Chem 124 Exam 1 Spring 2016 Version 1 Name___________________________________

TOTAL POINTS - 116MULTIPLE CHOICE 1.4 POINTS EACH

1) A molecule containing a central atom with sp3 hybridization has a(n) ________ electron geometry.A) linearB) tetrahedralC) octahedralD) bentE) trigonal bipyramidal

2) What is the bond order in He2 molecule?A) 0 B) 2 C) 1 D) 1/2

3) Which will make the molecule AB2 bent in shape?A) the nonbonding electrons B) the bonding electronsC) the lone pairs on atom A D) the bond pairs

4) Identify the characteristics of a liquid.A) definite shape and volumeB) indefinite shape and volumeC) indefinite shape, but definite volumeD) none of the aboveE) all of the above

5) Give the change in condition to go from a liquid to a gas.A) Increase heat or increase pressure.B) Increase heat or reduce pressure.C) Cool or reduce pressure.D) Cool or increase pressure.E) None of the above

6) Which of the following statements is true?A) Energy is given off when the attraction between two molecules is broken.B) Intermolecular forces are generally stronger than bonding forces.C) Until a certain point, the potential energy of molecules decrease as they get closer to one another.D) Increasing the pressure on a solid usually causes it to become a liquid.E) None of the above are true.

7) What is the strongest type of intermolecular force present in CHF3?A) hydrogen bondingB) ion-dipoleC) dipole-dipoleD) dispersionE) None of the above

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8) What type of intermolecular force causes the dissolution of NaCl in water?A) ion-dipole forceB) dispersion forcesC) hydrogen bondingD) dipole-dipole forcesE) None of the above

9) Which of the following statements is true?A) Intermolecular forces hold the atoms in molecules together.B) Dispersion forces are generally stronger than dipole-dipole forces.C) Vapor pressure increases with temperature.D) Hydrogen bonds are stronger than covalent bonds.E) None of the above are true.

10) Define sublimation.A) The phase transition from gas to liquid.B) The phase transition from gas to solid.C) The phase transition from liquid to gas.D) The phase transition from solid to gas.E) The phase transition from liquid to solid.

11) Assign the appropriate labels to the phase diagram shown below.

A) A = gas, B = liquid, C = solid, D = critical pointB) A = solid, B = gas, C = liquid, D = supercritical fluidC) A = liquid, B = solid, C = gas, D = critical pointD) A = liquid, B = gas, C = solid, D = triple pointE) A = gas, B = solid, C = liquid, D = triple point

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12) Why is water an extraordinary substance?A) Water has strong hydrogen bonding.B) Water is the main solvent within living organisms.C) Water has a low molar mass, yet it is a liquid at room temperature.D) Water has an exceptionally high specific heat capacity.E) All of the above

13) What is the strongest type of intermolecular force present in Cl2?A) hydrogen bondingB) dipole-dipoleC) dispersionD) ion-dipoleE) none of the above

14) In the phase diagram, what is the triple point?

A) 535°C B) 184°C C) 128°C D) 114°C

15) What is the strongest type of intermolecular force present in NH2CH3?A) dipole-dipoleB) hydrogen bondingC) dispersionD) ion-dipoleE) None of the above

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16) Which substance below has the strongest intermolecular forces?A) BY2, ∆Hvap = 26.7 kJ/molB) EY3, ∆Hvap = 21.5 kJ/molC) A2X, ∆Hvap = 39.6 kJ/molD) DX2, ∆Hvap = 23.3 kJ/molE) C3X2, ∆Hvap = 36.4 kJ/mol

17) Choose the statement below that is true.A) A solution will form between two substances if the solute-solute interactions are strong enough toovercome the solvent-solvent interactions.

B) A solution will form between two substances only if the solvent-solvent interactions are weak enoughto overcome the solute-solvent interactions.

C) A solution will form between two substances if the solute-solvent interactions are of comparablestrength to the solute-solute and solvent-solvent interactions.

D) A solution will form between two substances if the solute-solvent interactions are small enough to beovercome by the solute-solute and solvent-solvent interactions.

E) None of the above are true.

18) Which of the following compounds will be most soluble in pentane (C5H12)?A) pentanol (CH3CH2CH2CH2CH2OH)B) ethyl methyl ketone (CH3CH2COCH3)C) benzene (C6H6)D) acetic acid (CH3CO2H)E) None of these compounds should be soluble in pentane.

