PFX1412SMR13 - Chapters 18-20

1. A gas absorbs 0.0 J of heat and then performs 56.8 J of work. What is the change in internal energy of the gas?

E) none of these

2. For a particular process, q = +20 kJ with w = 15 kJ compression. Which of the following statements is true? A) Heat flows from the system to the surroundings. B) The system does work on the surroundings. C) A ^ = 3 5 k J . D) Al l of the above are true. E) None of the above are true.

3. Which of the following compounds has the highest standard entropy per mole at 298 K? A) CH30H(/) B) CO(g) C) Si02(5) D) H20(/) E) CaC03(^)

4. The standard enthalpy of vaporization of Freon-13, CF3CI, is 15.65 kJ/mol at its normal boiling point of -82°C. What is the change of entropy for 1 mol of liquid Freon-13 when it vaporizes at its normal boiling point? A) 81.9 J/K B) -0.191 J/K C) -1.91 X 102 J/K D) 8.19 X 10-2 J/K E) 2.99 X 103 J/K

A) B) C) D)

16.8 J 56.4 J 96.8 J -56.8 J

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5. The standard enthalpy of vaporization of ether is 26.5 kJ/mol at its normal boiling point, 34.5°C. What is the standard change in entropy for the vaporization of ether at its normal boiling point? A) -26.5 J/(mol • K) B) 0.768 J/(mol • K) C) 768 J/(mol • K) D) 86.1 J/(moI • K) E) 0.0861 J/(mol • K)

6. In which reaction is AS° expected to be positive? A) I2(g)->l2(5) B) H20(7) ^H20(5) C) CH30H(g) + K 02(g) -> C02(g) + 2H20(1) D) 202(g)+ 2SO(g)-^2S03(g) E) none of these

7. For which of the following reactions is AS° at 25°C closest to zero? A) H2(g) + l2(5)->2HI(g) B) C2H4(g) + Br2(/) C2H4Br2(/) C) N2(g) +02(g) ^ 2 N 0 ( g ) D) 2NO(g) + 02(g) 2N02(g) E) CH3CH0(g) + 5/202(g) ^ 2C02(g) + 2H20(g)

8. For the process B r 2 ( 0 2 B r ( g ) , A) AH is + and AS is + for the reaction. B) AH is - and AS is- for the reaction. C) AH is + and AS is - for the reaction. D) AH is - and AS is + for the reaction. E) AG is + for all temperatures.

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9. What is AS° at 298 K for the following reaction? 203(g) ^ 302(g) Substanc S° HKmol • K)) at 298

e K 02(g) 205.0 03(g) 238.8

A) +137.4 J/K B) -137.4 J/K C) +33.8 J/K D) -33.8 J/K E) +443.8 J/K

10. What is AG° at 298 K for the following reaction? I2(g) + Cl2(g) 2ICl(g); AH° = -27.4 kJ; AS° = 11.5 J/K at 298 K A) -24.0 kJ B) -3.45 X lO^kJ C) -30.8 kJ D) 3.45 X lO^kJ E) 30.8 kJ

11. A 0.0619 M solution of a particular monoprotic weak acid, HA, has a pH of 4.90 at 298 K. What is AG° for the following equilibrium?

HA(a^) + H20(/) mO^aq) + A-(aq) A) 6.89 kJ B) 49.0 kJ C) 21.1 kJ D) 27.9 kJ E) 484 kJ

12. For a reaction system that is at equilibrium, which of the following must always be true? A) AG = 0 B) AH=0 C) AU=0 D) AS = 0 E) q = 0

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13. The standard free energy of formation of nitric oxide, NO, at 1000. K (roughly the temperature in an automobile engine during ignition) is 78.0 kJ/mol. Calculate the equilibrium constant for the reaction

N2(g) + 0 , ( g ) ^ 2N0(g) at 1000. K. (Note: The listed free energy value is for one (1) mole of NO(g). The

reaction equation shows 2-moles of NO(g). Therefore, A G must be doubled in

equation containing Keq... i.e., 2( A G ) = -RT InK^q and solve for Keq.) A) 1.56 X 105 B) 8.42 X 10-5 C) -14.7 D) 7.10 X 10-' E) 0.948

14. Consider the following hypothetical reaction (at 319.0 K). Standard free energies, in kJ/mol, are given in parentheses.

