrium constant, Kb for NH3 equals 1.8 x 10¯5.

(A) 8.73

(B) 9.08

(C) 9.43

(D) 11.72

35. Ka for hydrofluoric acid is 6.9 x 10¯4. What is K for this reaction?

F¯(aq) + H2O(l) ---> HF(aq) + OH¯(aq)

(A) 6.9 x 10¯11

(B) 1.4 x 10¯11

(C) 2.6 x 10¯9

(D) 8.3 x 10¯6

36. When these acids are arranged in order of increasing strength (weakest

acid first), what is the correct order?

(A) HOCl(aq) < H2SeO4(aq) < H3PO4(aq)

(B) H3PO4(aq) < H2SeO4(aq) < HOCl(aq)

(C) H2SeO4(aq) < HOCl(aq) < H3PO4(aq)

(D) HOCl(aq) < H3PO4(aq) < H2SeO4(aq)

37. The titration curves labeled 1 and 2 were obtained by titrating equal

volumes of two different acid samples with portions of the same sodium

hydroxide solution. What conclusions can be drawn about the relative

concentrations and strengths of acids 1 and 2 from these curves?

(A) The concentrations are the same but acid 1 is weaker than acid 2.

(B) The concentrations are the same but acid 1 is stronger than acid 2.

(C) Acid 1 is the same strength as acid 2, but it is less concentrated.

(D) Acid 1 is the same strength as acid 2, but it is more concentrated.

38. Some compounds that are insoluble in water dissolve in acids. Which of

these compounds is expected to be more soluble in 1.0 M HNO3 than in an

equal volume of distilled water?

1. AgCl

2. BaCO3

3. AlPO4

(A) 2 only

(B) 1 and 3 only

(C) 2 and 3 only

(D) 1,2 and 3

39. A 0.10 M solution of fluoride ions is gradually added to a solution

containing Ba2+, Ca2+, and Pb2+ ions, each at a concentration of 1 x 10¯3

M. In what order, from first to last, will the precipitates of BaF2, CaF2,

and PbF2 form?

Solubility Product, Ksp

BaF2 1.8 x 10 ¯7

CaF2 1.5 x 10 ¯10

PbF2 7.1 x 10 ¯7

(A) CaF2, PbF2, BaF2

(B) BaF2, CaF2, PbF2

(C) PbF2, BaF2, CaF2

(D) CaF2, BaF2, PbF2

40. When this oxidation-reduction equation is correctly balanced, what is

the coefficient of I¯(aq)?

__IO3¯(aq) + __I¯(aq) + __H+(aq) ---> __I2(aq) + __H2O(l)

(A) 2

(B) 4

(C) 5

(D) 8

41. Two aqueous solutions, one containing AgNO3 and the other X2+ ions, are

electrolyzed with the same amount of current for equal times. 5.00g of Ag

and 3.17g of X are deposited. What is molar mass of X?

(A) 34.3 g mol¯1

(B) 68.4 g mol¯1

(C) 137 g mol¯1

(D) 170 g mol¯1

42.

Standard Reduction Potentials, E°

H2O2(aq) + 2H+(aq) + 2e¯ ---> 2H2O(l) + 1.763V

Fe3+(aq) + e¯ ---> Fe2+(aq) + 0.769V

Given these values of standard reduction potentials, what is the value of

E° for this reaction?

H2O2(aq) + 2H+(aq) + 2Fe2+(aq) ---> 2H2O(l) + 2Fe3+(aq)

(A) 0.225V

(B) 0.994V

(C) 2.532V

(D) 3.301V

43. Consider this reaction

2Cr2+(aq) + Co2+(aq) ---> 2Cr3+(aq) + Co(s) E° = 0.126 V

If the concentrations of the Cr2+ ion and the Co2+ ion are each decreased

by a factor of 10 in separate experiments, how do the cell voltages in the

two experiments compare?

(A) The voltage change will be twice as great when [Cr2+] is decreased

as when [Co2+].

(B) The voltage change will be ten times as great when [Cr2+] is

decreased as when [Co2+].

(C) The voltage change will be the same in the two experiments, but

different from E°.

(D) The voltages wll not be changed from E°.

44. How many electrons are gained by one mole of permanganate ions when

permanganate ions react with reducing agents in acid solution to form

manganese(II) ions?

(A) 5

(B) 6.02 x 1023

(C) (6.02 x 1023) / 5

(D) 5 x 6.02 x 1023

45. In which pair do both species have the same electron configurations?

(A) Se2¯, Kr

(B) Mn2+, Cr3+

(C) Na+, Cl¯

(D) Ni, Zn2+

46. Which metal requires the least energy to exhibit the photoelectric

effect?

(A) Cs

(B) Ca

(C) Cu

(D) Hg

47. Which relationship between the radii of theses species is correct?

(A) Na < Na+; F < F¯

(B) Na > Na+; > F > F¯

(C) Na < Na+; F > F¯

(D) Na > Na+; F < F¯

{Reader's Note on #47: Answers A and B in the original are the same answer.

Answer B has been modified.]

48. Which of these species is paramagnetic?

1. Ti4+

2. Fe2+

3. Zn0

(A) 2 only

(B) 3 only

(C) 1 and 2 only

(D) 2 and 3 only

49. In how many elements does the last electron have the quantum numbers of

n = 4 and l = 1?

(A) 4

(B) 6

(C) 8

(D) 10

50. In which species is the electron pair geometry the same as the

molecular geometry?

(A) BeF2

(B) PF3

(C) SF4

(D) IF5

51. What is the nitrogen-oxygen bond order in the NO2¯ ion?

(A) 0.5

(B) 1.0

(C) 1.5

(D) 2.0

52. How many sigma and pi bonds are shown in this molecule?

(A) 4 sigma, 1 pi

(B) 4 sigma, 3 pi

(C) 5 sigma, 2 pi

(D) 5 sigma, 1 pi

53. Which of these species has unpaired electrons?

1. O2

2. O2¯

3. O22¯

(A) 2 only

(B) 3 only

(C) 1 and 2 only

(D) 1 and 3 only

54. What is the formal charge on chlorine if the compound has this Lewis

structure?

(A) 0

(B) +3

(C) +5

(D) +7

55. Penicillin N is an antibacterial agent that contains 8.92% sulfur by

mass. Which value could be the molar mass of penicillin N?

(A) 256 g.mol¯1

(B) 360 g.mol¯1

(C) 390 g.mol¯1

(D) 743 g.mol¯1

56. This is the structure of pyridine. How many hydrogen atoms are in

pyridine, what is the hybridization of the nitrogen atom, and what is the

electron geometry around nitrogen in pyridine?

(A) 4 H atoms, sp3, pyramidal

(B) 5 H atoms, sp2, planar

(C) 6 H atoms, sp2, planar

(D) 6 H atoms, sp3, pyramidal

57. How many different compounds have the formula C3H8O?

(A) one

(B) two

(C) three

(D) four

58. When these compounds are arranged in order of increasing boiling point,

what is the correct order?

1.CH3CH2CH2CH2CH3

2. CH3CH2CH(CH3)CH3

3. CH3C(CH3)2CH3

(A) 1 < 2 < 3

(B) 2 < 1 < 3

(C) 2 < 3 < 1

(D) 3 < 2 < 1

59. Many biologically-active compounds exist as two enantiomers (two non-

superimposable optical isomers), one of which is active while the other is

not. Which of these compounds could exist as optical isomers?

60. A four-carbon alcohol was oxidized with acidified potassium dichromate

to form a ketone. Which structure represents the original alcohol?

Answers

1. A 21. B 41. C

2. C 22. A 42. B

3. A 23. B 43. A

4. B 24. C 44. D

5. D 25. B 45. A

6. D 26. B 46. A

7. A 27. A 47. D

8. B 28. D 48. A

9. A 29. B 49. B

10. A 30. A 50. A

11. D 31. D 51. C

12. C 32. C 52. D

13. A 33. D 53. C

14. C 34. C 54. B

15. D 35. B 55. B

16. C 36. D 56. B

17. B 37. A 57. C

18. C 38. C 58. D

19. B 39. D 59. D

20. B 40. C 60. D

---------------------------------------------------------------------------

------------------------------

Chemistry olympaid :1996

National Test

1. What is the formula for the basic anhydride of Ba(OH)2?

(A) Ba2O

(B) BaO

(C) BaO2

(D) Ba

2. Which element exhibits both +1 and +3 oxidation numbers in its

compounds?

(A) B

(B) Be

(C) Sn

(D) Ti

3. Which element is obtained commercially by electrolysis?

(A) aluminum

(B) iron

(C) oxygen

(D) sulfur

4. A 0.1 M solution of a certain cation will form a precipitate with 0.1 M

solutions of all of these anions; OH¯, CO32¯, SO42¯. Which cation fits this

description?

(A) Ba2+

(B) Fe2+

(C) Mg2+

(D) Pb2+

5. Each of these solutions is added to a mixture of aqueous sodium bromide

and chloroform,CHCl3. Which one will give a positive test for aqueous

bromine when the solutions are vigorously mixed?

(A) NaCl solution

(B) NaI solution

(C) NaI3 solution

(D) chlorine water

6. Oxalic acid dihydrate, H2C2O4 . 2 H2O(s) is often used as a primary

standard to standardize sodium hydroxide solutions. Which of these facts

are reasons to choose this substance as a primary standard?

I. It is diprotic.

II. It is a stable compound that can be weighed directly in air.

III. It is available in a pure form.

(A) III only

(B) I and II only

(C) II and III only

(D) I, II, and III

7. When FeCl3 is ignited in an atmosphere of pure oxygen,this reaction

takes place.

4 FeCl3(s) + 3 O2(g) ---> 2 Fe2O3(s) + 6 Cl2(g)

If 3.0 mol of FeCl3 are ignited in the presence of 2.0 mol of O2 gas, how

much of which reagent is present in excess and therefore remains unreacted?

(A) 0.33 mol FeCl3 remain unreacted

(B) 0.67 mol FeCl3 remain unreacted

(C) 0.25 mol O2 remain unreacted

(D) 0.50 mol O2 remain unreacted

8. How many grams of SbF3 are needed to produce a gram of Freon-12, CCl2F2,

according to the reation represented by this equation?

3 CCl4 + 2 SbF3 ---> 3 CCl2F2+ 2 SbCl3

Substance Molar Mass

SbF3 179 g mol¯1

CCl2F2 121 g mol¯1

(A) 0.667g

(B) 0.986g

(C) 1.50g

(D) 2.22g

9. A self-contained breathing apparatus uses potassium superoxide, KO2, to

convert the carbon dioxide and water in exhaled air into oxygen, as shown

by the equation.

4 KO2(s) + 2 H2O(g) + 4 CO2(s) ---> 4 KHCO3(s) + 3 O2(g)

How many molecules of oxygen gas will be produced from the 0.0468 g of

carbon dioxide that is exhaled in a typical breath?

(A) 4.8 x 1020

(B) 6.4 x 1020

(C) 8.5 x 1020

(D) 1.9 x 1021

10. Magnetite, Fe3O4, can be converted into metallic iron by heating with

carbon monoxide as represented by this equation.

Fe3O4(s) + 4 CO(g) ---> 3 Fe(s) + 4 CO 2(g)

How many kilograms of Fe3O4 must be processed in this way to obtain 5.00 kg

of iron if the process is 85% efficient?

Substance Molar Mass

Fe3O4 232 g mol¯1

(A) 6.92 kg

(B) 8.15 kg

(C) 20.8 kg

(D) 24.4 kg

11. What is the molality of an aqueous sucrose solution that is 25.0%

sucrose, C12H22O11 by mass?

Substance Molar Mass

C12H22O11 342 g mol¯1

(A) 0.585 m

(B) 0.731 m

(C) 0.975 m

(D) 1.17 m

12. A student finds that 31.26 mL of a 0.165 M solution of barium

hydroxide, Ba(OH)2, solution is required to just neutralize 25.00 mL of a

citric acid, H3C6H5O7, solution. What is the concentration of the H3C6H5O7

solution?

(A) 0.413 M

(B) 0.309 M

(C) 0.206 M

(D) 0.138 M

13. Which Group III element is expected to have physical and chemical

properties that are the least similar to the other elements in that family?

(A) B

(B) Al

(C) Ga

(D) Tl

14. A pure gas that is 14.4% hydrogen and 85.6% carbon by mass has a

density of 2.5 g L¯1 at 0 °C and 1 atm presure. What is the molecular

formula of the gas?

(A) CH2

(B) C2H4

(C) C4H8

(D) C6H12

15. The vapor pressure of most substances increase with temperature as

depicted by this curve. Which way of plotting these data is expected to

give a straight line?

(A) 1/P versus T

(B) P versus 1/T

(C) In P versus T

(D) In P versus 1/T

16. If 0.10 mL of liquid water are introduced into a 1.0 L flask at 25 °C,

how many moles of water are in the vapor phase when equilibrium is

established?

Vapor Pressure, 25 °C

H2O 23.8 mmHg

(A) 1.28 x 10¯3

(B) 5.56 x 10¯3

(C) 1.53 x 10¯2

(D) 4.46 x 10¯2

17. Sodium chloride, NaCl, usually crystallizes in a face-centered cubic

lattice. How many Cl¯ ions are in contact with any single Na+ ion?

(A) 4

(B) 6

(C) 8

(D) 12

18. When solid NH4NO3 is dissolved in water at 25 °C, the temperature of

the solution decreases. What is true about the signs of DH and DS for this

process?

DH DS

(A)

- +

(B)

- -

(C)

+ +

(D) + -

19. If the equilibrium constant for a reaction is very small (for example,

1 x 10¯20), what would the value of DG be expected to be?

(A) a small positive number

(B) a large positive number

(C) a small negative number

(D) a large negative number

20. Use the bond energies in the table to determine DH for the formation of

hydrazine, N2H4, from nitrogen and hydrogen according to this equation:

N2(g) + 2 H2(g) ---> N2H4(g)

Bond Energies

N-N 159 kJ mol¯1

N=N 418 kJ mol¯1

N {triple bond} N 941 kJ mol¯1

H-H 436 kJ mol¯1

H-N 389 kJ mol¯1

(A) DH = 711 kJ

(B) DH = - 98 kJ

(C) DH = + 98 kJ

(D) DH = + 711 kJ

21. Use the given heats of formation to calculate the enthalpy change for

this reaction:

B2O3(s) + 3 COCl2(g) ---> 2 BCl3(g) + 3 CO2(g)

Enthalpy of Formation Data, kJ mol¯1

B2O3(s) - 1272.8

COCl2(g) - 218.8

BCl3(g) - 403.8

CO2(g) - 393.5

(A) 694.3 kJ

(B) 354.9 kJ

(C) -58.9 kJ

(D) -3917.3 kJ

22. For which of these processes is the value of DS negative?

I. Sugar is dissolved in water.

II. Steam condenses on a surface.

III. CaCO3 is decomposed into CaO and CO2.

(A) I only

(B) II only

(C) I and III only

(D) II and III only

23. What is the expected value of DG° for this reaction? (E° for the

reaction = 0.46 V)

Cu(s) + 2 Ag+(aq) ---> Cu2+(aq) + 2 Ag(s)

(A) -89 kJ

(B) -44 kJ

(C) -22kJ

(D) 15kJ

24. What is the change in internal energy, DE, for a system that does 70

joules of work as it absorbs 45 joules of heat?

(A) 115 J

(B) 25 J

(C) -25 J

(D) -115 J

25. What are the units of a second-order rate constant?

(A) sec¯1

(B) mol L¯1 sec¯1

(C) mol2 L¯2 sec¯1

(D) L mol¯1 sec¯1

26. The half life for the radioactive decay of 32P is 14.3 days. How many

days would be required for a sample of a radiopharmaceutical containing 32P

to decrease to 20% of its initial activity?

(A) 33.2 d

(B) 61.8 d

(C) 71.5 d

(D) 286 d

27. The rates of many chemical reactions double for a ten degree rise in

temperature. Which of these factors does not contribute to this change in

rate with increasing temperature?

(A) the average kinetic energy of the reactant species.

(B) the number of collisions in a given time.

(C) the number of very energetic species.

(D) the activation energy.

28. The bromination of acetone that occurs in acid solution is represented

by this question.

CH3COCH3(aq) + Br2(aq) ---> CH3COCH2Br(aq) + H+(aq) + Br¯(aq)

These kinetic data were obtained for given reaction concentrations.

Initial Concentrations, M Initial Rate,

disappearance

of Br2, M s¯1

[CH3COCH3] [Br2] [H+]

0.30 0.050 0.050 5.7 x 10¯5

0.30 0.10 0.050 5.7 x 10¯5

0.30 0.10 0.10 1.2 x 10¯4

0.40 0.050 0.20 3.1 x 10¯4

Based on these data, what is the rate equation?

(A) Rate = k[CH3COCH3][Br2][H+]

(B) Rate = k[CH3COCH3][H+]

(C) Rate = k[CH3COCH3][Br2]

(D) Rate = k[CH3COCH3][Br2][H+]2

29. What is the initial rate of the reaction (in mol L¯1 sec¯1) depicted by

this graph?

(A) 0.02

(B) 0.01

(C) 0.008

(D) 0.005

30.

2 SO2(g) + O 2(g) <===> 2 SO3(g)

Given that the equilibrium constant for the reaction above has a value of

278 at a particular temperature, what is the value of the equilibrium

constant for the following reaction at the same temperature?

SO3(g) <===> SO2(g) + 1/2 O2(g)

(A) 1.3 x 10¯5

(B) 1.8 x 10¯3

(C) 3.6 x 10¯3

(D) 6.0 x 10¯2

31.

Cl2(aq) + H2S(aq) ---> S(s) + 2 H+(aq) + 2 Cl¯(aq)

The rate equation for this reaction is: rate = k[Cl2][H2S]

Which of these mechanisms is (are) consistent with this rate equation?

I. Cl2 + H2S ---> H+ + Cl¯ + Cl+ + HS¯ (slow)

Cl+ + HS¯ ---> H+ + Cl¯ + S (fast)

II. H2S <===> H+ + HS¯ (fast equilibrium)

Cl2 + HS¯ ---> 2Cl¯ + H+ + S (slow)

(A) I only

(B) II only

(C) Both I and II

(D) Neither I or II

32. When a sample of NO2 is placed in a container, this equilibrium is

rapidly established.

2 NO2(g) <===> N2O4(g)

If this equilibrium mixture is a darker color at high temperatures and at

low pressures, which of these statements about the reaction is true?

(A) The reaction is exothermic and NO2 is darker in color than N2O4.

(B) The reaction is exothermic and N2O4 is darker in color than NO2

(C) The reaction is endothermic and NO2 is darker in color than N2O4.

(D) The reaction is endothermic and N2O4 is darker in color than NO2.

33. When the acids; H2Se, HBr, and HI, are arranged in order of increasing

strength (weakest acid first), which is the correct order?

(A) H2Se < HBr < HI

(B) HBr < HI < H2Se

(C) HBr < H2Se < HI

(D) HI < H2Se < HBr

34. Which statement is true about the relationship between Brønsted-Lowry

(B-L) bases and Lewis bases?

(A) A Lewis base must be a B-L base but a B-L base need not be a Lewis

base.

(B) A B-L base must be a Lewis base but a Lewis base need not be a B-L

base.

(C) B-L bases and Lewis bases are interchangeable.

(D) There is no relationship between Lewis and B-L bases.

35. A solution of 2.0 M formic acid (HCOOH) is 0.95% ionized. What is the

Ka of formic acid?

(A) 1.9 x 10¯2

(B) 1.8 x 10¯4

(C) 9.0 x 10¯5

(D) 4.5 x 10¯5

36. If 0.1 mol of a salt is added to 1.0 L of water, which of these salts

is expected to produce the most acidic solution?

(A) NaC2H3O2

(B) NH4NO3

(C) CuSO4

(D) AlCl3

37. The pKa values for several acid-base indicators are given in the table.

Which indicator should be used in the titration of a weak base with a

strong acid?

Indicator, pKa

2,4-dintrophenol 3.5

bromthymol blue 7.0

cresol red 8.0

alizarin yellow R 11.0

(A) 2,4-dintrophenol

(B) bromthymol blue

(C) cresol red

(D) alizarin yellow R

38. Which graph best represents the electrical conductivity behavior that

occurs when an aqueous solution of acetic acid, HC2H3O2, is titrated with

an aqueous solution of sodium hydroxide, NaOH?

39. When this oxidation-reduction equation is correctly balanced, what is

the mole ratio of reducing agent to oxidizing agent?

MnO4¯ + Sn2+ + H+ ---> Mn2+ + Sn4+ + H2O

(A) 1:1

(B) 2:1

(C) 4:1

(D) 5:2

40. The solubility of solid silver chromate, Ag2CrO4, is determined in

three solvents.

Solubility Product, Ksp

Ag2CrO4 9 x 10¯12

I. pure water

II. 0.1 M AgNO3

III. 0.1 M Na2CrO4

Predict the relative solubility of Ag2CrO4 in the three solvents.

(A) I = II = III

(B) I < II < III

(C) II = III < I

(D) II < III < I

41. Which combination of reactants will produce the greatest voltage based

on these standard electrode potentials?

Standard Reduction Potentials E°

Cu+(aq) + e¯ ---> Cu(s) + 0.52 V

Sn4+(aq) + 2e¯ ---> Sn2+(aq) + 0.15 V

Cr3+(aq) + e¯ ---> Cr2+(aq) - 0.41 V

(A) Cu+ and Sn2+

(B) Cu+ and Cr2+

(C) Cu and Sn4+

(D) Sn4+ and Cr2+

42. The reduction of oxygen gas in 1 M aqueous acid is represented by this

equation: (E° = 1.23 V)

O2(g) + 4H+(aq) + 4e¯ ---> 2H2O(l)

The potential for this reaction at physiological pH, where [H+] = 1 x 10¯7

and the partial pressure of O2 is 1 atm, will be closest to which value?