19) Which of the following compounds is most soluble in hexane (CH3CH2CH2CH2CH2CH2CH3)?A) 1-butanol B) ethanol C) 1-propanol D) methanol E) 1-pentanol

20) Give the intermolecular force that is responsible for the solubility of ethanol in water.A) dipole-dipole forcesB) ionic forcesC) ion-dipole forcesD) dispersion forcesE) hydrogen bonding

21) Which of the following ions should have the most exothermic ∆Hhydration?

A) Na⁺ B) Sr2⁺ C) Mg2⁺ D) Ca2⁺ E) Al3⁺

22) Which of the following statements is true?A) The solubility of a solid is highly dependent on temperature.B) The solubility of a solid is not dependent on either temperature or pressure.C) The solubility of a solid is highly dependent on both pressure and temperature.D) The solubility of a solid is highly dependent on pressure.E) None of the above.

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23) Which of the following statements is true?A) The solubility of a gas in water decreases with decreasing pressure.B) The solubility of a gas in water increases with increasing pressure.C) The solubility of a gas in water decreases with increasing pressure.D) The solubility of a gas in water increases with decreasing pressure.E) None of the above statements are true.

24) Give the term for amount of solute in mole per mass of solvent in kg.A) molalityB) mole percentC) mass percentD) mole fractionE) molarity

25) Which of the following concentration units are temperature dependent?A) molalityB) mole fractionC) molarityD) mass percentE) none of the above

26) Identify the colligative property.A) boiling point elevationB) vapor pressure loweringC) freezing point depressionD) osmotic pressureE) all of the above

27) Which interaction(s) determine whether a solution will form?A) solute-solute B) solvent-solute C) solvent-solvent D) all of the above

28) A solution contains 45g of KNO3 per 100.0 g of water at 25°C. The solubility of KNO3 at this temperature is37.5 g per 100.0 g of water. The solution is ________.A) unsaturated B) saturatedC) supersaturated D) none of the above

29) Choose the aqueous solution below with the lowest freezing point. These are all solutions of nonvolatilesolutes and you should assume ideal van't Hoff factors where applicable.A) 0.075 m LiClB) 0.075 m (NH4)3PO4C) 0.075 m KNO2D) 0.075 m NaBrO4E) 0.075 m KCN

30) Which aqueous solution has the lowest boiling point?A) 0.10 m AlCl3 B) 0.10 m BaCl2 C) 0.10 m NaCl D) 0.10 m C6H12O6

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31) Which is expected to have the largest dispersion forces?A) C3H8 B) Be Cl2 C) C12H26 D) F2

32) Choose the pair of substances that are most likely to form a homogeneous solution.A) NaCl and HgB) NH3 and CH3OHC) Br2 and PF3D) C3H8 and C2H5OHE) LiF and C6H14

33) Choose the substance with the highest viscosity.A) CF4B) (CH3CH2)2COC) C2H4Cl2D) C6H14E) HOCH2CH2CH2CH2OH

34) Calculate the molality of a solution formed by dissolving 27.8 g of LiI in 500.0 mL of water.A) 0.556 m B) 0.254 m C) 0.241 m D) 0.415 m E) 0.394 m

35) What mass (in g) of NH3 must be dissolved in 475 g of methanol to make a 0.250 m solution?A) 4.94 g B) 1.90 g C) 2.02 g D) 8.42 g E) 1.19 g

36) Choose the compound that exhibits hydrogen bonding as its strongest intermolecular force.A) SCl2B) CH3OHC) CH2F2D) C2H6E) None of the above compounds exhibit hydrogen bonding.

37) Place the following substances in order of increasing boiling point.

CH3CH2OH Ar CH3OCH3

A) CH3CH2OH < CH3OCH3 < ArB) CH3CH2OH < Ar < CH3OCH3C) CH3OCH3 < Ar < CH3CH2OHD) Ar < CH3OCH3 < CH3CH2OHE) Ar < CH3CH2OH < CH3OCH3

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38) Given the following rate law, how does the rate of reaction change if the concentration of Y is doubled?

Rate = k [X][Y]2

A) The rate of reaction will decrease by a factor of 2.B) The rate of reaction will increase by a factor of 4.C) The rate of reaction will increase by a factor of 5.D) The rate of reaction will increase by a factor of 2.E) The rate of reaction will remain unchanged.