(A) 0.18 V

(B) 0.41 V

(C) 0.82 V

(D) 1.64 V

43. What products are formed during the electrolysis of a concentrated

aqueous solution of sodium chloride?

I. Cl2(g)

II. NaOH(aq)

III. H2(g)

(A) I only

(B) I and II only

(C) I and III only

(D) I, II, and III

44. A current of 5.00 A is passed through an aqueous solution of

chromium(III) nitrate for 30.0 min. How many grams of chromium metal will

be deposited at the cathode?

(A) 0.027 g

(B) 1.62 g

(C) 4.85 g

(D) 6.33 g

45. The hydrogen line spectrum provides evidence for the

(A) Heisenberg Uncertainly Principle

(B) wavelike properties of light

(C) diatomic nature of H2

(D) quantized nature of atomic energy states

46. What is the number of unpaired electrons in a manganese atom (Z = 25)

in its lowest energy states?

(A) 1

(B) 3

(C) 5

(D) 7

47. Ions with the electronic structure 1s2 2s2 2p6 3s2 3p6 would not be

present in which aqueous solution?

(A) NaF(aq)

(B) NaCl(aq)

(C) KBr(aq)

(D) CaI2(aq)

48. An element with the electron configuration [Xe]4f14 5d7 6s2, is

(A) an alkaline earth element

(B) a transition element

(C) an inert gas

(D) a rare earth

49. The neutron/proton ratio in an isotope can be increased by the emission

of

(A) an electron

(B) a neutron

(C) a gamma ray

(D) a positron

50. The bonds in ozone, O3, are best represented as

(A) distinct single and double bonds

(B) a single and a double bond that switch positions rapidly

(C) something between a single and a double bond

(D) two double bonds

51. Which pair of substances will have the most similar geometry?

(A) SO3 and SO32¯

(B) SO3 and CO32¯

(C) SO3 and SO42¯

(D) SO42¯ and CO32¯

52. What hybridization is expected for ClF3?

(A) sp3

(B) dsp2

(C) dsp3

(D) d2sp3

53. Which bond properties are consistent with one another?

Bond Order Bond Length Vibrational Frequency

(A) higher shorter higher

(B) higher longer lower

(C) lower shorter lower

(D) lower longer higher

54. Which hydrogen halide has the lowest boiling point?

(A) HF

(B) HCl

(C) HBr

(D) HI

55. Which substance has a dipole moment?

(A) CCl4

(B) CH2Cl2

(C) C2Cl2

(D) C2Cl4

56. What is the correct name for this compound?

(A) 2-ethyl-4, 4-dimethylpentane

(B) 2-methyl-4-t-butylbutane

(C) 2,2,4-trimethylhexane

(D) 1-t-butyl-2-methylbutane

57. How many different structures exist for C2H2Cl2?

(A) 1

(B) 2

(C) 3

(D) 4

58. When ethanol is heated with sulfuric acid, the major product is

(A) ethane

(B) ethene

(C) ethyne

(D) ethyl sulfate

59. Many alcohols can be oxidized to aldehydes, and aldehydes can be

oxidized to

(A) carboxylic acids

(B) esters

(C) ethers

(D) ketones

60. Which statement about polymers is not true?

(A) They are macromolecules

(B) They have simple repeating units

(C) They have very high molecular masses

(D) They are all made by chemists

Answers

# Ans. # Ans. # Ans.

1. B 21. C 41. B

2. D 22. B 42. C

3. A 23. A 43. D

4. D 24. C 44. B

5. D 25. D 45. D

6. C 26. A 46. C

7. A 27. D 47. A

8. B 28. B 48. B

9. A 29. A 49. D

10. B 30. D 50. C

11. C 31. A 51. B

12. D 32. A 52. C

13. A 33. A 53. A

14. C 34. B 54. B

15. D 35. B 55. B

16. A 36. D 56. C

17. B 37. A 57. C

18. C 38. C 58. B

19. B 39. D 59. A

20. C 40. D 60. D

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chemistry olympaid:1996

local test

1. Which gas is both diatomic and colored?

(A) carbon monoxide

(B) chlorine

(C) nitrogen dioxide

(D) oxygen

2. Which formula represents a peroxide?

(A) Li2O

(B) SiO2

(C) Na2SiO3

(D) BaO2

3. Which statement about the halogen family is true?

(A) Each of the halogens can be obtained by the electrolysis of its

respective molten halide salt.

(B) Iodine is the strongest oxidizing agent.

(C) Bromine is obtained by oxidation using chloride ions as the

oxidizing agent.

(D) Halide ions are generally more reactive than the parent halogens.

4. All of these substances are important industrial reducing agents except

(A) C

(B) CO

(C) CO2

(D) H2

5. What is the general formula for the alkali metal hydrides?

(A) MH

(B) MOH

(C) MH2

(D) M(OH)2

6. Each of three samples was weighed on a different balance. The masses of

the three are 1.028 kg, 82.9 g, and 45.1 mg. The sum of the three masses

should be reported as

(A) 1110.9451 g

(B) 1111 g

(C) 110 g

(D) 1.11 x 103 g

7. Magnetite, Fe3O4, is a mixture of iron(II) oxide and iron(III) oxide.

What is the most likely ratio of iron(II) oxide to iron(III) oxide in

magnetite?

(A) 1:1

(B) 1:2

(C) 2:3

(D) 3:2

8. A student wishes to prepare 250.mL of a 0.200 M solution of Na2SO4.

Which of these procedures should be followed?

Substance Molar Mass

Na2SO4 142 g mol¯1

(A) 28.4 g of Na2SO4 should be dissolved in 250. mL of water in a large

bottle.

(B) 250. mL of water should be added to 28.4 g of Na2SO4 in a large

bottle.

(C) 7.10 g of Na2SO4 should be dissolved in enough water to fill a

graduated beaker to the 250. mL mark.

(D) 7.10 g of Na2SO4 should be dissolved in a small amount of water and

diluted to 250. mL in a volumetric flask.

9. How many moles of ozone, O3, could be formed from 48.0 g of oxygen gas,

O2?

(A) 1.00 mol

(B) 1.30 mol

(C) 1.50 mol

(D) 2.00 mol

10. How many grams of carbon are present in 0.50 mol of sucrose

(C12H22O11)?

Substance Molar Mass

C12H22O11 342 g mol¯1

(A) 60 g

(B) 72 g

(C) 90 g

(D) 120 g

11. If excess Ca(OH)2 is treated with 0.160 mol of dry HCl gas, what is the

maximum number of grams of CaCl2 that could be formed?

Substance Molar Mass

Ca(OH)2 74.1 g mol¯1

HCl 36.5 g mol¯1

CaCl2 111.0 g mol¯1

(A) 35.5 g

(B) 17.8 g

(C) 8.88 g

(D) 4.44 g

12. What volume of 0.500 M CaCl2 solution is needed to prepare 250 mL of

solution that has a chloride concentration of 0.100 M?

(A) 12.5 mL

(B) 25.0 mL

(C) 50.0 mL

(D) 100 mL

13. Which group II element would be expected to be the hardest?

(A) Be

(B) Mg

(C) Ca

(D) Ba

14. Chlorine reacts with fluorine above 200 °C to form chlorine

trifluoride, ClF3, as shown by this equation:

Cl2(g) + 3F2(g) ---> 2ClF3(g)

If equal numbers of moles of chlorine and fluorine are combined, the

maximum number of moles of ClF3 that could be formed will be equal to

(A) the number of moles of Cl2.

(B) the number of moles of F2.

(C) twice the number of moles of Cl2.

(D) two-thirds the number of moles of F2.

15. An acidic solution of permanganate ions reacts with oxalate ions to

form manganese(II) ions and carbon dioxide, as shown in this equation.

2 MnO4¯ + 5 C2O42¯ + 16 H+ ---> 2 Mn2+ + 10 CO2 + 8 H2O

If 31.72 mL of 0.0840 M potassium permanganate solution exactly reacts with

25.00 mL of sodium oxalate solution, what is the original oxalate ion

concentration?

(A) 0.0426 M

(B) 0.107 M

(C) 0.213 M

(D) 0.266 M

16. What is true about the relative freezing points of these three

substances?

I. Water

II. 0.1 M acetic acid (HC2H3O2) solution

III. 0.1 M sodium acetate (NaC2H3O2) solution

(A) III < II < I

(B) II < III < I

(C) II = III < I

(D) II < III = I

17. Which increases as a gas is heated at constant volume?

(A) size of the molecules

(B) potential energy of the molecules

(C) kinetic energy of the molecules

(D) attractive forces between molecules

18. What is the name of the process that occurs at a system is changed from

point A to point B in this phase diagram?

(A) condensation

(B) evaporation

(C) fusion

(D) sublimation

19. When these substances (C, CO2, C6H12O6, and CaC2) are arranged in order

of increasing melting point (with the lowest melting substance first), the

correct order is

(A) C < CO2 < C6H12O6 < CaC2

(B) C6H12O6 < CaC2 < CO2 < C

(C) C < CO2 < CaC2 < C6H12O6

(D) CO2 < C6H12O6 < CaC2 < C

20. What will happen to the volume of a bubble of air found underwater in a

lake, where the temperature is 15 °C and the pressure is 1.5 atm, if the

bubble then rises to the surface where the temperature is 25 °C and the

pressure is 1.0 atm?

(A) Its volume will become greater by a factor of 2.5.

(B) Its volume will become greater by a factor of 1.6.

(C) Its volume will become greater by a factor of 1.1.

(D) Its volume will become smaller by a factor of 0.70.

21. Which of these Group IV (IUPAC Group 14) solids has the greatest

electrical conductivity at 25 degrees C?

(A) C

(B) Si

(C) Ge

(D) Pb

22. The standard enthalpy of formation ([delta]H°f) for sodium bromide is

the enthalpy change for the reaction

(A) Na+(g) + Br¯(g) --> NaBr(g)

(B) Na+(g) + Br¯(g) --> NaBr(s)

(C) 2 Na(s) + Br2(g) --> 2 NaBr(s)

(D) Na(s) + 1/2 Br2(l) --> NaBr(s)

23. Use the standard enthalpies of formation in the table to calulate

[delta]H° for this reaction:

2 CrO42¯(aq) + 2 H+(aq) --> Cr2O72¯(aq) + H2O(l)

Substance [delta]H°f, kJ mol¯1

CrO42¯(aq) - 881.2

Cr2O72¯(aq) - 1490.3

H+(aq) 0

H2O(l) - 285.8

(A) 272.1 kJ

(B) 13.7 kJ

(C) -13.7 kJ

(D) -272.1 kJ

24. For which of these processes is the value of [delta]S expected to be

negative?

I. Sugar is dissolved in water

II. Steam is condensed

III. CaCO3 is decomposed into CaO and CO2.

(A) I only

(B) I and III only

(C) II only

(D) II and III only

25. Which set of conditions is most likely to result in a reaction that is

spontaneous as written?

[delta]H [delta]S T

(A) < 0 < 0 500 °C

(B) < 0 < 0 0 °C

(C) > 0 < 0 0 °C

(D) > 0 < 0 500 °C

26. What can be correctly said about the energy of activation for a

reversible exothermic reaction? The energy of activation

(A) is greater for the reverse reaction than for the forward reaction.

(B) is greater for the forward reaction than for the reverse reaction.

(C) is the same for the reaction in both directions.

(D) for the two directions of this reaction cannot be compared without

doing experiments.

27. The reaction of nitrogen monoxide, NO, with hydrogen, H2, is

represented by this equation:

2 NO(g) + 2 H2(g) ---> N2(g) + 2 H2O(g)

The reaction obeys this rate law:

Rate = k[NO]2[H2]

If [NO] is tripled and [H2] is doubled, how will the rate be affected?

(A) The rate will be increased by a factor of six.

(B) The rate will be increased by a factor of twelve.

(C) The rate will be increased by a factor of eighteen.

(D) The rate will be increased by a factor of thirty-six.

28. Which of these changes with time for a first-order reaction?

I. rate of reaction

II. rate constant

III. half-life

(A) I only

(B) III only

(C) I and II only

(D) II and III only

29. Under certain conditions, the average rate of appearance of oxygen gas

in the reaction:

2 O3(g) ---> 3 O2(g)

is 1.2 x 10¯3 atm sec¯1. What is the average rate, expressed in units of

atm sec¯1, for the disappearance of O3?

(A) 1.2 x 10¯3

(B) 1.8 x 10¯3

(C) 8.0 x 10¯4

(D) 5.3 x 10¯3

30. The experimental data from a certain reaction gives these three graphs.

What is the most likely order for this reaction.

(A) zero

(B) first

(C) second

(D) third

31. For irreversible reactions, the rate will be affected by changes in all

of these factors except

(A) temperature.

(B) concentration of reactants.

(C) presence of a catalyst.

(D) concentration of products.

32. What is the equilibrium expression for the decomposition of ammonium

carbamate, NH4CO2NH2, that occurs according to this equation:

NH4CO2NH2(s) <===> 2 NH3(g) + CO2(g)

(A) K = [NH3][CO2]

(B) K = [NH3]2[CO2]

(C) K = [NH3][CO2] / [NH4CO2NH2]

(D) K = [NH3]2[CO2] / [NH4CO2NH2]

33. Which factors will affect both the position of equilibrium and the

value of the equilibrium constant for this reaction? The [delta]H = - 92 kJ

N2(g) + 3 H2(g) <===> 2 NH3(g)

(A) increasing the volume of the container

(B) adding N2

(C) removing NH3

(D) lowering the temperature

34. According to the Brønsted-Lowry definition, a base is a substance that

(A) increases the hydroxide ion concentration in water.

(B) can react with water to form OH¯ ions.

(C) can donate an electron pair to form a covalent bond.

(D) can accept a proton from an acid.

35. What is the pH of a 0.02 M solution of KOH?

(A) 12.3

(B) 12.0

(C) 2.0

(D) 1.7

36. Which couple is not a conjugate acid-base pair?

(A) HCO3¯ and CO32¯

(B) H3O+ and H2O

(C) H2PO4¯ and PO43¯

(D) NH3 and NH2¯

37. These acids are listed in order of decreasing acid strength in water.

HI > HNO2 > CH3COOH > HCN

According to the Brønsted-Lowry theory, which anion is the weakest base?

(A) I¯

(B) NO2¯

(C) CH3COO¯

(D) CN¯

38. What is the [H+] in a 0.40 M solution of HOCl?

Substance Equilibrium Constant, Ka

HOCl 3.5 x 10¯8

(A) 1.4 x 10¯8 M

(B) 1.2 x 10¯4 M

(C) 1.9 x 10¯4 M

(D) 3.7 x 10¯4 M

39. Which of these salts will give a basic solution when added to water?

(A) NH4NO3

(B) NH4C2H3O2

(C) Ca(NO3)2

(D) Ca(C2H3O2)2

40. BaSO4 and BaCO3 are slightly soluble salts with comparable Ksp values

in water. Which salt(s) will be more in a 1.0 M solution of HNO3 than in

water?

(A) BaSO4 only

(B) BaCO3 only

(C) both BaSO4 and BaCO3

(D) neither BaSO4 or BaCO3

41. Which change represents a reduction process?

(A) ClO¯ ---> ClO3¯

(B) N2O ---> N2O4

(C) NO ---> NH3

(D) HCrO4¯ ---> CrO42¯

42. When these species (SO2, PbS, and Na2S2O3) are listed in order of

increasing oxidation number of the sulfur atoms (most negative to most

positive oxidation number), the correct order is

(A) PbS, Na2S2O3, SO2

(B) PbS, SO2, Na2S2O3

(C) Na2S2O3, PbS, SO2

(D) SO2, Na2S2O3, PbS

43. Use these reduction potentials to determine which one of the reactions

below is spontaneous.

Reaction Reduction Potentials, E°

Ag+ + e¯ ---> Ag 0.800 V

Pb2+ + 2e¯ ---> Pb - 0.126 V

V2+ + 2e¯ ---> V - 1.18 V

(A) V2+ + 2 Ag ---> V + 2 Ag+

(B) V2+ + Pb ---> V + Pb2+

(C) 2 Ag+ + Pb2+ ---> 2 Ag + Pb

(D) 2 Ag+ + Pb ---> 2 Ag + Pb2+

44. It is possible to produce chlorine gas by electrolyzing any of these

chlorine-containing compounds under the proper conditions. Which compound

will require the smallest number of coulombs to produce one mole of

chlorine?

(A) Ca(OCl)2

(B) NaClO2

(C) KClO3

(D) Mg(ClO4)2

45. A monatomic species that has 18 electrons and a net charge of 2¯ has

(A) the same number of electrons as a neutral argon atom.

(B) more protons than electrons.

(C) 2 unpaired electrons.

(D) 20 protons

46. Based on its electron configuration, the element that is most similar

in chemical properties to selenium is

(A) As

(B) Cl

(C) Sb

(D) Te

47. How many electrons in a silver atom have n = 3 and l = 2 ?

(A) 2

(B) 8

(C) 10

(D) 18

48. The neutral atom with the largest radius is

(A) K

(B) Mg

(C) As

(D) Br

49. Which of these electron diagrams could represent the ground state of

the p valence electrons of carbon?

50. All of these molecules are polar except

(A) H2O

(B) CO2

(C) NO2

(D) SO2

51. Which species contains a central atom with sp2 hybridization?

(A) NI3

(B) CIF3

(C) O3

(D) I3¯

52. Electrostatic forces between oppositely charges are greatest in

(A) CaO

(B) MgO

(C) CaS

(D) MgS

53. Which substance has the lowest boiling point?

(A) HCl

(B) H2S

(C) PH3

(D) SiH4

54. How do the magnitudes of the H-N-H bond angles vary in these species?

(A) NH2¯ < NH3 < NH4+

(B) NH2¯ < NH4+ < NH3

(C) NH3 < NH2¯ < NH4+

(D) NH3 < NH4+ < NH2¯

55. Which molecule has the greatest bond energy

(A) CO

(B) O2

(C) NO

(D) F2

56. Which formula most likely represents an alkene?

(A) C2H2

(B) C3H8

(C) C4H8

(D) C6H6

57. All of these classes of compounds contain a carbonyl functional group

except

(A) carboxylic acids.

(B) amides.

(C) ethers.

(D) ketones.

58. How many different compounds have the formula C5H12?

(A) 2

(B) 3

(C) 4

(D) 5

59. An ester is formed by the reaction between

(A) two acids.

(B) two alcohols.

(C) two aldehydes.

(D) an acid and an alcohol.

60. Which of these is formed by condensation polymerization?

I. Nylon

II. Teflon®

(A) I only

(B) II only

(C) both I and II

(D) neither I nor II

Answers

# Ans. # Ans. # Ans.

1. B 21. D 41. C

2. D 22. D 42. A

3. A 23. C 43. D

4. C 24. C 44. A

5. A 25. B 45. A

6. B 26. A 46. D

7. B 27. C 47. C

8. D 28. A 48. A

9. A 29. C 49. D

10. B 30. B 50. B

11. C 31. D 51. C

12. B 32. B 52. B

13. A 33. D 53. D

14. D 34. D 54. A

15. D 35. A 55. A

16. A 36. C 56. C

17. C 37. A 57. C

18. D 38. B 58. B

19. D 39. D 59. D

20. B 40. B 60. A

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chemistry olympaid:1995

1. Which gas could be collected over water?

(A) ammonia

(B) carbon dioxide

(C) hydrogen chloride

(D) oxygen

2. When sodium oxide, Na2O, is added to water, the major products expected

are

(A) Na+ and OH¯ ions

(B) Na+ ions and H2O

(C) Na+ and O2¯ ions

(D) Na+ and OH¯ ions, and O2 gas

3. Which metal will react most vigorously with water?

(A) Na

(B) K

(C) Mg

(D) Ca

4. When 21.410 g of copper are added to a graduated cylinder containing

12.5 mL of water, the volume rises to 14.9 mL. What is the density of

copper?

(A) 8.9208 g mL¯1

(B) 8.921 g mL¯1

(C) 8.92 g mL¯1

(D) 8.9 g mL¯1

5. Which of these gases is least abundant in the Earth's atmosphere?

(A) argon

(B) carbon monoxide

(C) nitrogen

(D) oxygen

6. The percentage of water in a hydrated salt is to be determined by

weighing a sample of the hydrate, heating it to drive off the water, and

weighing the anhydrous product. Which procedural error(s) could result in a

percentage of water that is too low?

Procedural Mistakes

I. not heating the hydrate long enough

II. weighing the anhydrous sample while it is still warm

III. using a balance tht reads 0.12 g high for both weighings

(A) I only

(B) II only

(C) I and II only

(D) I and III only

7. How many grams of Ba(OH)2 . 8H20 (molar mass = 315.4 g mol¯1) are needed

to prepare 250. mL of solution in which the [OH¯] = 0.180 M?

(A) 28.4

(B) 14.2

(C) 7.10

(D) 3.86

8. Ammonia is prepared by the Haber Process.

N2 + 3 H2 <===> 2 NH3

If 2 mol of N2 and 3 mol of H2 are combined, the amount of NH3 that would

be formed if all of the limiting reactant were used up is known as the

(A) limited yield

(B) percent yield

(C) product yield

(D) theoretical yield

9. Calculate the percent by mass of hydrogen in diethylamine, (C2H5)2NH.

(A) 11.3%

(B) 13.7%

(C) 15.2%

(D) 23.6%

10. The insecticide Lindane®, has the emperical formula, CHCl. How many

carbon atoms does each Lindane molecule contain?

Molar Mass of Lindane = 290.8 g mol¯1

(A) 2

(B) 3

(C) 4

(D) 6

11. 2.0 x 10¯3 mol of a chlorine containing compound, when placed in water,

reacted completely with 40.0 cm3 of 0.1 M AgNO3. The compound could be

(A) NaCl

(B) MgCl2

(C) AlCl3

(D) TiCl4

12. Which reaction will produce a precipitate when 0.1 M aqueous solutions

are mixed?

(A) NaOH + H2S --->

(B) CaCl2 + K2CO3 --->

(C) Al(NO3)3 + Na2SO4 --->

(D) CuSO4 + NH4Cl --->

13. What volume of oxygen gas (O2), is measured at 0 °C and 1 atm, is

needed to completely burn 1 L of propane (C3H8) measured at the same

onditions?

(A) 10 L

(B) 7 L

(C) 6 L

(D) 5 L

14. The number of moles of KOH in 500 mL of solution to be determined by

titrating 10.00 mL portions of the KOH solution with 0.115 M HCl solution.

If 18.72 mL of the HCl solution are needed to titrate each 10.00 mL portion

of the KOH solution, how many moles of KOH are present in the original

solution?

(A) 0.00215 mol

(B) 0.00430 mol

(C) 0.108 mol

(D) 0.215 mol

15. A certain element, Z, reacts with oxygen to form the compound Z2O5. If

0.364 g of the element form 0.552 g of the compound, what is the atomic

molar mass of the element?

(A) 12.3 g mol¯1

(B) 74.6 g mol¯1

(C) 77.4 g mol¯1

(D) 153 g mol¯1

16. Which gas would be expected to have a density less than that of argon

under the same conditions?

I. carbon dioxide

II. chlorine

III. oxygen

(A) II only

(B) III only

(C) I and II only

(D) I, II, and III

17. How will the vapor pressure and the boiling temperature of H2O be

affected by the addition of NaCl?

Vapor Pressure Boiling Temperature

(A) decreases increases

(B) decreases decreases

(C) increases decreases

(D) increases increases

18. When 1.2 g of sulfur is melted with 15.0 g of naphthalene, the solution

freezes at 77.88 °C. What is the molar mass (in g mol¯1) of this form of

sulfur?

Data for Naphthtalene

Melting point, m.p. 80.00 °C

Freezing point depression

constant, kf -6.80 °C m¯1

(A) 82

(B) 118

(C) 256

(D) 560

19. An 81.4 mL sample of H2 is collected over water at 23.0 °C and 752.3

mmHg. How many moles of H2 are present?

Vapor pressure at 23.0 °C for H2O equals 21.1 mmHg

(A) 1.61 x 10¯3 mol

(B) 3.22 x 10¯3 mol

(C) 3.70 x 10¯3 mol

(D) 6.44 x 10¯3 mol

20. Equal moles of hydrogen and oxygen gas are placed in a container with a

pinhole through which both can escape. What fraction of the oxygen escapes

in the time required for one-half of the hydrogen to escape?

(A) 1/8

(B) 1/4

(C) 3/8

(D) 1/2

21. For which of these processes is the sign of the enthalpy change

different from the others?

(A) Al2O3(s) ---> 2 Al(s) + 3/2 O2(g)

(B) H2O(s) ---> H2O(l)

(C) Cl2(g) ---> 2Cl(g)

(D) Cl(g) + e¯ ---> Cl¯(g)

22. The standard ethalpy of formation (DH°) for nitrogen(IV) oxide is the

enthalpy change for the reaction

(A) N(g) + 2O(g) ---> NO2(g)

(B) 1/2 N2(g) + O2(g) ---> NO2(g)

(C) 1/2 N2O4(g) ---> NO2(g)

(D) NO(g) + 1/2 O2 ---> NO2(g)

23. In a bomb calorimeter, reactions are carried out at

(A) constant volume.

(B) constant pressure.

(C) 1 atm pressure and 25 °C.

(D) 1 atm pressure and 0 °C.

24. For the process O2(g) ---> 2 O(g), [delta]H° = +498 kJ.

What would be predicted for the sign of [delta]Srxn and the conditions

under which this reaction would be spontaneous?

[delta]Srxn Spontaneous

(A) positive at low temperatures only

(B) positive at high temperatures only

(C) negative at high temperatures only

(D) negative at low temperatures only

25. For the reaction

NH4Cl(s) --> NH3(g) + HCl(g)

[delta]H° = +176kJ and [delta]G° = +91.2 kJ at 298 K. What is the value of

[delta]G at 1000 K?

(A) -109 kJ

(B) -64 kJ

(C) +64 kJ

(D) +109 kJ

26. Consider the reaction

Hg(l) + 2 Ag+(aq) ---> Hg2+(aq) + 2 Ag(s)

What is the enthalpy change for this reaction if [delta]H°f for Ag+ (aq) is

+105.6 kJ mol¯1 and for Hg2+ (aq) is +171.1 kJ mol¯1?

(A) 65.5 kJ are evolved per mole of Hg.

(B) 65.5 lK are absorbed per mole of Hg.

(C) 40.1 kJ are evolved per mole of Hg.

(D) 40.1 kJ are absorbed per mole of Hg.

27. For the reaction

2 H2O2(aq) ---> 2 H2O(aq) + O2(g)

How does the value of [delta][H2O2] / [delta] t compare with that of

[delta][O2] / [delta] t?

(A) [delta][H2O2] / [delta] t = [delta] [O2] / [delta] t

(B) - [delta][H2O2] / [delta] t = [delta] [O2] / [delta] t

(C) [delta] [H2O2] / [delta] t = 2[delta] [O2] / [delta] t

(D) - [delta][H2O2] / [delta] t = 2[delta] [O2] / [delta] t

28. Which is (are) constant over the course of a first order reaction?

I. reaction rate

II. rate constant

(A) I only

(B) II only

(C) Both I and II

(D) Neither I nor II

29. A wooden splint that glows in air burns when place in a test tube of

oxygen beause the oxygen

(A) serves as a catalyst

(B) increases the temperature.

(C) is at a higher concentration in the test tube.

(D) has a higher order when it is pure.

30. For a first order reaction that has a half-life of 72 s at 80 °C, what

is the value of the rate constant, k?

(A) 9.6 x 10¯3 s¯1

(B) 6.2 x 10¯3 s¯1

(C) 4.2 x 10¯3 s¯1

(D) 1.4 x 10¯3 s¯1

31. What is the activation energy for a reaction if its rate doubles when

the temperature is raised from 20 °C to 35 °C?

(A) 342 kJ mol¯1

(B) 269 kJ mol¯1

(C) 34.7 kJ mol¯1

(D) 15.1 kJ mol¯1

32. Which of these changes has no effect on the equilibrium position of a

given reaction?

(A) concentration

(B) temperature

(C) use of a catalyst

(D) partial pressure of a gaseous reactant

33. Consider this reaction

P4(s) + 6 Cl2(g) <===> 4 PCl3(l)

The correct Kc expression for this reaction is

(A) Kc = 1 / [Cl2]6

(B) Kc = [PCl3]4 / [P4][Cl2]6

(C) Kc = [PCl3]4 / [Cl2]6

(D) Kc = [P4][Cl2]6 / [PCl3]4

34. Consider this equilibrium system.

CaCO3(s) <===> CaO(s) + CO2(g)

If this system is at equilibrium, which of the following will occur if some

solid CaCO3 is added to it?

I. The partial pressure of the CO2 will increase.

II. The mass of the solid CaO will decrease.

III. The system will remain unchanged.

(A) I only

(B) II only

(C) I and II only

(D) III only

35. The Ksp of CuCl is 1.9 x 10¯7 at 25 °C. What is the solubility of CuCl

in mol L¯1?

(A) 3.6 x 10¯14

(B) 1.9 x 10¯7

(C) 4.4 x 10¯4

(D) 8.8 x 10¯4

36. At 0 °C the ion product constant of water, Kw, is 1.2 x 10¯15. The pH

of pure water at this temperature is

(A) 6.88

(B) 7.00

(C) 7.46

(D) 7.56

37. What is the [H+] in a 0.010 M solution of HCN?

The equilibrium constant, Ka, for HCN equals 6.2 x 10¯10

(A) 3.6 x 10¯3 M

(B) 2.5 x 10¯6 M

(C) 1.0 x 10¯7 M

(D) 6.2 x 10¯10 M

38. HCN (aq) + HCO3¯ (aq) <===> CN¯ (aq) + H2CO3 (aq)

If the value of the equilibrium constant, K, is less than 1, what is the

strongest base in this system?

(A) HCN

(B) HCO3¯

(C) CN¯

(D) H2CO3

39. A 0.100 M solution of acetic acid (Ka = 1.8 x 10¯5) is titrated with a

0.1000 M solution of NaOH. What is the pH when 50% of the acid has been

neutralized?

(A) 2.38

(B) 4.74

(C) 5.70

(D) 7.00

40. The conjugate acid of the bicarbonate ion, HCO3¯, in H2O is

(A) H3O+

(B) CO32¯

(C) OH¯

(D) H2CO3

41. The sodium salt, NaA, of a weak acid is dissolved in water and no other

substance is added. Which of the following statements is corrected?

(A) [H+] = [A¯]

(B) [H+] = [OH¯]

(C) [A¯] = [OH¯]

(D) [HA] = [OH¯]

42. Which of these ions is predicted to produce the most acidic solution

when dissolved in H2O?

(A) K+

(B) Ba2+

(C) Co2+

(D) Fe3+

43. When 0.10 M solutions of the solutes; HClO4, NH4Br, KOH, KCN, are

arranged in order in increasing [H+], the correct order is

(A) KOH < KCN < NH4Br < HClO4

(B) KCN < KOH < HClO4 < NH4Br

(C) HClO4 < NH4Br < KCN < KOH

(D) NH4Br < HClO4 < KOH < KCN

44. Which indicator is most appropriate for titrating a 0.100 M solution of

NH3 with 0.100 M HNO3?

The equilibrium constant, Ka, for NH3 equals 1.8 x 10¯5

Indicator pH color transition range

(A) cresol red 1-2

(B) methyl red 4-6

(C) phenolphthalein 8-10

(D) alizarin yellow 10-12

45. Based on everyday chemical knowledge, which metal is the most easily

oxidized?

(A) Fe

(B) Pb

(C) Ag

(D) Na

46. In which pair does the named substance have the same oxidation number?

(A) sulfur in H2S2O7 and H2SO4

(B) mercury in Hg2+ and Hg22+

(C) oxygen in Na2O2 and H2O

(D) cobalt in Co(NH3)63+ and Co(NO3)2

47. The electrochemical series uses this reaction as a standard.

2 H+ + 2 e¯ --> H2

In order for this half cell to have a potential of 0.00 V, all of the

following are required except

(A) a solution with [H+] concentration = 1.0 M

(B) hydrogen gas at a pressure of 1.0 atm.

(C) an external source of electrons

(D) an electrode made of an inert metal such as platinum.

48. What mass of platinum could be plated on an electrode from the

electrolysis of a Pt(NO3)2 solution with a current of 0.500 A for 55.0 s?

(A) 27.8 mg

(B) 55.6 mg

(C) 45.5 mg

(D) 91.0 mg

49. Which principal quantum number transition in a hydrogen atom will

release the greatest amount of energy?

(A) 1 ---> 3

(B) 3 ---> 5

(C) 4 ---> 2

(D) 6 ---> 4

50. Which element in its ground state has the greatest number of unpaired

electrons?

(A) V (Z = 23)

(B) Fe (Z = 26)

(C) In (Z = 49)

(D) As (Z = 33)

51. For which element are the oxidation states given actually observed and

the boldface state the most stable?

(A) Ca (Z = 20) +1, +2

(B) Cr (Z = 24) +2, +3, +6

(C) In (Z = 49) +3, +5

(D) Pb (Z = 82) +2, +4

52. Which property decreases from left to right across the periodic table?

(A) electron affinity

(B) electrical conductivity

(C) ionization energy

(D) maximum oxidation state

53. When the elements; S, Se and Cl are arranged in order of increasing

atomic radius, the correct order is

(A) Se < S < Cl

(B) S < Cl < Se

(C) Cl < S < Se

(D) S < Se < Cl

54. Which bond is most polar?

(A) F-F

(B) F-O

(C) F-Cl

(D) F-S

55. Which molecule is polar?

(A) SO2

(B) CO2

(C) XeF2

(D) PCl5

56. Which electron-dot structure is most suitable for the thiocyanate ion,

SCN¯?

57. When the carbon-oxygen bonds in the species below are arranged in order

of increasing length (shortest first), what is the correct order?

I. CH3OH

II. CO2

III. CH3CO2¯

(A) I < II < III

(B) II < III < I

(C) III < II < I

(D) III < I < II

58. Which species can be described as having sp3d hybridization?

I. PCl5

II. SF4

III. I3¯

(A) I only

(B) II only

(C) I and II only

(D) I, II and III

59. Which substance is expected to have the lowest boiling point?

(A) Si

(B) SiC

(C) SiO2

(D) Si4H10

60. How many sigma bonds and how many pi bonds are represented in this

structure?

sigma bonds pi bonds

(A) 6 3

(B) 7 2

(C) 8 1

(D) 9 0

Answers

# Ans. # Ans. # Ans.

1. D 21. D 41. D

2. A 22. B 42. D

3. B 23. A 43. A

4. D 24. B 44. B

5. B 25. A 45. D

6. A 26. C 46. A

7. C 27. D 47. C

8. D 28. B 48. A

9. C 29. C 49. C

10. D 30. A 50. B

11. B 31. C 51. D

12. B 32. C 52. B

13. D 33. A 53. C

14. C 34. D 50. D

15. C 35. C 55. A

16. B 36. C 56. A

17. A 37. B 57. B

18. C 38. C 58. D

19. B 39. B 59. D

20. A 40. D 60. A

---------------------------------------------------------------------------

------------------------------

chemistry olympaid:1997(US National test)this is given under the link 1994

on the website.

1. The formula of sodium tungstate is Na2WO4 and that of lead phosphate is

Pb3(PO4)2. What is the formula for lead tungstate?

(A) PbWO4

(B) Pb2(WO4)3

(C) Pb3(WO4)2

(D) Pb3(WO4)4

2. A metal from period 4 is added to water and a vigorous reaction takes

place with the evolution of a gas. Which statements are correct?

1. Oxygen is evolved.

2. Hydrogen is evolved.

3. The resulting solution is acidic.

4. The resulting solution is basic.

(A) 1 and 3 only

(B) 2 and 3 only

(C) 2 and 4 only

(D) 1 and 4 only

3. 30.mL of 0.10 Ba(OH)2(aq) is added to 30. mL of 0.10 M H2SO4(aq) and the

solution is stirred quickly. The rise in temperature, DT1, is measured. The

experiments is repeated using 90.mL of each solution and the rise in

temperature, DT1, is measured. What is the relationship between DT1 and

DT2?

(A) DT2 is equal to DT1

(B) DT2 is three times as large as DT1

(C) DT2 is six times as large as DT1

(D) DT2 is one-third as large as DT1

4. An aqueous solution is 0.1 M in each of these ions.

1. Cu2+

2. Hg2+

3. Pb2+

Which ion(s) will precipitate if 0.1 M HCI is added?

(A) 2 only

(B) 3 only

(C) 2 and 3 only

(D) 1,2, and 3

5. The age of a wooden artifact was determined by carbon-14 dating. Three

different measurements gave values of 6925, 4815, and 5485 years. Which is

the best value to report for the age of this artifact?

(A) 5700 years

(B) 5740 years

(C) 5741 years

(D) 6000 years

6. What is the molality, m, of methanol in a solution prepared by

dissolving 160 g of methanol, CH3OH, in 200.0 g of water?

(A) 1.0 m

(B) 5.0 m

(C) 10.0 m

(D) 25.0 m

7. What is the coefficient for oxygen when this equation is balanced?

Sb2S3(s) + O2(g) ---> Sb2O3(s) + SO2(g)

(A) 9

(B) 7

(C) 5

(D) 4

8. Flourine reacts with uranium hexaflouride, UF6, as represented by this

equation.

U(s) + 3F2(g) ---> UF6(g)

How many flourine molecules are required to produce 2.0 mg of uranium

hexaflouride, UF6, from an excess of uranium? The molar mass of UF6 is

352.0 g mol¯1

(A) 3.4 x 1018

(B) 1.0 x 1019

(C) 2.0 x 1019

(D) 3.4 x 1021

9. Magnesium hydroxide, Mg(OH)2, is the white milky substance in milk of

magnesia. What mass of Mg(OH)2 is formed when 15mL of 0.18 M NaOH are

combined with 12mL of 0.14 M MgCl2? The molar mass of Mg(OH)2 is 58.3 g

mol¯1

(A) 0.079 g

(B) 0.097 g

(C) 0.16 g

(D) 0.31 g

10. What is the concentration of H+ in a solution that is prepared by

mixing 50.0 mL of 0.50 M HCl with 200.0 mL of 0.25 M HCl?

(A) 0.30 M

(B) 0.35 M

(C) 0.40 M

(D) 0.45 M

11. Which concentrations can be calculated if the mole fraction and density

of an aqueous solution of HCl are known?

1. molality

2. molarity

3. percent by mass

(A) 1 only

(B) 3 only

(C) 1 and 2 only

(D) 1, 2, and 3

12. The second law of thermodynamics states that the

(A) energy of the universe is increasing.

(B) energy of the universe is constant.

(C) entropy of the universe is increasing

(D) entropy of the universe is constant.

13. Which substance is expected to have the greatest lattice enthalpy?

(A) LiF

(B) LiI

(C) CsF

(D) CsI

14. When these substances are arranged in order of increasing boiling point

(lowest boiling point first), what is the correct order?

(A) NH3 < PH3 < AsH3

(B) AsH3 < PH3 < NH3

(C) PH3 < AsH3 < NH3

(D) AsH3 < NH3 < PH3

15. The concentration of copper(II) ions in an unknown solution is

determined by comparing the absorbance of a diluted sample of the unknown

with the Beer's Law Plot at a constant wave length for several standard

solutions. When a 2.0 mL sample of the unknown copper(II) ion solution is

diluted to 5.0 mL, its absorbance is 0.29. What is the concentration of

copper(II) ions in the unknown?

(A) 0.0062 M

(B) 0.012 M

(C) 0.031 M

(D) 0.078 M

16. Which values can be obtained from the information represented by the

vapor pressure curve of a liquid?

1. normal boiling point

2. normal freezing point

3. enthalpy of vaporization

(A) 1 only

(B) 1 and 2 only

(C) 1 and 3 only

(D) 1, 2, and 3

17. The enthalpy of fusion of ice is 6.02 kJ mol¯1. The heat capacity of

water is 4.18 J g¯1 °C¯1. What is the smallest number of ice cubes at O°C,

each containing one mole of water, that are needed to cool 500. g of liquid

water from 20°C to O°C?

(A) 1

(B) 7

(C) 14

(D) 125

18. As O2(l) is cooled at 1 atm pressure, it freezes to form Solid I at

54.5 K. At a lower temperature, Solid I rearranges to Solid II, which has a

different crystal structure. Thermal measurements show that for the phase

transition Solid I to Solid II, DH= -743.1 J mol¯1 and DS = -17.0 J K¯1

mol¯1. At what temperature are solids I and II in equilibrium?

(A) 2.06 K

(B) 31.5 K

(C) 43.7 K

(D) 53.4 K

19. What will happen to the state of a substance represented by this phase

diagram when its temperature and pressure are changed from 60°C and 0.2 atm

to 40°C and 1.0 atm?

(A) liquid to solid

(B) gas to solid

(C) solid to liquid

(D) solid to gas

20. All are state functions except

(A) pressure.

(B) heat.

(C) free energy.

(D) enthalpy.

21. Use the bond energies in the table to estimate DH for this reaction.

H2C=CH2 + Cl2 --> ClH2C-CH2Cl

Bond Energies

C - C 347 kJ mol¯1

C = C 612 kJ mol¯1

C - Cl 331 kJ mol¯1

C - H 414 kJ mol¯1

Cl - Cl 243 kJ mol¯1

(A) DH = -684 kJ

(B) DH = -154 kJ

(C) DH = +89 kJ

(D) DH = +177 kJ

22. The free energy of formation of NO is 78 kJ mol¯1 at the temperature of

an automobile engine (1000 K). What is the equilibrium constant for this

reaction at 1000 K?

(1/2) N2(g) + (1/2) O2(g) <===> NO(g)

(A) 8.4 x 10¯5

(B) 7.1 x 10¯9

(C) 4.2 x 10¯10

(D) 1.7 x 10¯19

23. For which reaction will DH= DE? Assume each reaction is carried out in

an open container.

(A) 2CO(g) + O2(g) ---> 2CO2(g)

(B) H2(g) + Br2(g) ---> 2HBr(g)

(C) C(s) + 2H2O(g) ---> 2H2(g) + CO2(g)

(D) PCl5(g) ---> PCl3(g) + Cl2(g)

24. A certain zero-order reaction has k = 0.025 M s¯1 for the disapperance

of A. What will be the concentration of A after 15 seconds if the initial

concentration is 0.50 M?

(A) 0.50 M

(B) 0.32 M

(C) 0.12 M

(D) 0.060 M

25. A first-order reaction has a half-life of 14.5 hours. What percentage

of the reactant will remain after 24.0 hours?

(A) 18.3%

(B) 31.8%

(C) 45.5%

(D) 68.2%

26. The reaction of hydrogen and iodine monochloride is represented by this

equation. P align=center>H2(g) + 2ICl(g) ---> 2HCl(g) + I2(g)

This reaction is first order in H2(g) and also first order in ICl(g). Which

of these proposed mechanisms can be consistent with the given information

about this reaction?