39) Which of the following substances would you predict to have the highest ∆Hvap?A) HOCH2CH2OHB) CH3CH2OHC) CH3CH2CH2CH3D) HClE) CH3Cl

40) Given the following balanced equation, determine the rate of reaction with respect to [SO2].

2 SO2(g) + O2(g) → 2 SO3(g)

A) Rate = - ∆[SO2]∆[t

B) Rate = + 12

∆[SO2]∆t

C) Rate = - 12

∆[SO2]Dt

D) Rate = + 2 ∆[SO2]∆t

E) It is not possible to determine without more information.

41) What are the units of k in the following rate law?

Rate = k[X][Y]1/2

A) M-1/2s-1 B) M-1s-1/2 C) M/s D) M1/2s-1 E) M-1s-1

42) What is the overall order of the following reaction, given the rate law?

2 X + 3 Y → 2 Z Rate = k[X]1[Y]2

A) zeroth orderB) 3rd orderC) 5th orderD) 2nd orderE) 1st order

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43) Which is expected to have the largest dispersion forces?A) C S2 B) C10H22 C) CH4 D) O2

44) Determine the rate law for the following reaction using the data provided.

NO2(g) + O3(g) → NO3(g) + O2(g)

[NO2]i (M) [O3]i (M) Initial Rate (M-1s-1)0.10 0.33 1.420.10 0.66 2.840.25 0.66 7.10

A) Rate = k[NO2][O3]2

B) Rate = k [NO2]2.5[O3]

C) Rate = k [NO2][O3]2.5

D) Rate = k [NO2]2[O3]E) Rate = k [NO2][O3]

45) Given the following balanced equation, determine the rate of reaction with respect to [O2]. If the rate of

formation of O2 is 6.94 × 10-1 M/s, what is the rate of the loss of O3?

2 O3(g) → 3 O2(g)

A) 2.08 M/s B) 4.16 M/s C) 1.04 M/s D) 0.463 M/s E) 0.231 M/s

46) Calculate the mole fraction of total ions in an aqueous solution prepared by dissolving 0.400 moles of MgCl2in 850.0 g of water.A) 0.00848 B) 0.0167 C) 0.00841 D) 0.0248 E) 0.0254

47) A solution is prepared by dissolving 98.6 g of NaCl in enough water to form 875 mL of solution. Calculatethe mass % of the solution if the density of the solution is 1.06 g/mL.A) 9.4% B) 10.6% C) 11.9% D) 11.3% E) 12.7%

48) How much energy is required to vaporize 158 g of butane (C4H10) at its boiling point, if its ∆Hvap is 24.3kJ/mol?A) 38.4 kJ B) 89.4 kJ C) 15.1 kJ D) 66.1 kJ E) 11.2 kJ

49) Choose the compound below that contains at least one polar covalent bond, but is nonpolar.A) ICl3B) SeBr4C) CF4D) HCNE) Both B and C are nonpolar and contain a polar covalent bond.

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50) Which of the following statements is true?A) The total number of molecular orbitals formed doesn't always equal the number of atomic orbitals inthe set.

B) When two atomic orbitals come together to form two molecular orbitals, one molecular orbital will belower in energy than the two separate atomic orbitals, and one molecular orbital will be higher inenergy than the separate atomic orbitals.

C) A bond order of 0 represents a stable chemical bond.D) Electrons placed in antibonding orbitals stabilize the ion/molecule.E) All of the above are true.

51) What is the mole fraction of ethanol in a solution made by dissolving 29.2 g of ethanol, C2H5OH, in 53.6 g ofwater?A) 0.213 B) 0.545 C) 0.352 D) 0.176

52) A solution is 2.25% by weight NaHCO3. How many grams of NaHCO3 are in 150.0 g of solution?A) 3.38 g B) 225 g C) 1.50 g D) 66.7 g

53) At a given temperature the vapor pressures of benzene and toluene are 183 mm Hg and 59.2 mm Hg,respectively. Calculate the total vapor pressure over a solution of benzene and toluene with Xbenzene = 0.580.A) 121 mm Hg B) 106 mm Hg C) 242 mm Hg D) 131 mm Hg

54) Which of the following solutions will have the lowest freezing point?A) 0.010 m KBr B) 0.015 m BaCl2C) 0.035 m CH3CH2OH D) 0.010 m Na2CO3

55) What is the expected freezing point of a 0.50 m solution of Li2SO4 in water? Kf for water is 1.86°C/m.A) -0.93°C B) -2.8°C C) -6.5°C D) -1.9°C

56) Consider the molecule below. Determine the hybridization at each of the 2 labeled carbons.