Mechanism 1 H2(g) + 2ICl(g) ---> 2HCl(g) + I2(g)

Mechanism 2 H2(g) + ICl(g) ---> HCl(g) + HI(g) slow

HI(g) + ICl(g) ---> HCl(g) + I2(g) fast

(A) 1 only

(B) 2 only

(C) Both 1 and 2

(D) Neither 1 nor 2

27. The reaction of ozone with oxygen atoms in the presence of chlorine

atoms can occur by the two-step process shown here with the rate constant

for each step.

O3(g) + Cl(g) ---> O2(g) + ClO(g) k1 = 5.2 x 109 L mol¯1 s¯1

ClO(g) + O(g) ---> Cl(g) + O2(g) k2 = 2.6 x 1010 L mol¯1 s¯1

Which of the values below is closest to the rate constant of the overall

net reaction, given by this equation.

O3(g) + O(g) ---> 2O2(g)

(A) 5.2 x 109 L mol¯1 s¯1

(B) 2.6 x 1010 L mol¯1 s¯1

(C) 3.1 x 1010 L mol¯1 s¯1

(D) 1.4 x 1020 L mol¯1 s¯1

28. The first-order reaction:

2N2(g) ---> 2N2(g) + O2(g)

has a rate constant of 1.3 x 10¯11 s¯1 at 270°C and 4.5 x 10¯10 s¯1 at

350°C. What is the activation energy for this reaction?

(A) 15 kJ

(B) 30 kJ

(C) 68 kJ

(D) 120 kJ

29. A 0.010 M solution of maleic acid, a monoportic organic acid, is 14%

ionized. What is Ka for maleic acid?

(A) 2.3 x 10¯3

(B) 2.3 x 10¯4

(C) 2.0 x 10¯4

(D) 2.0 x 10¯6

30. If 0.1 mol of each substance is added to 1 L of H2O, which substance

produces the lowest pH?

(A) Al2(SO4)3

(B) NH4C2H3O2

(C) NaNO3

(D) Na3PO4

31. For the reaction N2(g) + O2(g) <===> 2NO(g), the equilibrium constant

is K1. The equilibrium constant is K2 for the reaction 2NO(g) + O2(g) <===>

2NO2(g), What is K for this reaction?

NO2(g) <===> (1/2) N2(g) + O2(g)

(A) 1/ (K1K2)

(B) 1/ (2K1K2)

(C) 1/ (4K1K2)

(D) [1/K1K2]1/2

32. Consider the reaction represented by this equation.

CH3Cl(g) + H2O(g) ---> CH3OH(g) + HCl(g)

These kinetic data were obtained for the given reaction concentrations.

Initial Concentrations, M Initial Rate, Disappearance

of CH3Cl, M s¯1

[CH< sub>Cl] [H2O]

0.20 0.20 1.0

0.40 0.20 2.0

0.40 0.40 8.0

Based on these data, what is the rate equation for the given reaction

(A) Rate = k[CH3Cl] [H2O]

(B) Rate = k[CH3Cl]2 [H2O]

(C) Rate = k[CH3Cl] [H2O]2

(D) Rate = k[CH3Cl]2 [H2O]4

33. This equation represents the decomposition of methanol.

CH3OH(g) <===> CO(g) + 2H2(g)

The K for this reaction equals 1.26 x 10¯3

At equilibrium, a 1.0 L steel tank is found to contain 0.25 mol of CH3OH

and 0.060 mol CO. How many moles of H2 are in the tank?

(A) 0.00030 mol

(B) 0.0053 mol

(C) 0.017 mol

(D) 0.072 mol

34. A buffer solution is prepared in which the concentration of NH3 is 0.30

M and the concentration of NH4 is 0.20M. What is the pH of this solution?

The equilibrium constant, Kb for NH3 equals 1.8 x 10¯5.

(A) 8.73

(B) 9.08

(C) 9.43

(D) 11.72

35. Ka for hydrofluoric acid is 6.9 x 10¯4. What is K for this reaction?

F¯(aq) + H2O(l) ---> HF(aq) + OH¯(aq)

(A) 6.9 x 10¯11

(B) 1.4 x 10¯11

(C) 2.6 x 10¯9

(D) 8.3 x 10¯6

36. When these acids are arranged in order of increasing strength (weakest

acid first), what is the correct order?

(A) HOCl(aq) < H2SeO4(aq) < H3PO4(aq)

(B) H3PO4(aq) < H2SeO4(aq) < HOCl(aq)

(C) H2SeO4(aq) < HOCl(aq) < H3PO4(aq)

(D) HOCl(aq) < H3PO4(aq) < H2SeO4(aq)

37. The titration curves labeled 1 and 2 were obtained by titrating equal

volumes of two different acid samples with portions of the same sodium

hydroxide solution. What conclusions can be drawn about the relative

concentrations and strengths of acids 1 and 2 from these curves?

(A) The concentrations are the same but acid 1 is weaker than acid 2.

(B) The concentrations are the same but acid 1 is stronger than acid 2.

(C) Acid 1 is the same strength as acid 2, but it is less concentrated.

(D) Acid 1 is the same strength as acid 2, but it is more concentrated.

38. Some compounds that are insoluble in water dissolve in acids. Which of

these compounds is expected to be more soluble in 1.0 M HNO3 than in an

equal volume of distilled water?

1. AgCl

2. BaCO3

3. AlPO4

(A) 2 only

(B) 1 and 3 only

(C) 2 and 3 only

(D) 1,2 and 3

39. A 0.10 M solution of fluoride ions is gradually added to a solution

containing Ba2+, Ca2+, and Pb2+ ions, each at a concentration of 1 x 10¯3

M. In what order, from first to last, will the precipitates of BaF2, CaF2,

and PbF2 form?

Solubility Product, Ksp

BaF2 1.8 x 10 ¯7

CaF2 1.5 x 10 ¯10

PbF2 7.1 x 10 ¯7

(A) CaF2, PbF2, BaF2

(B) BaF2, CaF2, PbF2

(C) PbF2, BaF2, CaF2

(D) CaF2, BaF2, PbF2

40. When this oxidation-reduction equation is correctly balanced, what is

the coefficient of I¯(aq)?

__IO3¯(aq) + __I¯(aq) + __H+(aq) ---> __I2(aq) + __H2O(l)

(A) 2

(B) 4

(C) 5

(D) 8

41. Two aqueous solutions, one containing AgNO3 and the other X2+ ions, are

electrolyzed with the same amount of current for equal times. 5.00g of Ag

and 3.17g of X are deposited. What is molar mass of X?

(A) 34.3 g mol¯1

(B) 68.4 g mol¯1

(C) 137 g mol¯1

(D) 170 g mol¯1

42.

Standard Reduction Potentials, E°

H2O2(aq) + 2H+(aq) + 2e¯ ---> 2H2O(l) + 1.763V

Fe3+(aq) + e¯ ---> Fe2+(aq) + 0.769V

Given these values of standard reduction potentials, what is the value of

E° for this reaction?

H2O2(aq) + 2H+(aq) + 2Fe2+(aq) ---> 2H2O(l) + 2Fe3+(aq)

(A) 0.225V

(B) 0.994V

(C) 2.532V

(D) 3.301V

43. Consider this reaction

2Cr2+(aq) + Co2+(aq) ---> 2Cr3+(aq) + Co(s) E° = 0.126 V

If the concentrations of the Cr2+ ion and the Co2+ ion are each decreased

by a factor of 10 in separate experiments, how do the cell voltages in the

two experiments compare?

(A) The voltage change will be twice as great when [Cr2+] is decreased

as when [Co2+].

(B) The voltage change will be ten times as great when [Cr2+] is

decreased as when [Co2+].

(C) The voltage change will be the same in the two experiments, but

different from E°.

(D) The voltages wll not be changed from E°.

44. How many electrons are gained by one mole of permanganate ions when

permanganate ions react with reducing agents in acid solution to form

manganese(II) ions?

(A) 5

(B) 6.02 x 1023

(C) (6.02 x 1023) / 5

(D) 5 x 6.02 x 1023

45. In which pair do both species have the same electron configurations?

(A) Se2¯, Kr

(B) Mn2+, Cr3+

(C) Na+, Cl¯

(D) Ni, Zn2+

46. Which metal requires the least energy to exhibit the photoelectric

effect?

(A) Cs

(B) Ca

(C) Cu

(D) Hg

47. Which relationship between the radii of theses species is correct?

(A) Na < Na+; F < F¯

(B) Na > Na+; > F > F¯

(C) Na < Na+; F > F¯

(D) Na > Na+; F < F¯

{Reader's Note on #47: Answers A and B in the original are the same answer.

Answer B has been modified.]

48. Which of these species is paramagnetic?

1. Ti4+

2. Fe2+

3. Zn0

(A) 2 only

(B) 3 only

(C) 1 and 2 only

(D) 2 and 3 only

49. In how many elements does the last electron have the quantum numbers of

n = 4 and l = 1?

(A) 4

(B) 6

(C) 8

(D) 10

50. In which species is the electron pair geometry the same as the

molecular geometry?

(A) BeF2

(B) PF3

(C) SF4

(D) IF5

51. What is the nitrogen-oxygen bond order in the NO2¯ ion?

(A) 0.5

(B) 1.0

(C) 1.5

(D) 2.0

52. How many sigma and pi bonds are shown in this molecule?

(A) 4 sigma, 1 pi

(B) 4 sigma, 3 pi

(C) 5 sigma, 2 pi

(D) 5 sigma, 1 pi

53. Which of these species has unpaired electrons?

1. O2

2. O2¯

3. O22¯

(A) 2 only

(B) 3 only

(C) 1 and 2 only

(D) 1 and 3 only

54. What is the formal charge on chlorine if the compound has this Lewis

structure?

(A) 0

(B) +3

(C) +5

(D) +7

55. Penicillin N is an antibacterial agent that contains 8.92% sulfur by

mass. Which value could be the molar mass of penicillin N?

(A) 256 g.mol¯1

(B) 360 g.mol¯1

(C) 390 g.mol¯1

(D) 743 g.mol¯1

56. This is the structure of pyridine. How many hydrogen atoms are in

pyridine, what is the hybridization of the nitrogen atom, and what is the

electron geometry around nitrogen in pyridine?

(A) 4 H atoms, sp3, pyramidal

(B) 5 H atoms, sp2, planar

(C) 6 H atoms, sp2, planar

(D) 6 H atoms, sp3, pyramidal

57. How many different compounds have the formula C3H8O?

(A) one

(B) two

(C) three

(D) four

58. When these compounds are arranged in order of increasing boiling point,

what is the correct order?

1.CH3CH2CH2CH2CH3

2. CH3CH2CH(CH3)CH3

3. CH3C(CH3)2CH3

(A) 1 < 2 < 3

(B) 2 < 1 < 3

(C) 2 < 3 < 1

(D) 3 < 2 < 1

59. Many biologically-active compounds exist as two enantiomers (two non-

superimposable optical isomers), one of which is active while the other is

not. Which of these compounds could exist as optical isomers?

60. A four-carbon alcohol was oxidized with acidified potassium dichromate

to form a ketone. Which structure represents the original alcohol?

Answers

1. A 21. B 41. C

2. C 22. A 42. B

3. A 23. B 43. A

4. B 24. C 44. D

5. D 25. B 45. A

6. D 26. B 46. A

7. A 27. A 47. D

8. B 28. D 48. A

9. A 29. B 49. B

10. A 30. A 50. A

11. D 31. D 51. C

12. C 32. C 52. D

13. A 33. D 53. C

14. C 34. C 54. B

15. D 35. B 55. B

16. C 36. D 56. B

17. B 37. A 57. C

18. C 38. C 58. D

19. B 39. D 59. D

20. B 40. C 60. D

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------------------------------

chemistry olympaid :1993

1. Which diagram is the best representation for a mixture of hydrogen and

helium at 25 °C and 1 atm?

2. Which combination of 1 M solutions will produce a visible reaction when

mixed?

Solution Mixtures:

I. HCl and Pb(NO3)2

II. HCl and NaOH

III. HCl and Na2CO3

(A) I and II only

(B) I and III only

(C) II and III only

(D) I, II, III

3. Which physical property would be most useful for determining whether two

samples of metal are the same metal?

(A) mass

(B) volume

(C) color

(D) density

4. Which technique could be used to separate a homogeneous mixture?

Techniques:

I. chromatography

II. distillation

III. filtration

(A) I only

(B) III only

(C) I and II only

(D) I, II, III

5. How many of these elements are liquids at 25 °C and 1 atm?

Elements:

mercury

phosphorus

radon

(A) 0

(B) 1

(C) 2

(D) 3

6. What is the mole fraction of methanol, CH3OH, in a solution of methanol

and water that contains 50 g of each?

Substance Molar Mass

CH3OH 32 g mol¯1

H2O 18 g mol¯1

(A) 0.18

(B) 0.36

(C) 0.50

(D) 0.64

7. Ammonia can be reacted with oxygen to form nitrogen(II) oxide and water

according to the unbalanced equation

_NH3 + _O2 ---> _ NO + _H2O

When this equation is balanced with the simplest set of whole number

coefficients, the coefficients are

(A) 1,1,1,1

(B) 2,1,2,3

(C) 2,5,2,3

(D) 4,5,4,6

8. A lab manual directs a student to measure a piece of ribbon 5.00 cm long

and calculate its mass from the mass of 100.00 cm of the ribbon (0.985 g).

Why is this approach superior to simply cutting a 5.00 cm piece of ribbon

and determining its mass on an electronic milligram balance?

(A) Magnesium ribbon can corrode the balance pan as it is being weighed

(B) Such a small piece of ribbon will not give a readout on a milligram

balance

(C) The length can be measured more rapidly than the mass

(D) Measuring its length gives a more precise mass

9. What should be done to prepare 500.0 mL of a 0.200 M solution of NaCl?

The Molar Mass of NaCl is 58.45 g mol¯1

(A) 11.7 g of NaCl should be dissolved in 500.0 mL of H2O

(B) 11.7 g of NaCl should be dissolved in sufficient H2O to give a

total volume of 500.0 mL

(C) 5.85 g of NaCl should be dissolved in sufficient H2O to give a

total volume of 500.0 mL

(D) 2.92 g of NaCl should be dissolved in 500.0 mL of H2O

10. Equal masses of O2 and N2 are reacted according to this equation:

O2 + N2 ---> 2 NO

Which statement is true?

(A) O2 is the limiting reagent and N2 is present in excess

(B) N2 is the limiting reagent and O2 is present in excess

(C) all of the O2 and N2 react and neither is in excess

(D) Nothing can be said about the limiting reagent

11. When a 0.817 g sample of a copper oxide is heated with excess hydrogen

gas, 0.187 g of water is formed. What is the apparent formula of the copper

oxide?

(A) CuO

(B) Cu2O

(C) Cu2O3

(D) CuO2

12. A reaction in which DS and DH are positive is expected to be

(A) nonspontaneous under all conditions

(B) spontaneous under all conditions

(C) more spontaneous at low temperatures

(D) more spontaneous at high temperatures

13. Which process or reaction has a positive DH?

(A) H2O(l) ---> H2O(s)

(B) 2 CH3OH(l) + 3 O2(g) ----> 2 CO2(g) + 4 H2O(l)

(C) CO2(s) ---> CO2(g)

(D) 2 Na(s) + Cl2(g) ---> 2 NaCl (s)

14. For which process or reaction is DS positive at 25 °C?

(A) 2 NO2(g) ---> N2O4(g)

(B) CO2(g) ---> CO2(s)

(C) CH4(g) + 2 O2(g) ---> CO2(g) + 2 H2O(l)

(D) 2 SO3(g) --- > 2 SO2(g) + O2(g)

15. For the reaction

H2(g) + I2(s) ---> 2 HI(g) DHrxn = 53.0 kJ

What will be the value of DHrxn (in kJ) for this reaction ?

HI(g) ---> 1/2 H2(g) + 1/2 I2(s)

(A) 26.5

(B) 7.3

(C) -26.5

(D) -53.0

16. For the reaction of hydrogen peroxide and iodide ion in acid solution,

represented by the equation:

H2O2 + 3I¯ + 2H+ ---> I3¯ + 2 H2O

these kinetic data are gathered:

Initial Concentrations, M

H2O2 I¯ H+ Initial Rate, M s¯1

Exp. 1 0.010 0.010 0.00050 1.15 x 10¯6

Exp. 2 0.020 0.010 0.00050 2.30 x 10¯6

Exp. 3 0.020 0.020 0.00050 4.60 x 10¯6

Exp. 4 0.020 0.020 0.00100 4.60 x 10¯6

What is the rate law for the reaction?

(A) Rate = k [H2O2] [I¯]

(B) Rate = k [H2O2] [I¯] [H+]

(C) Rate = k [H2O2]2 [I¯]

(D) Rate = k [H2O2] [I¯]2

17. A small increase in temperature often causes a large increase in the

rate of a chemical reaction. This effect is best attributed to

(A) a decrease in the activation energy of the reaction

(B) more frequent collisions at the higher temperature

(C) the occurrence of more collisions with the needed energy

(D) different reaction pathways at the higher temperature

18. Zinc metal reacts with excess HCl according to the equation:

Zn(s) + 2H+(aq) + 2Cl¯(aq) ----> Zn2+(aq) + 2Cl¯(aq) + H2(g)

Which change will increase the rate of evolution of H2?

Changes in Reaction Conditions

I. using zinc dust in place of chunks

II. using 2 M HCl in place of 1 M HCl

III. using 200 mL of 1 M HCl in place of 100 mL

(A) I only

(B) I and II only

(C) II and III only

(D) I, II, and III

19. Which of the indicated quantities in the reaction diagram will be

affected by the addition of a catalyst?

(A) I only

(B) II only

(C) I and II only

(D) I and III only

20. Gases can be compressed more easily than liquids because

(A) gas molecules are larger than liquid molecules

(B) molecules move more slowly in gases than in liquids

(C) average intermolecular distances are greater in gases

(D) intermolecular forces increase as gas molecules are brought closer

together

21. A mixture of N2 (0.40 mol), O2 (0.50 mol) and Ne (0.30 mol) exerts a

pressure of 740 mmHg. What would be the pressure of the N2 alone at the

same temparature in the same container (in mmHg)?

(A) 740

(B) 400

(C) 333

(D) 247

22. At pressures below its triple point a substance can exist

(A) only as a gas.

(B) only as a solid.

(C) as a solid or a liquid.

(D) as a solid or a gas.

23. When a beaker of pure water is boiling vigorously, the bubbles that

rise to the surface are composed primarily of

(A) air.

(B) hydrogen.

(C) hydrogen and oxygen.

(D) water vapor.

24. If the pressure of an ideal gas sample is tripled while the temperature

is halved, which expression best describes the final volume?

(A) Vfinal = 0.06 x Vinitial

(B) Vfinal = 0.167 x Vinitial

(C) Vfinal = 0.667 x Vinitial

(D) Vfinal = 1.5 x Vinitial

25. A compound boils at 45 °C, does not conduct electricity appreciably as

a pure liquid but produces an electrically-conducting solution when

dissolved in water. When this substance is cooled below its freezing point

(16 °C), what type of solid is formed?

(A) ionic

(B) metallic

(C) molecular

(D) network covalent

26. Chemical equilibrium is defined as the point when

(A) all reaction ceases.

(B) products and reactants are formed at equal rates.

(C) reactants are all converted to products.

(D) reactants and products are present at equal concentrations.

27. Which is true for a reaction with an equilibrium constant of 3.0 x

10¯15?

(A) The reactants are favored.

(B) The products are favored.

(C) Equilibrium will be reached slowly.

(D) Equilibrium will be reached rapidly.

28. The exothermic formation of ClF3 is represented by the equation:

Cl2(g) + 3 F2(g) <===> 2 ClF3(g) DH = -329 kJ

Which change will increase the quatity of ClF3 in an equilibrium mixture of

Cl2, F2, and ClF3?

(A) increasing the temperature

(B) removing Cl2

(C) increasing the volume of the container

(D) adding F2

29. Which will be the same for solutions of 0.50 M NH3 and 0.50 M NaOH?

Solution Variables:

I. concentration of OH¯ ion

II. volume of 0.20 M HCl required for neutralization

(A) I only

(B) both I and II

(C) II only

(D) neither I nor II

30. The solubility of which salt will be increased the most in 1 M HCl

(relative to its solubility in H2O)?

(A) BaCO3

(B) PbCl2

(B) NaNO3

(D) CuSO4

31. Which is the strongest acid?

(A) HF

(B) HNO2

(C) H2SO4

(D) H3PO4

32. What is the pH of 20.0 mL of 0.050 M HCl?

(A) 1.30

(B) 1.70

(C) 2.60

(D) 3.00

33. Which is amphotheric (behaves either as an acid or as a base) in

aqueous solution?

(A) HClO3

(B) Ca(OCl)2

(C) NaOH

(D) Zn(OH)2

34. Which will yield the most acidic solution when 0.10 mol is mixed with 1

L of H2O?

(A) CaO

(B) Al2O3

(C) SiO2

(D) SO2

35. When a particular aqueous solution is diluted by a factor of ten with

H2O, the pH increases by one pH unit. This solution most likely contains a

(A) weak acid

(B) strong base

(C) strong acid

(D) buffer

36. Which species can act as both an oxidizing agent and a reducing agent?

(A) F2

(B) Cs

(C) ClO4¯

(D) SO32¯

37. Which is an oxidation-reduction reaction?

(A) Cu + 4 HNO3 ---> Cu(NO3)2 + 2 NO2 + 2 H2O

(B) AgNO3 + NaBr ---> AgBr + NaNO3

(C) Na2O + H2O ---> 2 NaOH

(D) NH3 + HF ---> NH4F

38. When this equation is balanced correctly, what is the coefficient for

I2?

__BrO3¯ + __I¯ + __H+ ---> __Br¯ + __I2 + __H2O

(A) 1

(B) 2

(C) 3

(D) 6

39. Which species contains the most neutrons?

(A) 26-Fe-59

(B) 29-Cu-61

(C) 30-Zn-61

(D) (30-Zn-60)2+

40. Which type of radiation changes both the atomic number and mass number

of the emiting atom?

(A) alpha

(B) beta

(C) gamma

(D) X-ray

41. Which group of elements is listed in order of increasing boiling point?

(A) lithium, sodium, potassium

(B) chlorine, bromine, iodine

(C) sulfur, chlorine, argon

(D) zinc, cadmium, mercury

42. The formula for the oxide of an element, X, is X2O3. Which is the most

likely formula for another compund of this element?

(A) XF6

(B) XH4

(C) X2Cl3

(D) X(NO3)3

43. Which element is the best electrical conductor?

(A) Al

(B) Si

(C) P

(D) Cl

44. Which is true about the relative sizes of these species?

(A) Na < Na+; F < F¯

(B) Na > Na+; F > F¯

(C) Na > Na+; F < F¯

(D) Na < Na+; F > F¯

45. Which atomic property generally increases down the periodic table but

decreases from left to right across it?

(A) ionization energy

(B) atomic number

(C) principal quantum number

(D) atomic radius

46. How many valence electrons are present in the C2O42¯ ion?

(A) 44

(B) 42

(C) 34

(D) 30

47. Which element combinations will form ionic compounds?

Element Combinations

I. Ca (Z = 20) and Ti (Z = 22)

II. Si (Z = 14) and Br (Z = 35)

III. Mg (Z = 12) and Cl (Z = 17)

(A) II only

(B) III only

(C) II and III

(D) I, II, and III

48. Which species is best represented by more than one Lewis structure

(that is, exhibits resonance)?

(A) NH4+

(B) O3

(C) CO

(D) SF4

49. Which molecule has the shortest bond length?

(A) N2

(B) O2

(C) F2

(D) Cl2

50. Which molecule will have the largest F-X-F bond angle?

(A) OF2

(B) NF3

(C) BF3

(D) CF4

51. Which piece of glassware should be used to measure 8.70 mL of a

solution?

(A) 20-mL graduated cylinder

(B) 25-mL volumetric flask

(C) 50-mL buret

(D) 100-mL beaker

52. During flame tests, which set of metal salts gives the colors red,

yellow, green and violet, respectively?

(A) Sr, Na, Ba, K

(B) Na, Ba, Sr, K

(C) Sr, K, Ba, Na

(D) K, NA, Ba, Sr

53. The density of an insoluble object is determined by weighing it on a

balance, then submerging it in a graduated cylinder to find its volume.

Based on the data collected, to how many significant figures should the

density be reported?

Density Data

mass 23.92 g

initial H2O volume 66 mL

final H2O volume 72 mL

(A) 1

(B) 2

(C) 3

(D) 4

54. When betitol, C6H12O4, is burned with excess oxygen to form carbon

dioxide and water, how many moles of oxygen are needed for each mole of

betitol?

(A) 1

(B) 6

(C) 7

(D) 9

55. A 2.70 g sample of an unknown hydrocarbon was burned in excess oxygen

to form 88.0 g of carbon dioxide and 27.0 g of water. What is a possible

molecular formula for the hydrocarbon?

(A) CH4

(B) C2H2

(C) C4H3

(D) C4H6

56. When 500.0 mL of 1.0 M LaCl3 and 3.0 M NaCl are mixed, what is the

molarity of the chloride ion?

(A) 4.0 M

(B) 3.0 M

(C) 2.0 M

(D) 1.5 M

57. How is each property affected when a nonvolatile solute is added to a

pure solvent?

Vapor pressure freezing point boiling point

(A) increases increases increases

(B) increases decreases increases

(C) decreases decreases decreases

(D) decreases decreases increases

58. How many joules are required to raise the temperature of 35.0 mL of

liquid mercury from 25 °C to 38 °C?

Properties of liquid mercury

Specific heat 0.139 J g¯1 °C¯1

Density 13.6 g mL¯1

(A) 6.6 x 101

(B) 2.5 x 102

(C) 8.6 x 102

(D) 6.2 x 103

59. The reaction between gaseous ammonia and oxygen is given by the

equation:

4 NH3(g) + 7 O2(g) ---> 4 NO2(g) + 6 H2O(l)

DH = -1397.8 kJ

What is the standard enthalpy of formation of NH3(g) [in kJ mol¯1], given

these standard enthalpies of formation?

Standard Enthalpies of Formation

NO2(g) 33.18 kJ mol¯1

H2O(l) -285.18 kJ mol¯1

(A) -45.1

(B) -63.1

(C) -184.4

(D) -252.6

60. The reaction: 2 ICl + H2 ---> 2 HCl + I2 has been proposed to occur by

this mechanism:

H2 + ICl --- HCl + HI (slow)

HI + ICl --- HCl + I2 (fast)

Which rate law best agrees with this information?

(A) Rate = k [H2]

(B) Rate = k [ICl]2

(C) Rate = k [H2] [ICl]2

(D) Rate = k [H2] [ICl]

61. Which gas had an average molecular velocity that is 4 times as great as

that of sulfur dioxide?

The Molar Mass of SO2 is 64 g mol¯1

(A) H2 (M = 2 g mol¯1)

(B) He (M = 4 g mol¯1)

(C) CH4 (M = 16 g mol¯1)

(D) O2 (M = 32 g mol¯1)

62. For the reaction;

2 NO(g) + O2(g) <===> 2 NO2(g)

the equilibrium concentrations at a certain temperature are found to be

[NO] = 0.10 M, [O2] = 0.20 M, [NO2] = 0.30 M. The value of the equilibrium

constant for this reaction at this temperature is

(A) 1.5

(B) 15

(C) 45

(D) 150

63. A solution of Na2CO3 is added slowly to a solution initially containing

equal concentrations of Ba2+, Cd2+, Fe2+, and Zn2+ ions. Which compound

will precipitate first?

Solubility Product Constant

BaCO3 2.6 x 10¯9

FeCO3 3 x 10¯11

CdCO3 6 x 10¯12

ZnCO3 1 x 10¯10

(A) BaCO3

(B) FeCO3

(C) CdCO3

(D) ZnCO3

64. According to the equations;

H2CO3 + H2O <===> H3O+ + HCO3¯

HCO3¯ + H2O <===> H3O+ + CO32¯

what is the conjugate base of HCO3-?

(A) H2CO3

(B) CO32¯

(C) H2O

(D) H3O+

65. What is the [OH¯] in the final solution prepared by mixing 20.0 mL of

0.050 M HCl with 30.0 mL of 0.10 M of Ba(OH)2?

(A) 0.12 M

(B) 0.10 M

(C) 0.40 M

(D) 0.0050 M

66. What voltage will be produced by the electrochemical cell?

Reduction Potentials

Pb2+ + 2 e¯ ---> Pb -0.13 V

Al3+ + 3 e¯ ---> Al -1.68 V

(A) 2.97V

(B) 1.55V

(C) -1.81V

(D) -2.97V

67. How many grams of cobalt metal will be deposited when a solution of

cobalt(II) chloride is electrolyzed with a current of 10. amperes for 109

minutes?

(A) 0.66

(B) 4.0

(C) 20

(D) 40

68. Which element will have the greatest number of unpaired electrons?

(A) Co (Z = 27)

(B) Ni (Z = 28)

(C) Cu (Z = 29)

(D) Ga (Z = 31)

69. What is the hybridization of the carbon that is bonded to the nitrogen?

(A) sp

(B) sp2

(C) sp3

(D) dsp3

70. Which molecule is polar?

(A) CO2

(B) NH3

(C) SiCl4

(D) PF5

Answers

The answers to this test is not available on the internet.Try to solve

these questions on your own.

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------------------------------

chemistry:1992(local test)

1. Which represents the 235U atom?

Protons Electrons Neutrons

(A) 46 46 143

(B) 92 92 92

(C) 92 92 143

(D) 92 92 146

2. One mole of an element contains 4.82 x 1024 electrons. What is the

atomic number of the element?

(A) 2

(B) 4

(C) 6

(D) 8

3. How many H atoms are contained in 1.50 g of glucose (C6H12O6)?

(A) 3.01 x 1022

(B) 1.20 x 1023

(C) 2.40 x 1023

(D) 6.02 x 1022

4. Which contains the greatest mass of chlorine?

(A) 5.0 g Cl2

(B) 30.0 g MgCl2

(C) 0.50 mol Cl2

(D) 0.90 mol KCl

5. A particular chlorofluorocarbon (CFC) contains 9.93% C, 31.43% F, and

58.64% Cl by mass. Its molar mass is 120.9 g/mol. How many F atoms are in

one molecule?

(A) 1

(B) 2

(C) 3

(D) 4

6. On heating, Cl2O7 decomposes to form Cl2 and O2. What is the ratio of

chlorine to oxygen molecules in the product?

(A) 2 to 7

(B) 2 to 14

(C) 3 to 7

(D) 4 to 7

7. What is the coefficient for Fe2+ when the redox equation is

Fe2+ + MnO4¯ + H+ ---> Fe3+ + Mn2+ + H2O

is balanced when using the smallest whole-number coefficients?

(A) 2

(B) 3

(C) 4

(D) 5

8. Hydrogen peroxide, H2O2, in the presence of a catalyst decomposes into

water and oxygen gas. How many mL of O2 at STP are produced from the

decomposition of 5.0 g of H2O2?

(A) 230 mL

(B) 460 mL

(C) 870 mL

(D) 1650 mL

9. Which statement pertains to the measured pressure of gas collected when

O2 is collected over water?

(A) It is greater than the pressure of dry O2

(B) It is less than the pressure of dry O2

(C) It is equal to the pressure of dry O2

(D) It varies inversely with the pressure of dry O2

10. Which observation is an exception to the behavior predicted by kinetic

molecular theory?

(A) When propane gas is subjected to a high enough pressure, it

liquifies.

(B) When an inflated balloon is placed in liquid nitrogen, it flattens,

but regains its shape when returned to room temperature.

(C) Tire pressure readings are higher when tires are hot after a long

trip.

(D) When the button on a spray can is pushed, the material inside flows

out of the can.

11. A gas has a density of 4.36 g L¯1 at 20 °C and a pressure of 1.25 atm.

Which noble gas best fits these data?

(A) Ne

(B) Ar

(C) Kr

(D) Xe

12. A gas is likely to behave in a non-ideal fashion in all of the

situations given except

(A) At very low temperatures, because the particles have insufficient

kinetic energy to overcome intermolecular attractions.

(B) in mixtures of gases where the molecules are polar, because

intermolecular forces are more likely.

(C) at standard temperature and pressure, because intermolecular

interations are minimized.

(D) at very high pressures, because the distance between molecules is

likely to be small in relation to molecular diameter.

13. A sample of gas originally occupies 2.56 L at a temperature of 25 °C

and a pressure of 686 mmHg. The temperature is increased to 35 °C and the

pressure is reduced to 461 mmHg. What is the final volume of gas?

(A) 3.94 L

(B) 3.69 L

(C) 1.78 L

(D) 1.66 L

14. Brass is an alloy composed of

(A) copper and tin.

(B) copper and zinc.

(C) copper and lead.

(D) zinc and tin.

15. When Na2O2 dissolves with water, what are the end products?

(A) NaOH(aq) and H2(g)

(B) NaOH(aq) and O2(g)

(C) NaH(s) and O2(g)

(D) Na2O(s) and O2(g)

16. The properties of the elements are periodic functions of their

(A) atomic number.

(B) atomic volume

(C) atomic mass

(D) atomic density.

17. The compounds of what element found in fossil fuels are major

contributors to acid rain?

(A) phosphorus

(B) carbon

(C) sulfur

(D) nitrogen

18. Which list of elements are arranged in order of increasing atomic size

(largest last)?

(A) Li, Na , K, Rb

(B) Rb, K Na, Li

(C) Li, Na, Rb, K

(D) Li, K, Na, Rb

19. What is the ground state electronic configuration for the Cu atom?

(A) 1s2 2s2 2p2 3s2 3p6 3d9 4s2

(B) 1s2 2s2 2p6 3s2 3p2 3p6 3d10 4s1

(C) 1s2 2s2 2p6 3s2 3p6 3d8 4s3

(D) 1s2 2s2 2p6 3s2 3p6 3d9 4s1 4p1

20. Which atom has two unpaired electrons and is therefore paramagnetic?

(A) He

(B) Be

(C) B

(D) C

21. What is the ground state electron configuration for the Ba2+ ion?

(A) [Xe] 6s1

(B) [Xe] 6s2

(C) [Xe]

(D) [Kr] 4d10 5s2 5p4

22. Which sequence is arranged in order of increasing ionization energies?

(A) Be, B, C, N, O

(B) B, Be, C, O, N

(C) Be, B, C,O, N

(D) B, Be, C, N, O

23. When solid iodine sublimes, what are the chemical forces that must be

overcome?

(A) intramolecular covalent bonds

(B) hydrogen bonds

(C) dispersion forces

(D) dipole forces

24. Carbon and silicon are in the same chemical family. Which is true for

both elements?

(A) Each shows a strong ability to bond to itself in compounds.

(B) Both commonly form multiple bonds by overlap of p atomic orbitals.

(C) In pure form, both often form tetrahedron shaped structures.

(D) All of the above.

25. Which type solid, as a class, generally has a low melting point?

(A) molecular solid

(B) ionic solid

(C) hydrogen bonded solid

(D) metallic solid

26. For which molecule are resonance structures necessary to describe the

bonding satisfactorily?

(A) H2S

(B) SO2

(C) CO2

(D) OF2

27. Which color for flame tests is not correct?

(A) Sodium, yellow

(B) Potassium, violet

(C) lithium, green

(D) all are correct

28. What is the shape and polarity of the PF3 molecule?

(A) trigonal pyramidal, polar

(B) trigonal pyramidal, nonpolar

(C) trigonal planar, polar

(D) trigonal planar, nonplolar

29. When 50.0 mL of 0.200 M HCl is mixed with 150.0 mL of 0.100 M NaOH, the

reaction is as shown.

NaOH(aq) + HCl(aq) ---> NaCl(aq) + H2O(l)

What is the concentration of the resulting solution?

(A) 0.0500 M NaCl

(B) 0.100 M NaCl

(C) 0.0500 M NaCl and 0.0250 M NaOH

(D) 0.0500 M NaCl and 0.0500 M NaOH

30. Refer to the heating curve to the right for 50.0 g of a compound with a

molar mass of 94.1 g. What is the melting point of the compound?

(A) 25

(B) 55

(C) 75

(D) 95

31. Which would you expect to be the strongest acid?

(A) HBrO3

(B) HIO3

(C) HClO3

(D) all should be equally strong.

32. The solubility of which salt is not pH dependent?

(A) CaF2

(B) CaCO3

(C) CaC2O4

(D) CaCl2

33. Consider a reaction 2 A(s) + B(g) <===> 2 C(g). If 0.20 mol A, 0.30 mol

B and 0.10 mol C are present in a 1. 0 L flask at equilibrium, what is Kc?

(A) 0.033

(B) 0.83

(C) 1.67

(D) 30.3

34. Which effect will not increase the amount of CO(g) present at

equilibrium? The reaction is endothermic.

CO2(g) + H2(g) <===> CO(g) + H2O(g)

(A) Decrease the concentration of H2O(g).

(B) Increase the concentration of H2(g).

(C) Increase the volume of the container.

(D) Increase the temperature of the container.

35. Which 0.500 M solution has the lowest pH?

(A) HC2H3O2 (Ka = 1.8 x 10¯5)

(B) NaCN (Kb = 2.5 x 10¯5)

(C) NH3 (Kb = 1.8 x 10¯5)

(D) HN3 (Ka = 2.0 x 10¯5)

36. 0.2 M hypochlorous acid (pKa = 7.51) is titrated with 0.2 M sodium

hydroxide solution. Which indicator of those with ranges listed would be

most appropriate for marking the endpoint of this titration?

(A) methyl orange pH = 3.2-4.4

(B) bromocresol purple pH = 5.2-6.8

(C) cresol red pH = 7.0-8.8

(D) alizarin yellow pH = 10.1-12.0

37. Which oxide is the most acidic?

(A) MgO

(B) CO2

(C) SO2

(D) SO3

38. Which set of quantum numbers represents a 2p electron?

n l m s

(A) 1 0 0 1/2

(B) 2 1 1 1/2

(C) 2 2 -1 -1/2

(D) 4 3 -1 -1/2

39. Which is not true for the transition metal elements?

(A) Most have multiple oxidation states.

(B) Most of their compounds are gaseous.

(C) Many of their compounds are colored.

(D) Many form strong complex ions.

40. Which coupound is most likely to form intermolecular hydrogen bonds?

(A) C3H8

(B) CaH2

(C) C3H7OH

(D) CH3SH

41. An aqueous solution of which salt would be expected to have the most

basic pH?

(A) Na2CO3

(B) NaC2H3O2

(C) NaCl

(D) NH4Cl

42. What is the approximate pH of an aqueous 1 x 10¯9 M HCl solution?

(A) 1

(B) 5

(C) 7

(D) 9

Use the titration curve below to answer questions 43-45.

43. Which point indicates the region where the solution behaves as a

buffer?

(A) A

(B) B

(C) C

(D) D

44. Which point indicates the equivalence point of the titration?

(A) E

(B) B

(C) C

(D) D

45. The titration curve best describes a titration between

(A) a strong acid and a strong base.

(B) a strong acid and weak base.

(C) a weak acid and a strong base

(D) a weak acid and a weak base.

46. Which molecule has the shortest bond length?

(A) N2

(B) O2

(C) Cl2

(D) Br2

47. An exothermic equilibrium reaction will

(A) go faster with a larger Keq at higher temperatures.

(B) go faster with a smaller Keq at higher temperatures.

(C) go slower with a larger Keq at higher temperatures.

(D) go slower with a smaller Keq at higher temperatures.

48. Consider the endothermic equilibrium reaction of BaCO3(s) <===> BaO(s)

+ CO2(g). Which would produce more BaO(s)?

(A) Decreasing the temperature.

(B) Decreasing the pressure.

(C) Adding more CO2(g).

(D) All of the above would shift the equilibrium left.

49. If the coefficients of all species in a chemical reaction are divided

in half, the reaction is still balanced. The new reaction would have an

equilibrium constant with a value that is _______ the value for the first

reaction.

(A) the same as

(B) twice

(C) half

(D) the square root of

50. Which crystal packing of atoms results in proportionately less

unoccupied volume per unit cell?

(A) simple cubic

(B) body centered cubic

(C) face centered cubic

(D) The unoccupied volume is constant for all.

PART II

51. In the series HF, HCl, HBr, HI, the last three compounds demonstrate

increasing normal boiling points with increasing molar mass, but HF

possesses an unusually high boiling point, as noted in the table below.

What is the reason for HF's unusual behavior?

Hydrogen halide Boilng point

HF +120 °C

HCl -84.9 °C

HBr -67.0 °C

HI -50.8 °C

(A) dipole-dipole forces

(B) London forces

(C) hydrogen bonding

(D) instantaneous dipole-dipole forces

52. Consider two solutions: a 0.50 m solution of Ca(NO3)2 and a 0.75 m

solution of KCl. Which statement about the solutions is correct?

(A) The potassium chloride solution has a lower freezing point because

the salt concentration is greater.

(B) The calcium nitrate solution has a higher freezing point because

the total ion concentration is greater.

(C) Both solutions freeze at the same temperature, which is lower than

0 °C, because they have equal ion concentrations.

(D) both solutions freeze at 0 °C because the concentration of solute

is too small to cause any variation in freezing point.

53. A 0.73 mol sample of a salt of sodium is dissolved in 150 g of pure

water. The boiling point of the solution is 105 °C. The most likely anion

in this solution is : (Kb = 0.512 °C m¯1).

(A) nitrate

(B) sulfate

(C) phosphate

(D) none of these

54. Which is a base under the Arrhenius, Bronsted-Lowry and Lewis theories?

(A) NH3

(B) OH¯

(C) O2¯

(D) H2O

55. A saturated solution of Mg(OH)2 has a molar solubility of 1.44 x 10¯4

M. What is its solubility product constant, Ksp?

(A) 1.2 x 10¯11

(B) 2.1 x 10¯8

(C) 3.0 x 10¯12

(D) 4.2 x 10¯8

56. The Ksp for Fe(IO3)3 is 1.0 x 10¯14. A solution containing Fe3+ is

mixed with a solution containing IO3¯, and at the instant of mixing, [Fe3+]

= 10¯4 M and [IO3¯] = 10¯5 M. Which statement is accurate?

(A) A precipitate forms, because Qsp > Ksp.

(B) A precipitate forms, because Qsp < Ksp.

(C) No preciptate forms, because Qsp > Ksp.

(D) No precipitate forms, because Qsp < Ksp.

57. Which equation represents the standard heat of formation reaction for

P4O10(s)?

(A) 2 P2(g) + 5 O2(g) ---> P4O10(s)

(B) 2 P2(s) + 5 O2(g) ---> P4O10(s)

(C) P4(g) + 5 O2(g) ---> P4O10(s)

(D) P4(s) + 5 O2(g) ---> P4O10(s)

58. Corrosion of ships can be minimized by attaching a "sacrificial plate"

of zinc to the hull. This plate corrodes instead of the steel of the ship

because

(A) the zinc behaves as a cathode, and is oxidized to zinc ions.

(B) the zinc behaves as an anode, and is oxidized to zinc ions.