A) C1 = sp, C2 = sp2

B) C1 = sp2, C2 = sp3

C) C1 = sp3, C2 = sp3dD) C1 = sp2, C2 = sp3dE) C1 = sp3d, C2 = sp3d2

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57) Place the following substances in order of increasing vapor pressure at a given temperature.

NF3 NH3 BCl3

A) NH3 < BCl3 < NF3B) NH3 < NF3 < BCl3C) BCl3 < NF3 < NH3D) NF3 < NH3 < BCl3E) BCl3 < NH3 < NF3

58) The osmotic pressure of a solution formed by dissolving 25.0 mg of aspirin (C9H8O4) in 0.250 L of water at25°C is ________ atm.A) 2.45 B) 13.6 C) 0.0136 D) 1.38 E) 1.14 × 10-3

59) Which of the following compounds has the highest boiling point?A) NH3 B) H2S C) H2O D) HCl

60) List the number of sigma bonds and pi bonds in a triple bond.A) 2 sigma, 1 pi B) 2 sigma, 2 pi C) 1 sigma, 1 pi D) 1 sigma, 2 pi

NAME ____________________________________________SHORT ANSWER QUESTIONS - 4 POINTS EACH - TOTAL 32 POINTS

61) Is it possible for a molecule to be nonpolar even though it contains polar bonds? Explain your answer andgive an example.

62) Rank the following forces in order of INCREASING strength:ion-dipole, dispersion, hydrogen bonding, dipole-dipole, ion-ion

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63) Explain why the bolling point of water is so much higher than other compounds of similar molecularweight.

64) Of the following molecules which would have the highest surface tension? Explain your answer BRIEFLYby discussing the appropriate forces. CH3CH2CH3, CH3CH2F, CH2F2, CH3CH2OH, HOCH2CH2OH

65) Why does the temperature of a substance stay constant during a phase change such as vaporization?

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66) What is the weight percent of vitamin C in a solution made by dissolving 6.50 g of vitamin C, C6H8O6, in55.0 g of water? (SHOW YOUR WORK WITH UNITS FOR CREDIT)

67) The heat of vaporization of water at 100°C is 40.66 kJ/mol. Calculate the quantity of heat that isabsorbed/released when 9.00 g of steam condenses to liquid water at 100°C. (SHOW YOUR WORK WITHUNITS FOR CREDIT)

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68) Calculate the rate constant for the reaction between phenolphthalein and the OH- ion if the instantaneous rate of reactionis 2.5 x 10-5 mole per liter per second when the concentration of phenolphthalein is 0.0025 M. The reactionis firstorder in phenolpthalein. (SHOW YOUR WORK WITH UNITS FOR CREDIT)

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Answer KeyTestname: CHEM124EXAM1V1_2016

1) B2) A3) C4) C5) B6) C7) C8) A9) C10) D11) E12) E13) C14) D15) B16) C17) C18) C19) E20) E21) E22) A23) B24) A25) C26) E27) D28) C29) B30) D31) C32) B33) E34) D35) C36) B37) D38) B39) A40) C41) A42) B43) B44) E45) D46) D47) B48) D49) C

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Answer KeyTestname: CHEM124EXAM1V1_2016

50) B51) D52) A53) D54) B55) B56) B57) B58) C59) C60) D61) Yes. The polarity of a molecule depends on the molecular geometry and whether or not all of the dipoles (polar

bonds) cancel one another. If the molecular geometry causes all of the dipoles to cancel, the molecule will benonpolar. An example is CF4 where there are four polar bonds, but the dipoles sum to 0 making the moleculenonpolar.

62)63) The hydrogen bonding of the water results in a higher boiling point.64)65) The energy added to the substance is not used to raise the kinetic energy of the substance. Instead it is "used up" in

breaking the intermolecular attractions between particles to take them from a liquid (with intermolecularattractions) to a gas (with no intermolecular attractions).

66)67)68)

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