(C) the steel hull behaves as a cathode, and is reduced to iron ions.

(D) the steel hull behaves as an anode, and is reduced to iron ions.

59. A spoon is made the cathode in an electroplating apparatus containing a

AgNO3 solution. How many grams of Ag will be plated on the spoon if a

current of 2.00 A is passed through the apparatus for 1.90 min.?

(A) 0.255 g

(B) 0.150 g

(C) 0.128 g

(D) 0.0638 g

60. A cell is set up using the following reactions:

Zn | Zn2+ (0.5M) || Ni2+ (0.1 M) | Ni

Ni2+ + 2e¯ ----> Ni E° = -0.250 V

Zn2+ + 2e¯ ----> Zn E° = -0.763 V

What is the voltage of the cell?

(A) -0.513 V

(B) -1.013 V

(C) 0.492 V

(D) 0.513 V

61. Given the thermochemical equations

2 Cu2O(s) + O2(g) ---> 4 CuO(s) DH° = -287.9 kJ

Cu2O(s) ---> CuO(s) + Cu(s) DH° = 11.3 kJ

What is the standard heat of formation of CuO(s)?

(A) 132.7 mol¯1

(B) -132.7 mol¯1

(C) 155.3 kJ mol¯1

(D) -155.3 kJ mol¯1

62. What is the amount of heat that is released when 8.17 g of Al(s) are

converted to Al2O3 (s) at 25 °C and 1 atm via the reaction shown?

4 Al(s) + 3 O2(g) ---> 2 Al2O3(s)

for this reaction, DH° = -3352 kJ

(A) 134 kJ

(B) 254 kJ

(C) 268 kJ

(D) 1.01 x 103 kJ

63. What are the signs of the enthalpy and entropy for the vaporizaton of

benzene?

C6H6(l) ---> C6H6(g)

DH° DS°

(A) + +

(B) + -

(C) - +

(D) - -

64. The slowest step of a reaction is called the

(A) elementary process

(B) molecularity.

(C) order.

(D) rate-determining step.

65. For a first- order reaction of half-life 150 min, what is the rate

constant in min¯1? t1/2 = 0.693 / k1

(A) 0.00104

(B) 0.00462

(C) 69.3

(D) 216

66. What is the reducing agent in the forward reaction?

H2O2(aq) + 2 HI(aq) ---> 2 H2O(l) + I2(s)

(A) H2O2

(B) HI

(C) H2O

(D) I2

67. What is the hydridization of the central carbon in the compound

H2C=C=CH2?

(A) sp

(B) sp2

(C) sp3

(D) sp3d

68. What condition describes a reaction at equilibrium?

(A) DG = 0

(B) DG° = 0

(C) DG° = DG°

(D) ln K = 0

69. What is the wavelength of green light that has a frequency of 5.2 x

1014 Hz?

(A) 155 nm

(B) 173 nm

(C) 347 nm

(D) 577 nm

70. The addition of which solution would provide the best way to

distinguish between AgNO3(aq) and Zn(NO3)2(aq)?

(A) H2O

(B) HNO3

(C) NH3

(D) HCl

Answers

# Ans. # Ans. # Ans.

1. C 25. A 49. D

2. D 26. B 50. C

3. D 27. C 51. C

4. C 28. A 52. C

5. B 29. C 53. A

6. A 30. B 54. B

7. D 31. C 55. A

8. D 32. D 56. D

9. A 33. B 57. D

10. A 34. C 58. B

11. C 35. D 59. A

12. C 36. D 60. C

13. A 37. D 61. D

14. B 38. B 62. B

15. B 39. B 63. A

16. A 40. C 64. D

17. C 41. A 65. B

18. A 42. C 66. B

19. B 43. C 67. A

20. D 44. D 68. A

21. C 45. C 69. D

22. B 46. A 70. D

23. C 47. B

24. D 48. B

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chemistry :1991

1. What is the maximum amount of MgCl2 that can be prepared from the

reaction of 10.0g of HCl with 10.0 of Mg(OH)2 ?

2 HCl + Mg(OH)2 ---> MgCl2 + 2 H2O

(A) 9.26 g

(B) 13.1 g

(C) 16.3 g

(D) 17.5 g

2. Phenylflouroform contains 57.54% C, 3.45% H, and 39.01% F. Its molecular

formula is the same as its simplest formula. How many carbon atoms are in

one molecule of Phenyflouroform ?

(A) 4

(B) 5

(C) 6

(D) 7

3. What is the most likely formula for a compound of gallium and sulfur ?

(A) GaS

(B) GaS2

(C) Ga2S3

(D) Ga3S2

4. A mixture of 2.30 x 1023 molecules N2 and 4.35 x 1023 molecules N2O has

a total pressure of 2.00 atm. What is the partial pressure of N2 ?

(A) 0.346 atm

(B) 0.654 atm

(C) 0.692 atm

(D) 1.11 atm

5. Which element should have the smallest first ionization energy ?

(A) Ca

(B) Rb

(C) Al

(D) Cl

6. An aqueous solution containing 1.00 mol H2SO4 is mixed with an aqueous

solution containing 1.00 mol NaOH. The mixture is then evaporated to

dryness. What solid remains after evaporation ?

(A) H2SO4

(B) NaOH

(C) NaHSO4

(D) Na2SO4

7. Which atom is the smallest ?

(A) Rb

(B) Ag

(C) Sb

(D) I

8. At room temperature and 1 atm pressure the molecules are farthest apart

in

(A) flourine

(B) bromine

(C) iodine

(D) water

9. What is the net-ionic equation for the reaction of aqueous solutions of

BaCl2 and K2SO4?

(A) Ba2+(aq) + 2Cl¯(aq) + 2K+(aq) + SO42¯(aq) ---> BaSO4(s) + 2K+(aq) +

2Cl¯(aq)

(B) Ba2+(aq) + SO42¯(aq) ---> BaSO4(s)

(C) K+(aq) + Cl¯(aq) ---> KCl(s)

(D) Ba2+(aq) + 2Cl¯(aq) + 2K+(aq) + SO42¯(aq) ---> BaSO4(s) + 2KCl(s)

10. When 80.00 mL of 0.200 M HNO3 is added to 120.00 mL of 0.150 M KOH, the

reaction

HNO3(aq) + KOH(aq) ---> KNO3(aq) + H2O(l)

occurs and the resulting solution is

(A) 0.0160 M KNO3

(B) 0.0180 M KNO3

(C) 0.0800 M KNO3 and 0.0100 M KOH

(D) 0.0160 M KNO3 and 0.0200 M KOH

11. Methanol burns in oxygen according to the equation

CH3OH + O2 ---> CO2 + H2O (unbalanced)

What volume of oxygen is required to burn 5.0 L of gaseous methonal

measured at the same temperature and pressure ?

(A) 15.0 L

(B) 3.3 L

(C) 7.5 L

(D) 5.0 L

12. A 50 g sample of an ideal gas occupies a volume of 3.2 L at 40 °C and

exerts a pressure of 2.6 atm. What is its molar mass ?

(A) 150 g mol¯1

(B) 2.0 g mol¯1

(C) 77 g mol¯1

(D) 310 g mol¯1

13. When sodium metal reacts with an excess of water the products are

(A) Na2O(s) and H2(g)

(B) Na+(aq), OH¯(aq) and H2(g)

(C) NaH(s) and O2(g)

(D) Na2O2(s) and H2(g)

14. Which is least important in determining the physical behavior of a gas?

(A) volume

(B) pressure

(C) temperature

(D) chemical composition

15. Which pair of atoms should form the most polar bond ?

(A) B and F

(B) C and O

(C) O and F

(D) F and N

16. Which pair of ions should form the strongest ionic bond?

(A) Li+ and I¯

(B) Na+ and F¯

(C) Cs+ and F¯

(D) Na+ and O2¯

17. The kinetic-molecular theory predicts that two gases at the same

temperature will have the same

(A) average speed

(B) average kinetic energy

(C) pressure

(D) rate of effusion

18. Which factors do not affect the vapor pressure of a liquid at

equilibrium?

I. Intermolecular forces of attraction.

II. The volume of liquid present.

III. The temperature of the liquid

(A) I only

(B) II only

(C) I and II only

(D) II and III only

19. Which has the highest vapor pressure at room temperature ?

(A) a vegetable oil

(B) gasoline

(C) table sugar, C12H22O11

(D) table salt, NaCl

20. Identify the best Lewis structure for hydrogen cyanide.

21. Which oxide of chlorine exhibits the maximum oxidation state that

really exists for chlorine?

(A) ClO

(B) ClO4

(C) Cl2O5

(D) Cl2O7

22. Which has the largest radius ?

(A) Na

(B) Na+

(C) F¯

(D) Ne

23. What is the molarity of HCl if 450 mL of 2.3 M HCl is diluted to 1250

mL ?

(A) 0.36 M

(B) 0.50 M

(C) 0.83 M

(D) 1.8 M

24. The first five ionization energies in kJ mol¯1, for a particular

element are shown.

1st 2nd 3rd 4th 5th

580 1815 2740 11,600 18,500

The element is likely to form a ionic compounds in which its charge is

(A) 1+

(B) 2+

(C) 3+

(D) 4+

25. Which compound, when dissolved in water, conducts electricity and forms

a basic solution ?

(A) HCl

(B) CH3COOH

(C) CH3OH

(D) KOH

26. Which pair constitutes a buffer ?

(A) HCl and KCl

(B) NaOH and NaCl

(C) HNO2 and NaNO2

(D) HNO3 and NH4NO3

27. Which oxide dissolves in water to give the strongest acid ?

(A) SO3

(B) CaO

(C) P4O10

(D) CO2

28. Which is the strongest Bronsted base ?

(A) NH2¯

(B) Cl¯

(C) PO43¯

(D) NO2¯

29. In the reaction F¯ + H2O ---> HF + OH¯ an acid-base conjugate pair is

(A) F¯ and H2O

(B) F¯ and OH¯

(C) H2O and HF

(D) F¯ and HF

30. Which is the anhydride of nitric acid ?

(A) NO

(B) NO2

(C) N2O3

(D) N2O5

31. Which forms a basic aqeous solution ?

(A) NaI

(B) KNO3

(C) BaCl2

(D) Na2CO3

32. The best acid for preparing a buffer of pH = 3.2 has a Ka near

(A) 2.0 x 10¯5

(B) 6.0 x 10¯4

(C) 3.2 x 10¯2

(D) 4.0 x 10¯6

33. What is the pH of a 2.0 x 10¯3 M HCl solution ?

(A) 2.40

(B) 2.70

(C) 3.00

(D) 11.30

34. Consider a solution that contains only one ion, Ag+, Pb2+, or Hg22+.

The solution gave a precipitate with HCl that was insoluble in hot water

but was soluble in dilute ammonia solution. Which ion was present ?

(A) Pb2+

(B) Ag+

(C) Hg22+

(D) The information is insufficient to identify the ion

35. What is the partial pressure of CO2(g) if Kp for the reaction is 1.04

atm ?

CaCO3(s) <===> CaO(s) + CO2(g)

(A) 0.52 atm

(B) 1.04 atm

(C) 1.08 atm

(D) 10.4 atm

36. The Ksp values for CaSO4,BaSO4, and Ag2SO4 are 2.0 x 10¯4, 1.5 x 10¯9,

and 1.5 x 10¯5 respectively. If 0.010 M Na2SO4 is slowly added to a

solution that contains Ca2+, Ba2+, and Ag+ (each 0.10M), which solid will

precipitate last?

(A) CaSO4

(B) Ag2SO4

(C) BaSO4

(D) More information is required

37. The Ksp of AgCl is 1.8 x 10¯10. If 10.00 mL of 0.0010 M NaCl is

combined with 20.00 mL of 0.0050 M AgNO3

(A) no reaction occurs

(B) a precipitate forms

(C) an initial precipitate forms which dissolves upon stirring.

(D) the silver ion concentration remainsas 0.005 M.

38. N2(g) + 3H2(g) <===> 2NH3(g) + 92.2 kJ

The partial pressure of N2 is not increased by

(A) decreasing container size

(B) adding NH3

(C) increasing temperature

(D) removing H2

39. Which value for an equilibrium constant, K, could indicate that the

reaction

A(g) + B(g) ---> C(g)

goes nearly to completion?

(A) 1014

(B) 10¯14

(C) 1

(D) 0

40. Which is most soluble in a polar solvent?

(A) CF4

(B) Br2

(C) HCl

(D) BCl3

41. When a liquid is placed in a closed container

(A) evaporation stops

(B) evaporation continues for a time then stops

(C) the vapor pressure above the liquid becomes one atmosphere

(D) evaporation and condensation continue to occur, but at equal rates

42. The sublimination of dry ice is an endothermic process. The energy

absorbed is required to overcome

(A) covalent bonds

(B) polar covalent bonds

(C) dipole forces

(D) dispersion forces

43. Compared to a 1.0 M aqueous solution of a nonelectrolyte, a 1.0 M

solution of an electrolyte will have a

(A) higher melting point and higher boiling point

(B) higher melting point and lower boiling point

(C) lower melting point and lower boiling point

(D) lower melting point and higher boiling point

44. Which is planar?

(A) H3O+

(B) PCl3

(C) CO32¯

(D) NH4+

45. Calculate DH°f for

4 NH3(g) + 3 O2(g) ---> 2 N2(g) + 6 H2O(g)

Given that DH°f for NH3(g) and H2O(g) are -46.0 and -242 kJ mol¯1

respectively.

(A) -1268 kJ

(B) -196 kJ

(C) +1268 kJ

(D) +196 kJ

46. A white, odorless, crystalline solid melts after about ten seconds in a

burner flame. It is soluble in water and insoluble in carbon tetrachloride.

Neither the melt nor its aqueous solution conducts electricity. We conclude

that the substance is

(A) an ionic compound

(B) a non-polar covalent compound

(C) a polar covalent compound

(D) a pure element

47. Given the standard reduction potentials,

Cr3+ + 3e¯ ---> Cr -0.74 V

Pb2+ + 2e¯ ---> Pb -0.13 V

what is the standard potential, E°, for the following reaction?

2 Cr + 3 Pb2+ ---> 2 Cr3+ + 3 Pb

(A) 0.61 V

(B) 0.87 V

(C) 1.09 V

(D) 1.87 V

48. A mixture of 0.10 mol H2 and 0.050 mol O2 are placed in a bomb

calorimeter with a heat capacity of 5.1 x 104 J °C¯1. The initial

temperature is 25.00 °C and the temperature after combustion is 25.56 °C.

What is the DH°f for H2O(l)? (Assume 100% conversion to water.)

(A) -286 kJ mol¯1

(B) +190 kJ mol¯1

(C) -190 kJ mol¯1

(D) +286 kJ mol¯1

49. In the reaction

2MnO4¯ + 16H+ + 10Br¯ ---> 2Mn2+ + 8H2O + 5Br2

Br¯ ion is the

(A) oxidizing agent and is oxidized

(B) oxidizing agent and is reduced

(C) reducing agent and is oxidized

(D) reducing agent and is reduced

50. For BrF3, the orbital geometry of the central atom and the molecular

geometry are, respectively,

(A) trigonal planar and trigonal planar

(B) trigonal planar and trigonal bipyramidal

(C) trigonal bipyramidal and trigonal planar

(D) trigonal bipyramidal and T-shaped

51. How many electrons are needed to convert one nitrate ion into one

ammonia molecule?

(A) 3

(B) 5

(C) 6

(D) 8

52. Which species below violates the octet rule?

(A) CF4

(B) BF3

(C) N2O

(D) NO3¯

53. What is the coefficient for H2O when the redox equation

Cu + NO3¯ + H+ ---> Cu2+ + NO + H2O

is balanced using smallest whole - number coefficients?

(A) 1

(B) 2

(C) 3

(D) 4

54. Which change will produce an increase in the entropy of a system?

(A) decreasing the temperature

(B) forming a precipitate in a solution

(C) decreasing the volume

(D) forming a gas from a solid reaction

55. Which will cause the value of the equilibrium constant for this

reaction to increase?

2A(g) + B(g) ---> C(g); DH° = 280 kJ

(A) adding a catalyst

(B) increasing the concentration of A

(C) increasing the concentration of C

(D) increasing the temperature

56. Given

2CO(g) + O2(g) ---> 2CO2(g); DG° = -516 kJ

4MnO(s) + O2(g) ---> 2Mn2O3(s); DG° = -312 kJ

Calculate the value of DG° for

2MnO(s) + CO2(g) ---> Mn2O3(s) + CO(g)

(A) +102 kJ

(B) -102 kJ

(C) +204 kJ

(D) -204 kJ

57. Given

Br2(l) S° = 152.2 J mol¯1 K¯1 and DH°f = 0 kJ mol¯1

Br2(g) S° = 245.4 J mol¯1 K¯1 and DH°f = 30.9 kJ mol¯1

Calculate the boiling point of liquid bromine.

(A) 58.4 K

(B) 332 K

(C) 125 K

(D) -147 K

58. Which is not expected to have a value of zero?

(A) DH°f for Cl2(g)

(B) DG°f for Na(s)

(C) S° for Ca(s)

(D) DH°f for Al(s)

59. The half-life of 14C is 5570 years. How many years will it take for 90%

of a sample to decompose?

(A) 5,570 years

(B) 17,700 years

(C) 18,600 years

(D) 50,100 years

60. A solution containg 2.10 g of Fe(NH4)2(SO4)2 . 6 H2O (M = 392.1 g

mol¯1) was titrated with acidic Na2Cr2O7 solution, requiring 41.60 mL of

Na2Cr2O7 solution. What is the molarity of Na2Cr2O7?

6 Fe2+ + Cr2O72¯ + 14 H+ ---> 6 Fe3+ + 2 Cr3+ + 7 H2O

(A) 0.0215 M

(B) 0.0387 M

(C) 0.0644 M

(D) 0.0744 M

61. What is the approximate H-O-H bond angle in H3O+?

(A) 60

(B) 90

(C) 109

(D) 120

62. What hybrid orbitals are used by nitrogen in N2F2?

(A) sp

(B) sp2

(C) sp3

(D) p only

63. The strongest interaction between atoms listed below is

(A) an instantaneous dipole-dipole interaction

(B) a dipole-dipole interaction

(C) a hydrogen bond

(D) a covalent bond

64. When a 5.0 g sample of an unknown compound is dissolved in 250.0 g of

benzene, the freezing point of benzene decreased 1.4 °C. The freezing point

depression constant, Kf, for benzene is 5.12 °C m¯1. What is the

approximate molar mass of the compound?

(A) 290 g mol¯1

(B) 73 g mol¯1

(C) 36 g mol¯1

(D) 140 g mol¯1

65.

Half-cell reaction Standard reduction potential, E°

Cu2+ (aq) + 2e¯ ---> Cu(s) -0.25 V

Ni2+ (aq) + 2e¯ ---> Ni(s) +0.34 V

When two half-cells are connected using a salt bridge,

(A) a galvanic cell will result in which Cu is the cathode

(B) a galvanic cell will result in which Cu is the anode

(C) an electrolytic cell will result in which Ni is the anode

(D) an electrolytic cell will result in which Ni is the anode

66. What is the maximum number of electrons that can occupy the 5d

subshell?

(A) 2

(B) 6

(C) 10

(D) 14

67. For the isoelectronic series below, which species requires the least

energy to remove an outer electron?

(A) K+

(B) Ar

(C) Cl¯

(D) S2¯

68. In aqueous solution, iodide ion (in basic solution) is oxidized by

hypochlorite ion:

OCl¯(aq) + I¯(aq) ---> OI¯(aq) + Cl¯(aq)

The rate of formation of hypoiodite, OI¯, is given by the rate law

rate = ( k [OCl¯] [I¯] ) / [OH¯]

What is the overall reaction order for the formation of OI¯?

(A) 1

(B) 2

(C) 3

(D) 4

69. The dissociation of HI molecules, as shown below, occurs at a

temperature of 629 K. The rate constant, k = 3.02 x 10¯5 M¯1 s¯1.

2 HI(g) ---> H2(g) + I2(g)

What is the reaction order?

(A) 0

(B) 1

(C) 2

(D) 3

70. A sodium vapor street lamp emits yellow light with a wavelength of 589

nm. What is the energy of this light per mole of protons?

(A) 3.37 x 10¯16 kJ mol¯1

(B) 2.35 x 10¯13 kJ mol¯1

(C) 0.201 kJ mol¯1

(D) 203 kJ mol¯

Answers

1. B 21. D 41. D 61. C

2. D 22. D 42. D 62. B

3. C 23. C 43. D 63. D

4. C 24. C 44. C 64. B

5. B 25. D 45. A 65. B

6. C 26. C 46. C 66. C

7. D 27. A 47. A 67. D

8. A 28. A 48. A 68. A

9. B 29. D 49. C 69. C

10.C 30. D 50. C 70. B

11.C 31. D 51. D

12.A 32. B 52. B

13.B 33. B 53. D

14.D 34. B 54. D

15.A 35. B 55. D

16.B 36. B 56. A

17.B 37. B 57. B

18.B 38. A 58. C

19.B 39. A 59. C

20.B 40. C 60. A

chemistry:1990

1. In moving from left to right across a period in the periodic table of

the elements

(A) ionization energy decreases

(B) atomic radius decreases

(C) electronegativity decreases

(D) electron affinity decreases

2. Which transition is associated with the largest change in energy in the

hydrogen atom?

(A) n = 5 to n = 3

(B) n = 2 to n = 1

(C) n = 3 to n = 2

(D) n = 4 to n = 2

3. In which pair are the elements most similar in their chemical

properties?

(A) B and N

(B) Li and Fr

(C) Mg and Al

(D) S and Cl

4. A 4.0 g sample of impure Ca(NO3)2 was found to contain 0.85 g of

calcium. What percentage of Ca(NO3)2 was in the original sample? (molar

mass of Ca(NO3)2 = 164.1 g mol¯1)

(A) 13 %

(B) 36 %

(C) 64 %

(D) 87 %

5. Aluminum hydroxide, Al(OH)3, is insoluble in water, but dissolves

readily in both acidic and basic solutions. Such behavior is characteristic

of

(A) polyprotic behavior.

(B) hydrophilic behavior.

(C) amphoteric behavior.

(D) a buffer.

6. The freezing point of a 1.00 m aqueous solution of HF is found to be -

1.91 °C. The freezing point constant is water, kf, is 1.86 K m¯1. What is

the percent of dissociation of HF at this concentration?

(A) 2.7 %

(B) 5.2 %

(C) 10 %

(D) 30 %

7. Enthapies of formation cannot be measured for many compounds directly,

and must be calculated from combustion data. Given the following data,

calculate the heat of formation of glucose, C6H12O6.

C (graphite) + O2 (g) --> CO2 (g) DH = -394 kJ mol¯1

H2 (g) + 1/2 O2 (g) --> H2O (l) DH = -286 kJ mol¯1

C6H12O6 (s) + 6 O2 (g) --> 6 CO2 (g) + 6 H2O (l) DH = -2808 kJ mol¯1

(A) -1272 kJ mol¯1

(B) +1272 kJ mol¯1

(C) +2128 kJ mol¯1

(D) -3488 kJ mol¯1

8. If the enthalpy of fusion of iodine is +15.5 kJ mol¯1, and the enthalpy

of sublimaiton of iodine is +57.3 kJ mol¯1, what is the enthalpy of

vaporization of iodine?

(A) -41.8 kJ mol¯1

(B) +41.8 kJ mol¯1

(C) -72.8 kJ mol¯1

(D) +72.8 kJ mol¯1

9. If, for N2, DHvap = 5.58 kJ mol¯1 and DSvap = 72.1 J mol¯1 K¯1, at low

temperatures, in what phase will N2 be at -165 °C?

(A) gas

(B) liquid

(C) solid

(D) at the liquid/gas phase boundary

10. Which of the following molecules contains a central atom which is sp2

hybridized?

(A) H2SO4

(B) H2CO3

(C) ICl2

(D) H3CCH3

11. Which of the following molecules has at least one non-bonding pair of

electrons on the central atom?

(A) CHCl3

(B) HCN

(C) H2CO

(D) O3

12. Which of the following statements about ionic compounds is false?

(A) Ionic compounds are hard, brittle solids with high melting points.

(B) Some compounds which exhibit primarily ionic bonding in the solid

phase can form covalent bonds in the gas phase.

(C) The lattice energy is the quantity of energy required for 1 mol of

a solid ionic substance to be separated completely into gaseous ions well

removed from one another.

(D) In general the lattice energy increases as the charge on the anion

and cation increase and increases as the size of the anion and cation

decrease.

13. The pH of a saturated solution of calcium hydroxide is 12.40. What is

Ksp for this salt?

(A) 6.3 x 10¯38

(B) 1.58 x 10¯25

(C) 7.9 x 10¯6

(D) 1.58 x 10¯5

14. The mass of a nitrogen gas molecule is 14 times that of a hydrogen

molecule. What is the hydrogen molecule's velocity, relative to that of the

nitrogen molecule (VN2), if both are at the same temperature?

(A) 0.27 VN2

(B) 3.7 VN2

(C) 14 VN2

(D) 196 VN2

15. The Ksp of PbBr2 is 6.3 x 10¯6. If 50 mL of 0.020 M Pb(NO3)2 are mixed

with 50 mL of 0.010 M CaBr2, which of the following is true?

(A) the solution will not form a precipitate

(B) calcium nitrate will precipitate

(C) PbBr2 will precipitate and excess Pb2+ will remain in solution

(D) PbBr2 will precipitate and excess Br¯ will remain in solution

16. According to the phase diagram to the right, if the pressure is

increased at constant temperature, from point A, what change will occur?

(A) Solid will change to vapor

(B) Liquid will change to vapor

(C) Liquid will change to solid

(D) Solid will change to liquid

17. How many of the following salts will be more soluble in acid solution

than in pure water?

CdCO3, Mn(OH)2, PbS, PbCl2

(A) 1

(B) 2

(C) 3

(D) 4

18. A 50.0 mL sample of nitrogen gas is collected over water at 25 °C and

720 torr. What is the volume in mL of the dry gas at STP? (The vapor

pressure of water at 25 °C is 23.8 torr.)

(A) 42.0

(B) 43.4

(C) 57.6

(D) 59.6

19. To which of the following would addition of an equal volume of 0.50 M

NaOH lead to a solution having a lower pH?

(A) 0.30 M HCl

(B) water

(C) 0.60 M KOH

(D) 0.40 M NaNO3

20. Consider the solvent effect on acid dissociation. Would you expect HCl

to be weak or strong in the two solvents, water and benzene (C6H6)?

(A) strong in both

(B) weak in both

(C) strong in water, weak in benzene

(D) weak in water, strong in benzene

21. The equilibrium constant for the equation below is very small; that is,

K << 1.

HX (aq) + Y¯(aq) <===> X¯ (aq) + HY (aq)

Which statement is true?

(A) The reaction goes nearly to completion

(B) HY is a weaker acid than HX

(C) X¯ is a better proton acceptor than Y¯

(D) Y¯ is a stronger base than X¯

22. Consider the reaction 3A (g) + 2B (g) <===> C (g). Initially, only A

and C are present, each at a concentration of 0.20 M. At equillibrium, the

concentration of B is 0.10 M. What is the value of the equilibrium

constant, Kc, for the reaction?

(A) 6

(B) 43

(C) 60

(D) 350

23. Consider the system

NH4Cl (s) <===> NH3 (g) + HCl (g)

If the concentration of ammonia gas is tripled, the value of the

equilibrium constant will

(A) triple

(B) increase, buy by more than a factor of three

(C) decrease to one-third its value

(D) remain the same

24. The weak base ionization constant (Kb) for hydroxylamine, HONH2, is 1.1

x 10¯8. Which of the following equations best describes its ionization

equilibrium?

(A) HONH2 (aq) + H2O (l) ---> HONH3+ (aq) + OH¯ (aq)

(B) HONH2 (aq) ---> NH2+ (aq) + OH¯ (aq)

(C) HONH2 (aq) + H2O (l) ---> ONH2¯ (aq) + H3O+ (aq)

(D) HONH2 (aq) + H3O+ (aq) ---> HONH3+ (aq) + H2O (l)

25. Which substance, when added to water, will NOT change the pH?

(A) NaHCO3

(B) NH4Cl

(C) KCN

(D) KCl

26. How many O2 molecules are contained in 2.0 liters of oxygen gas at 27

°C and 3.0 atm pressure?

(A) 1000

(B) 1.5 x 1023

(C) 1.5 x 1024

(D) 2.5 x 1024

27. What is the vapor pressure of an isopropanol solution containing 80.0 g

of the nonvolatile solute glycerol (C3H8O3, molar mass = 92.0 g mol¯1) and

212 g is isopropanol (C3H8O, molar mass = 60.0 g mol¯1) at 68 °C? (The

vapor pressure of isopropanol at 68 °C is 400 torr.)

(A) 79

(B) 212

(C) 321

(D) 400

28. If 40.0 mL of 0.20 M CH3COOH are titrated with 0.20 M NaOH, how many mL

of base must be added to form a buffer solution with the greatest buffering

capacity?

(A) 5.0

(B) 10.0

(C) 20.0

(D) 40.0

29. An important reaction in the production for nitrogen fertilizers is

4NH3 (g) + 5O2 (g) --> 4NO (g) + 6 H2O (g)

At constant temperature and pressure, what is the maximum number of liters

of NO (g) that can be produced from 14.0 L of NH3 and 16.0 L of O2?

(A) 12.8

(B) 14.0

(C) 17.5

(D) 20.0

30. Which of the following graphs for an ideal gas, when all other

variables are held constant, will NOT yield a straight line?

(A) P versus 1/V

(B) V versus T

(C) n versus T

(D) P versus T

31. What is the equilibrium constant for a reaction that has a value of DG

= - 41.8 kJ at 100 °C?

(A) -5.87

(B) 1.4 x 10¯6

(C) 13.5

(D) 7.1 x 105

32. How much heat must be removed from a 10.0 g ingot of stainless steel in

order to lower its temperature from 60.0 °C to 35.0 °C? (The specific heat

of stainless steel is 0.51 J g¯1 K¯1.)

(A) 128 J

(B) 179 J

(C) 306 J

(D) 409 J

33. What is the standard molar entropy change, DS, for the synthesis of

ammonia, using the following data.

1/2 N2 (g) + 3/2 H2 (g) ---> NH3 (g)

S° (J K mol¯1) 192 131 193

(A) -99.5 J K¯11

(B) -130 J K¯1

(C) +130 J K¯1

(D) +516 J K¯1

34. Which of the following reactions is accompanied by a decrease in

entropy?

(A) H2O (l) ---> H2O (g)

(B) C2H2 (g) + 2 H2 (g) ---> C2H6 (g)

(C) NH4Cl (s) + H2O ---> NH4Cl (aq)

(D) H2 (g) + Cl2 ---> 2 HCl

35. Trouton's Rule, which states that font face="Symbol">DHvap / Tbp = 85 J

mol¯1 K¯1 (a constant) for nonpolar liquids, relates to the entropy change

for the vaporization process, DSvap. Knowing this, how would the value for

water differ from this constant?

(A) It would be smaller than 85 J mol¯1 K¯1.

(B) It would be larger than 85 J mol¯1 K¯1.

(C) It would also be 85 J mol¯1 K¯1.

(D) It is impossible to predict.

36. At equilibrium, the Gibbs free energy function of a reaction, DG, has a

value

(A) greater than zero.

(B) less than zero.

(C) equal to zero.

(D) which depends on the particular system.

37. An ammonia solution has a density of 0.910 g cm¯3 and is 25.0% NH3 by

mass. What is the molarity of the solution?

(A) 12.1 M

(B) 13.4 M

(C) 14.5 M

(D) 15.5 M

38. Which of the following molecules has a measurable dipole moment?

(A) BrF3

(B) XeF4

(C) CF4

(D) PCl5

39. Which type of crystal structure best describes that present in diamond?

(A) ionic

(B) covalent

(C) metallic

(D) extended molecular

40. Which of the following substances has the highest melting point?

(A) KCl

(B) ClO2

(C) CaO

(D) BiCl3

41. Which of the following does not define a covalent bond?

(A) a shared pair of electrons

(B) an overlap of half-filled atomic or hybrid orbitals

(C) increased electron density in the region between atoms of two

nonmetals

(D) electrostatic attraction between species in which one or more

electrons have been transferred

42. How many equivalent contributing resonance forms does the ion NO3¯

have?

(A) 1

(B) 2

(C) 3

(D) 4

43. Which compound is the anhydride of sulfurous acid?

(A) SO4

(B) SO3

(C) SO2

(D) Na2SO4

44. Which is the most accurate description of Na+ species in dilute aqueous

solution?

(A) the nearest neighbor is a Cl¯ ion

(B) the nearest neighbor is the positive end of the water dipole

(C) the nearest neighbor is the negative end of the water dipole

(D) there are no interactions with any species in the solution

45. Which of the following oxides, at the same concentration when dissolved

in water, results in the most acidic solution?

(A) CO2

(B) B2O3

(C) N2O5

(D) Li2O2

46. Which of the following salts should form a colorless solution when

dissolved in water?

(A) CuCl2

(B) FeCl3

(C) CrCl3

(D) CaCl2

47. Which of the following can act as a Lewis base?

(A) BF3

(B) CH4

(C) PH3

(D) NH4+

48. The shape of the phosphite ion, PO33¯, is best described as

(A) tetrahedral.

(B) trigonal planar.

(C) trigonal pyramidal.

(D) bent.

49. What is the ground state electron configuration of the Mn2+ ion?

(A) [Ar] 4s1 3d5

(B) [Ar] 4s2 3d3

(C) [Ar] 3d5

(D) [Ar] 3d4

50. Which group of metals has the lowest melting points?

(A) alkali metals

(B) alkaline earth metals

(C) transition metals

(D) lanthanide metals

51. Which solution has the highest electrical conductivity?

(A) 0.05 M KCl

(B) 0.05 M HF

(C) 0.05 M NH3

(D) 0.05 M CaCl2

52. Which of the following compounds exhibit geometric isomerism?

I. CH3CH=CHCH2CH3

II. CH2=CHCl

III. CH3CH=CHCl

(A) I and III

(B) I and II

(C) II and III

(D) I, II, and III

53. What hybrid orbitals are used by each nitrogen atom in N2F2?

(A) sp

(B) sp2

(C) sp3

(D) p only

54. From the Lewis structures given below, choose the invalid one.

55. The compounds Br2 (159.8 g mol¯1) and ICl (162.4 g mol¯1) have similar

molar masses, yet ICl boils at 97 °C and Br2 boils at 59 °C. Which

statement best explains this difference?

(A) ICl has a longer bond that Br2.

(B) ICl is ionic, while Br2 is covalently bonded.

(C) ICl has a measurable dipole movement, but Br2 does not.

(D) ICl has a stronger bond than Br2.

56. Which one of the following salts is expected to give a red color in a

flame test?

(A) KCl

(B) NaCl

(C) CaCl2

(D) BaCl2

57. Which of the following metals exhibits the greatest variety of

oxidation states?

(A) Ba

(B) Y

(C) Cr

(D) Tl

58. In spontaneous beta particle (b¯) emission, what is the source of the

emitted electron?

(A) the nucleus

(B) the 1s orbital

(C) the outermost occupied orbital

(D) a random orbital

59. Which one of the compounds below is classified as a peroxide?

(A) MgO

(B) Na2O

(C) BaO2

(D) KO2

60. Which of the following sets of ions is generally associated with "hard"

water?

(A) Na+, Ca2+

(B) Na+, K+

(C) Ca2+, Mg2+

(D) Mg2+, SO42¯

61. The boiling points of four liquids are shown. Which liquid has the

highest vapor pressure at 25 °C?

Compound Boiling Point

ethyl ether 35 °C

acetone 56 °C

ethanol 78 °C

water 100 °C

(A) ethyl ether

(B) acetone

(C) ethanol

(D) water

62. Which term best describes a 0.10 M solution of Fe(NO3)3?

(A) saturated

(B) neutral

(C) acidic

(D) basic

63. Very strong acids, such as HNO3 and HCl, appear to be equally strong in

water. This "leveling effect" of water occurs because

(A) OH¯ is a stronger base than the conjugate bases of HNO3 and HCl.

(B) H3O+ is a stronger acid than HNO3 and HCl.

(C) H2O is a base than the conjugate bases of HNO3 and HCl.

(D) H2O is a weaker base than the conjugate bases of HNO3 and HCl.

64. If the equilibrium P4(g) + 6 Cl2(g) <===> 4 PCl3(g) is established by

adding equal numbers of moles of P4 and Cl2 to an evacuated flask, which of

the following must be true at equilibrium?

(A) [Cl2] > [PCl3]

(B) [Cl2] < [P4]

(C) [PCl3] > [P4]

(D) [P4] = [PCl3]

65. Consider the equilibrium NH4HS(s) <===> NH3(g) + H2S(g). A 4.65 g

sample of solid NH4HS is placed in an evacuated 3.0 L flask at 35 °C and

allowed to reach equilibrium at which time the total pressure in the flask

is 0.82 atm. What is the value of Kp at this temperature?

(A) 0.67

(B) 0.41

(C) 0.17

(D) 0.45

66. When propanol, CH3CH2CH2OH, is oxidized to propanoic acid, CH3CH2COOH,

what is the number of electrons on the right side of the half-reaction?

(A) 2

(B) 3

(C) 4

(D) 5

67. What is the [Cu2+] in the cell Zn / Zn2+ (0.05 M) // Cu2+ (X M) / Cu if

the cell voltage is 1.03 V?

(A) 0.12 M

(B) 0.0002 M

(C) 0.05 M

(D) 0.0035 M

68. Ten amperes are passed through molten aluminum chloride for 5.5 hours.

How many grams of aluminum metal could be produced by this electrolysis?

(A) 18.5

(B) 55.4

(C) 91.2

(D) 273

69. What is the DG° for the reaction 2 Al3+ + 6 I¯---> 2 Al + 3 I2, at 298

K?

(A) +1300 kJ

(B) -650 kJ

(C) -420 kJ

(D) 650 kJ

70. How many of the following would shift this reaction to the right?

PbO2(s) + 4 H+ + Cu(s) ---> Pb2++ 2 H2O + Cu2+

Acid is added.

PbO2 is added.

The [Pb2+] is increased.

The pH is increased.

Sulfide ion is added.

(A) 1

(B) 2

(C) 3

(D) 4

answers

answers to this paper is also not available

chemistry :1989:

1. Gallium reacts with element Y to form a compound with the formula GaY.

If barium were to combine with element Y, the formula of the product would

most likely be

(A) BaY

(B) Ba2Y

(C) Ba2Y3

(D) Ba3Y2

2. The number of significant figures one can assume in the atomic weight of

12C is

(A) 2

(B) 3

(C) 4

(D) unlimited

3. A compound X2O3 contains 31.58% oxygen by weight. The atomic weight of X

is

(A) 34.66 g/mol.

(B) 45.01 g/mol.

(C) 52.00 g/mol.

(D) 104.0 g/mol.

4. The emission spectrum of the hydrogen atom

(A) is caused by the removal (ionization) of the electron.

(B) is continuous because the electron can emit any frequency of light

during a transition.

(C) is caused by the absorption of light at characteristic frequencies

the electron to be excited into higher energy levels.

(D) is a result of the excited electron undergoing transitions to lower

energy levels and emitting photons of light at specific frequencies.

5. Cathode rays are

(A) a beam of positively charged particles.

(B) nuclei of helium atoms.

(C) fast-moving neutrons.

(D) streams of electrons.

6. Which atom has the correct ground state electron configuration?

(A) Cl: [Ne]3s1 3p6

(B) Mo: [Kr]5s1 4d5

(C) Cu: [Ar]4s2 3d8

(D) As: [Ar]4s2 4d10 4p3

7. The correct number of unpaired electrons in the ground state of a

neutral cobalt atom is:

(A) 1

(B) 2

(C) 3

(D) 4

8. Which electron configuration describes a neutral atom in an excited

state?

(A) [Xe] 6s< sup> 4f14 5d10 6p3

(B) [He] 2s1

(C) [Ne] 3s1 3p1

(D) [Ar] 4s1 3d5

9. The first ionization potential for S is lower than the first ionization

potential for P because

(A) Hund's rule is violated.

(B) ionization potentials decrease across a representative period.

(C) half-filled and filled sets of orbitals are more stable than

configurations of one more or fewer electrons.

(D) The statement above is false. The first ionization potential for S

is higher than that for P.

10. Which set of quantum numbers describe the most easily-removed electron

from a neutral iron atom?

(A) n = 4, l = 0, m = 0, s = -1/2

(B) n = 3, l = 2, m = 0, s = +1/2

(C) n = 3, l = 2, m = -1, s = -1/2

(D) n = 1, l = 0, m = 0, s = -1/2

11. The molecular ion XF2¯ has three pairs of non bonding electrons around

the central atom. The bond angle F-X-F will be closest to

(A) 180°.

(B) 120°.

(C) 109°.

(D) 90°.

12. Which species has a pyramidal structure?

(A) ClO2

(B) ClO2¯

(C) ClO3¯

(D) ClO4¯

13. Which molecule is polar?

(A) CO2

(B) SF6

(C) BCl3

(D) SF4

14. Which of the following sets have correctly matched each molecule or ion

and its geometry?

Tetrahedral Trigonal

Pyramidal T-shaped Square

Planar

(A) CH4 BCl3 NO3¯ SO42¯

(B) SO42¯ NF3 ICl3 XeF4

(C) CH4 NO3¯ GaI3 SnCl4

(D) CCl4 PF3 ICl3 SF4

15. Which Lewis structure is correct?

16. The Lewis structure for dimethyformamide (a useful solvent) is shown

below:

How many C and N atoms are sp3, sp2, and sp hybridized?

(A) 4 (sp3), 0 (sp2), 0 (sp)

(B) 3 (sp3), 0 (sp2), 1 (sp)

(C) 3 (sp3), 1 (sp2), 0 (sp)

(D) 2 (sp3), 2 (sp2), 0 (sp)

17. Consider the reaction 2 Al(s) + 3 Cl2(g) ---> 2 AlCl3(s). What volume

of chlorine at STP reacts with 324 g of aluminum?

(A) 121 L

(B) 134 L

(C) 260 L

(D) 403 L

18. How many liters of H2(g) at 273 °C and 200 torr can be obtained form

the reaction of 500 g of zinc with excess hydrochloric acid?

(A) 5.12 L

(B) 343 L

(C) 650 L

(D) 1300 L

19. What is the concentration of a solution prepared by dissolving 4.20

grams of NaF in 500 grams of water?

(A) 0.00840-molal

(B) 0.00840-molar

(C) 0.200-molal

(D) 0.200-molar

20. 10.24 mL of 0.568 M Al(NO3)3 is mixed with 3.12 mL, of 4.16 M NaOH. How

much solid Al(OH)3 could be formed?

(A) 0.055 g

(B) 0.075 g

(C) 0.111 g

(D) 0.166 g

21. The standard heat of formation of ammonia gas is -46.1 kJ mol¯1. How

much heat will be produced when 3.04 gram of N2 reacts with 6.04 g of H2?

(A) 5.00 kJ

(B) 10.00 kJ

(C) 92.1 kJ

(D) 185.3 kJ

22. At 25 °C and 1 atm, the densities of neon and krypton are 0.82 and 3.42

grams/liter, respectively. The density of argon at the same temperature and

pressure is estimated to be

(A) 2.12 g/L

(B) 2.60 g/L

(C) 2.80 g/L

(D) 4.17 g/L

23. When the hydrocarbon propane is burned in air, carbon dioxide and water

are formed as in the equation

C3H8(g) + 5 O2(g) ---> 3 CO2(g) + 4 H2O(l)

If 0.100 mol of CO2 is produced, how many drops of water will be formed,

assuming one drop is 0.05 cm3 and contains 1.70 x 1021 water molecules?

(A) 2.21 x 10¯1

(B) 0.133

(C) 26.6

(D) 47.2

24. According to the kinetic molecular theory of gases, the Kelvin

temperature of a gas is directly proportional to

(A) the average velocity of the gas molecules.

(B) the square of the mass of the gas molecules.

(C) the average kinetic energy of the gas molecules.

(D) the square root of the average velocity of the gas molecules

25. Which is the most viscous at 20 °C and 1.00 atm?

(A) acetone

(B) hexane

(C) tetramethylsilane

(D) water

26. In the van der Waals equation given below,

[P + a (n/V)2] (V - nb) = nRT,

the a(n/V)2 and - nb terms represent, respectively, corrections for

(A) derivations in the pressure and the temperature.

(B) intermolecular attractive forces and inelastic collisions.

(C) intermolecular attractive forces and molecular volumes

(D) intermolecular repulsive forces and high temperatures.

27. The Bragg equation yields

(A) rates of flow of liquids.

(B) interatiomic distances in crystals

(C) trajectories of electron beams

(D) frequencies of spectral lines.

28. The empirical formula for a compound with a cubic close-packed

arrangement of anions and with cations occupying the octahedral sites is

(A) AB

(B) A2B

(C) AB2

(D) AB3

29. The structure of ice is best described as

(A) a solid network of covalently bounded atoms.

(B) cubic-close packed with 74% of the available sites occupied.

(C) an open structure because of elaborate hydrogen bonding

(D) a flickering cluster of molecules in which protons are easily

transferred through the lattice.

30. The structure of glass is best described as

(A) crystalline

(B) fluid

(C) amorphous

(D) close-packed

31. Which solution has the lowest freezing point?

(A) 1.0 molal FeCl3

(B) 1.0 molal HCl

(C) 1.0 molal KCl

(D) 1.0 molal MgCl2

32. An aqueous solution is 1.00 molal in KI. Which change will cause the

vapor pressure of the solution to increase?

(A) addition of water

(B) addition of NaCl

(C) addition of Na2SO4

(D) addition of 1.00 molal KI.

33. Find the boiling point of a solution of 5.00g of naphthalene (C10H8) in

100 g of benzene. Kb of benzene is 2.53 °C / m; the normal b.p. of benzene

= 80 °C.

(A) 0.99 °C

(B) 79 °C

(C) 81 °C

(D) 85 °C

34. What is the degree of ionization of the acid HB if a 0.120 molal

solution of HB freezes at -0.300 °C? Kf for water = 1.86 °C / m.

(A) 1.3%

(B) 6%

(C) 21%

(D) 34%

35. Given the standard enthalpies of formation : CO (g), -110.5 KJ/mol;

CO2(g), -393.5 KJ/mol. The enthalpy change for the reaction

2CO(g) + 2 CO2 (g) --> 4 C(s) + 3 O2 (g)

is

(A) -1008 kJ

(B) -566 kJ

(C) -504 kJ

(D) +1008 kJ

36. If DH° of vaporization for a liquid is 10.0 kJ / mol and DS° of

vaporization is 37.6 J / mol-K, which is the nearest to the normal boiling

point of the liquid?

(A) 240 K

(B) 266 K

(C) 300 K

(D) 310 K

37. A reaction has positive values of both DS° and DH°. From this you can

deduce that the reaction

(A) must be spontaneous at any temperature.

(B) cannot be spontaneous at any temperature.

(C) will be spontaneous only at low temperatures.

(D) will be spontaneous only at high temperatures.

38. When NH4NO3 dissolves in water, the solution becomes cold. From this

you can deduce that the DS° for the process is

(A) negative

(B) zero

(C) positive

(D) undeterminable from the data.

39. The distribution coefficient, KD, for an organic compound between water

and methylene chloride is 3.40. An aqueous solution of the organic compound

contains 0.500 g per 100 mL and is extracted with 50.0 mL of methylene

chloride. What percentage of the organic compound originally in the water

is extracted?

(A) 31.5%

(B) 63.0%

(C) 72.0%

(D) 92.6%

40. Which compound is soluble in 8 M NaOH?

(A) Fe(OH)3

(B) Al(OH)3

(C) Mn(OH)2

(D) Ni(OH)2

41. Which substance can be used to separate Cu2+ from Mg2+ in an aqueous

solution containing Cu(NO3)2 and Mg(NO3)2?

(A) HCl

(B) H2S

(C) HClO3

(D) H2SO4

42. Magnesium fluoride is a slightly soluble salt whose solubility product

constant is Ksp = 3.7 x 10¯8. What is the approximate solubility of

magnesium flouride?

(A) 9.2 x 10¯9 M

(B) 1.2 x 10¯8 M

(C) 1.4 x 10¯4 M

(D) 2.1 x 10¯3 M

43. Al(OH)3 is an insoluble solid whose Ksp = 1.9 x 10¯33. What is the

maximum concentration of OH¯ which can exist in 0.10 M AlCl3 solution

without causing Al(OH)3 to precipitate?

(A) 2.7 x 10¯11 M

(B) 1.4 x 10¯10 M

(C) 8.7 x 10¯8 M

(D) 3.1 x 10¯7 M

44. MY and NY3, two nearly insoluble salts, have the same Ksp values of 6.2

x 10¯13 at room temperature. Which statement would be true in regard to MY

and NY3?

(A) The molar solubilities of MY and NY3 in water are identical.

(B) The molar solubility of MY in water is less than that of NY3.

(C) The salts MY and NY3 are more soluble in 0.5 M KY than in pure

water.

(D) The addition of the salt of KY to solution of MY and NY3 will have

no effect on their solubilities.

45. HCN is a weak acid (Ka = 4.0 x 10¯10). Which statement is NOT true for

an aqueous solution of hydrocyanic acid?

(A) The [H+] decreases as solution of HCN are made more dilute.

(B) Its percent dissociation increases as solutions are made more

dilute.

(C) In a 0.100 M solution of HCN, the HCN is approximately 6.3%

dissociated.

(D) The ionization constant, Ka, varies dramatically over a range of

concentrations of HCN.

46. Given a weak monoprotic acid such as HCN at equilibrium in aqueous

solution, the addition of a strong acid such as HBr to the solution would

cause

(A) no change in the concentration of H+ or CN¯.

(B) the concentrations of both HCN and CN¯ concentration to increase.

(C) the HCN concentration to increase and the CN¯ concentration to

decrease.

(D) the HCN concentration to decrease and the CN¯ concentration to

increase.

47. Which solution has pH value above 7.00?

(A) 0.10 M KCI

(B) 0.10 M NH4NO3

(C) 0.10 M KCN

(D) 0.10 M HI

48. Which of the following would you expect to have the strongest conjugate

acid?

(A) NH3

(B) SO42¯

(C) PO43¯

(D) NH2¯

49. If weak base has the ionization constant, Kb, Then the value of the

ionization constant, Ka, of its conjugate acid is given by

(A) 1/Kb

(B) Kw/Kb

(C) Kb/Kw

(D) Kw/Ka

50. Which mixture is a buffer solution?

(A) 0.10 M HI + 0.10 M KI

(B) 0.10 M KCl + 0.10 M NaCl

(C) 0.10 M NaCN + 0.10 M HCN

(D) 0.10 M NaOH + 0.10 M KOH

51. Ethanol is CH3CH2OH. Which species is formed when ethanol acts as a

Bronsted base?

(A) CH3CH2O¯

(B) CH3CH2+

(C) CH3CH2OH2+

(D) H3O+

52. If molten CaCl2 is electrolyzed, the anode reaction is

(A) Ca2+ + 2e¯ ---> Ca

(B) 2Cl¯ ---> Cl2 + 2e¯

(C) CaCl2 ---> Ca + Cl2

(D) 2H2O ---> O2 + 4H+ + 4e¯

53. The permnganate ion is an excellent oxidizing agent in aqueous

solutions. When the half-reaction

MnO4¯ + H+ + e¯ ---> MnO2 + H2O

is balanced, the correct coefficients for the species involved are

(A) 1,4,4,1,2

(B) 1,4,2,1,2

(C) 1,4,3,1,2

(D) 1,4,1,1,2

54. A fuel cell uses H2(g) and Cl2(g) to form HCl(aq, 1M). Given the

standard electrode potential:

Cl2(g) + 2e¯ ---> 2Cl¯(aq) ; E° = 1.36 V,

What is the maximum electrical work per mole of HCl produced possible from

this cell?

(A) 1.36 J

(B) 131,2 kJ

(C) 262,4 kJ

(D) 96,500 kJ

55. Given the standard electrode potentials:

Sn4+ (aq) + 2e¯ ---> Sn2+ (aq) E° = 0.154 V

Br (aq) + 2e¯ ---> 2Br¯ (aq) E° = 1.087 V

The equilibrium constant for the process

2Br¯ (aq) + Sn4+ (aq) ---> Br2(aq) + Sn2+ (aq)

is

(A) 1.19 x 10¯42

(B) 3.02 x 10¯32

(C) 3.31 x 1031

(D) 8.40 x 1041

56. The rate of the reaction 2NO + Cl2 ---> 2NOCl is given by the rate

equation rate = k[NO]2[Cl2]. The value of the rate constant can be

increased by

(A) increasing the concentration of the NO.

(B) increasing the concentration of the Cl2.

(C) increasing the temperature.

(D) doing all of these.

57. For a certain reaction the rate law is rate = k[C]3/2. If the rate of

the reaction is 0.020 mol L¯1 s¯1 when [C] = 1.0 M, what is the rate when

[C] = 0.60 M?

(A) 0.0093 mol L¯1 s¯1

(B) 0.012 mol L¯1 s¯1

(C) 0.033 mol L¯1 s¯1

(D) 0.040 mol L¯1 s¯1

58. The rate of the reaction 2A + B ---> Products is consistent with the

rate equation rate = k[A][B]. Which reaction mechanism is consistent with

this information?

(A) A + B ---> AB (slow)

AB + A ---> Products (fast)

(B) A + A ---> A2 (slow)

A2 + B ---> Products (fast)

(C) A + B ---> AB (fast)

(D) A + A ---> A2 (fast)

A2 + B ---> Products (slow)

59. Starting with three different kinds of amino acids, how many different

kinds of tripeptide molecules can be made assuming each amino acid can be

used more then once in a molecule if desired?

(A) 3

(B) 6

(C) 9

(D) 27

60. Metallic zinc will not reduce

(A) Cu2+

(B) H+

(C) Ag+

(D) Al3+

61. What is the pH of the solution that results when 10.0 mL of 0.10 HF

(Ka= 6.7 x 10¯4) and 10.0 mL of 0.040 M NaOH are mixed?

(A) 1.0

(B) 1.2

(C) 1.5

(D) 3.0

62. A saturated fat is

(A) a substance containing only carbon dioxide and hydrogen.

(B) a fat containing C=C bonds

(C) a substance in which the fat is at its maximum concentration in a

solvent .

(D) the primary constitutent of proteins.

63. The principal used of hydrofluoric acid is

(A) in etching glass.

(B) as a bleaching agent.

(C) as an extremely stong oxidizing agent.

(D) in the preparation of organic fluorine compounds.

64. Important commerical extraction processes as welll as analytical

techniques utilize carbon dioxide above its critical temperature. Under

theses conditions

(A) carbon dioxide is no longer fluid.

(B) one cannot condense the gas to a separate liquid state by applying

pressure.

(C) carbon dioxide is known commonly as dry ice.

(D) carbon dioxide dissociates readily into C and O2.

65. The amount of copper in a 2.00 gram sample of the mineral cuprite was

determined by dissolving the sample in nitric acid (HNO3) and adding an

excess of iodide (I¯) solution to the resultant copper nitrate [Cu(NO3)2]

solution. The iodine (I2) liberated required 15.7 mL of 0.200 molar sodium

thiosulfate (Na2S2O3) solution to be titrated to an end point. What is the

percentage of Cu in the mineral? The essential reactions are:

2Cu2+ + 4I¯ ---> 2CuI + I2

I2 + 2S2O32¯ ---> S4O62¯ + 2I¯

(A) 5.0%

(B) 10%

(C) 20%

(D) 40%

66. A mixture of n-hexane (C6H14) gas and O2 gas was inside the vessel was

340 torr. After ignition by a spark, the mixture reacted completely to form

CO gas, CO2 gas, and steam. The total pressure exerted by the gaseous

products in the vessel was then 520 torr when the temperature was restored

to 297 °C. Which of the following equations describes the reaction that

took place in the vessel?

(A) C6H14 + 8 O2 ---> 3 CO + 3 CO2 + 7 H2O

(B) C6H14 + 7 O2 ---> 5 CO + CO2 + 7 H2O

(C) 2 C6H14 + 17 O2 ---> 4 CO + 8 CO2 + 14 H2O

(D) 2 C6H14 + 15 O2 ---> 8 CO + 4 CO2 + 14 H2O

67. When conducting analyses of substances that are weak acids by titrating

solutions with a standardized strong base, the end-point indicator is

chosen so that

(A) its color change occurs around the neutralization pH of 7.00.

(B) its color change occurs when the pH is about the same as the pKa of

the weak acid.

(C) its color change occurs at a pH that is more basic than pH = 7.00.

(D) its color change occurs at a pH that is the same as that of the

standardized base solution.

68. Given the following standard enthalpies of formation in kJ mol¯1: CH4

(g), -74.8; C2H2(g), 226,9; C2H4(g), 52.6; C2H6(g), -84.5; CO2(g), -393.5;

H2O(l), -285.8. Which hydrocarbon, when burned in an excess of oxygen will

give the greatest heat per gram of fuel burned?

(A) CH4

(B) C2H2

(C) C2H4

(D) C2H6

69. A solution may contain NaOH, Na2CO3, NaHCO3 individually or as any pair

of the three analytes. A 25.00 mL aliquot of the solution is treated with a

standard solution of HCl. Given the following information, what analyte(s)

are present in the solution? Addition of phenolphthalein indicator (pink at

pH = 10.0 and colorless at pH =8.3) to the solution gives a pink color. The

solution becomes colorless after the methyl purple indictor (green at pH =

5.4 and purple at pH = 4.8) to this solution gives a green color. Addition

of an additional 15.30 mL of 0.1000 M HCl causes the solution to become

purple in color.

(A) NaOH + NaCO3

(B) NaCO3 + NaHCO3

(C) NaHCO3

(D) NaOH

70. A student standardizes a solution of HCl versus the primary standard

Na2CO3. He obtains the following values of the molarity of the HCl: 0.1055,

0.0998, 0.1032, 0.0995, 0.0990. What is the relative standard deviation

(RSD) of his data expressed in parts per thousand (ppt)?

(A) 5 ppt

(B) 12 ppt

(C) 24 ppt

(D) 27 ppt

1. (14pts.) A 1.529 gram of unknown ester is hydrolyzed in 50.00 ml of

0.236 M NaOH solution according to the reaction below:

RCO2R'(l) + Na+(aq) + OH¯(aq) --->RCO2¯(aq) + Na+(aq) + R'OH(l)

When the reaction is complete, the excess OH¯ ion remaining in this

solution is titrated with a 0.115 M HCl solution. The volume of HCl

required in this back-titration is 27.83 ml.

(a) How many moles of HCl are consumed during the back-titration?

(b) How many moles of NaOH reacted with the ester?

(c) Calculate the molar mass of the ester.

(d) If the molar mass of the alcohol is 74 g/mol, calculate the molar

mass of the acid which can be obtained by acidifying the final solution.

(e) Write structural formulas for all possible isomers of the alcohol.

2. (10pts.) Three samples of magnesium(II) sulfate hydrate were heated and

the following results were obtained.

TIME HEATED

10 min.

(Sample No. 1) 20 min.

(Sample No. 2) 30 min.

(Sample No. 3)

Mass of hydrate 1.762 g 1.351 g 1.097 g

Mass heated salt 1.006 g 0.660 g 0.538 g

Mass water lost 0.756 g 0.691 g 0.559 g

(A) Calculate the percentage of the water that was originally present

in each sample.

(B) What percentage of water should be reprted for the magnesium

sulfate hydrate? Why?

(C) How can you tell when you have heated a sample long enough?

(D) calculate the number of moles of water per mole of magnesium

sulfate in the hydrate.

3. (14pts.) The pH of a 0.65 M solution of HF is 1.66.

(A) Calculate the ionization constant for HF.

(B) Calculate the pH of the solution which resultss when 15.00 mL of

0.42 M NaOH are added to 25.00 mL of 0.65 M HF.

(C) Calculate the [Ca2+] required to initiate the precipitation of CaF2

in the solution in (b). (Ksp = 3.9 x 10¯11)

(D) Calculate the pH of the solution when 25.00 mL of 0.65 M HF is just

neutralized with 0.15 M NaOH.

4. (12pts.) Mixtures of hydrazine (N2H4) and dinitrogen tetroxide (N2O4)

have been used as rocket fuels due to their reaction to form N2 and H2O.

The enthalpies of formation of these substances are:

DHf° (kJ/mol)

N2H4 50.6

N2O4 9.16

H2O -241.8

N2 ---

(A) Write a balanced chemical equation for the reaction of hydrazine

and dinitrogen tetroxide to form nitrogen and water.

(B) Calculate the enthalpy change for the reaction in (a).

(C) Calculate the heat which would be released if 0.0800 moles of N2H4

is reacted with a stoichiometric amount of N2O4.

(D) If 3.36 grams of N2 and 2.88 grams of H2O are produced in the

reaction in (c), calculate the temperature to which these gases would be

heated if the specific heats of N2 and H2O are 1.04 J / g-K and 1.87 J / g-

K, repectively. (Assume that the heat released contributes only to

increasing the temperature of the gaseous products and not of the

container. Assume also that the specific heats of N2 and H2O do not vary

with temperature.)

5. (16 pts.) Write equations for the following reactions.

(A) Concentrated sodium hydroxide solution is added to solid ammonium

chloride.

(B) A solution of potassium bromide is added to a solution of

Mercury(I) nitrate.

(C) Titanium(IV) chloride is added to excess water.

(D) Equimolar quantities of chlorine and toluene (methylbenzene) are

mixed in the presence of iron(III) chloride in the dark.

(E) Solutions of potassium permanganate and tin(II) chloride are mixed.

(F) Radon-220 decays with the loss of an alpha particle.

(G) Excess sodium hydroxide is added to a solution of aluminum nitrate.

(H) Carbon dioxide is bubbled through a solution of calcium hydroxide.

6. (12 pts.) Account for the following observations:

(A) Calcium exhibits an oxidation state of +2 in virtually all its

compounds even though the energy required to remove the second electron

from a Ca atom is twice as great as that required to remove the first.

(B) the melting point of MgO is 2800 °C while that of NaF is 993 °C

even though the interionic distances are within 10% of one another (2.10 x

10¯8 cm for MgO and 2.31 x 10¯8 cm for NaF).

(C) The F-E-F bond angles in the compounds ClF3, NF3, and BF3 are 90°,

101° and 120°, respectively.

(D) HF is a stronger acid than NH3 but a weaker acid than HCl even

though the electronegativity of fluorine (4.0) is greater than those of

nitrogen and chlorine, which are almost the same (3.1 and 2.9,

respectively).

7. (12pts.) The standard reduction potentials for a series of technetium

species are:

TcO4¯ ---> TcO3 0.65 volt

TcO4¯ ---> Tc2+ 0.57 volt

TcO3 ---> TcO2 0.83 volt

TcO2 ---> Tc2+ 0.28 volt

Tc2+ ---> Tc -0.50 volt

(A) Identify the reactions whose potentials would be affected by pH

change and explain your answer.

(B) Compare the relative oxidizing ability of the TcO4¯ in its reaction

to form the Tc2+ ion with that of the MnO4¯ ion when it forms the Mn2+ ion

(E° = 1.51 volts). Explain your answer.

(C) Identify the species which would be thermodynamically unstable

toward disproportionation and explain your reasoning.

(D) Predict the product formed when technetium metal is added to 1.0 M

HCl and explain your reasoning.

8. (10pts.) Metal oxides are often referred to as bases and nonmetal oxides

as acids.

(A) Explain why.

(B) Write chemical equations which illustrated the basicity of a metal

oxide and the acidity of a nonmetal oxide.

(C) Which oxide is more basic? Cr2O3 or CrO3? Why?

(D) Which oxide is more basic? Al2O3 or In2O3? Why?

answers

1.D 21.B 41.B 61.C

2.D 22.A 42.D 62.B

3.C 23.D 43.A 63.D

4.D 24.C 44.B 64.B

5.D 25.D 45.D 65.B

6.B 26.C 46.C 66.D

7.C 27.B 47.C 67.C

8.C 28.A 48.B 68.A

9.C 29.C 49.B 69.A

10.A 30.C 50.C 70.D

11.A 31.A 51.C

12.C 32.A 52.B

13.D 33.C 53.C

14.B 34.D 54.B

15.B 35.D 55.B

16.C 36.B 56.C

17.D 37.D 57.A

18.D 38.C 58.A

19.C 39.B 59.D

20.D 40.B 60.D

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chemistry :1988