A B + C AG° = ? (-32.2) (207.8) (-237.0)

What is the value of the equilibrium constant for the reaction at 319.0 K? (Note: No

need to use a multiple of A G in this problem as determination of A G is a per mole value as calculated.) A) 0.32 B) 1.0 C) 6.0 X 104 D) 273 E) 0.41

15. For which of the following reactions is A/ / equal to At/? {Note: AU is 'Internal Energy'.) A) 2H202(/) 2H2O(0 + 02(g) B) BaO(5) + S03(g) ^ BaS04(5) C) 2N0(g) +02(g) ^2N02(g) D) H2(g) + Cl2 (g)^2HCl(g) E) 2KC103(^) ^ 2KC1(^) + 302(g)

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16. According to the following thermochemical equation, i f 422.3 g of NO2 is produced, how much heat is released at constant pressure? (Hint: Covert grams produced to moles and solve by proportional ratio.) 2N0(g) + 02(g) 2N02(g); = -114.4 kJ A) 1.050 X lO^kJ B) 12.46 kJ C) 5.251 X 102 kJ D) 114.4kJ E) 4.831 X lO^kJ

17. How much heat is gained by iron when 12.0 g of iron is warmed from 14.4°C to 79.5°C? The specific heat of iron is 0.449 J/(g • °C). A) 7.76 X 10' J B) 4.28 X 102 J C) 29.2 J D) 3.51 X 102 J E) 35.7 J

18. A 140.0-g sample of metal at 80.0°C is added to 140.0 g of H20(/) at 22.0°C in an insulated container. The temperature rises to 23.9°C. Neglecting the heat capacity of the container, what is the specific heat of the metal? The specific heat of H20(/) is 4.18 J/(g • °C). A) 29.2 J/(g • °C) B) 0.143 J/(g • °C) C) -0.143 J/(g • °C) D) 122 J/(g • °C) E) 4 .18J / (g-°C)

19. How much heat must be applied to a 38.3-g sample of nickel (specific heat (c) = 0.443 J/(g • °C)) in order to raise its temperature from 22.8°C to 378.8°C? A) 1.58 X 102 J B) 6.43 X 103 J C) 3.87 X 102 J D) 1.36 X 10^ J E) 6.04 X 103 J

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20. In the following reaction, which species is oxidized? 3CS2S(5) + 8H^(fl^) + 2N03-{aq) 6Cs\aq) + 3S(s) + 2N0(g) + 4H2O A) CS2S B) C) NO3-D) NO E) Cs+

21. For the reaction that occurs in a lead storage battery, Pb(5) + Pb02(5) + IH^iaq) + 2HS04-(fl9) ^ 2PbS04(5) + 2H20(/) the oxidizing agent is A) Pb. B) Pb02. C) H+. D) HSO4-. E) PbS04.

22. When the following oxidation-reduction reaction is balanced, what is the sum of the coefficients?

P4 + CI2 -> PCI5 A) 10 B) 15 C) 16 D) 20 E) 25

23. The following reaction occurs in basic solution. What is the sum of the lowest whole-number coefficients in the balanced equation?

Mn04- + NH3 ^ NO3- + Mn02 A) 9 B) 18 ^ \ C) 12 D) 23 E) 29

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24. The following change occurs in acidic solution: S^-(aq) + CnOi^-iaq) S(s) + Cr'^aq)

In the balanced equation, for every mole of Cr2072"that reacts, mol of are consumed. A) 5 B) 7 C) 8 D) 10 E) 14

25. When the following oxidation-reduction reaction in acidic solution is balanced, what is the lowest whole-number coefficient for ^a^(aq)'? Na(5) + Cu^^aq) -> Na+(fl9) + Cu(5) A) 1 B) 2 C) 3 D) 4 E) 5

26. When the following oxidation-reduction reaction in acidic solution is balanced, what is the lowest whole-number coefficient for H" , and on which side of the balanced equation should it appear? Cr207^-(aq) + CU20(aq) Cr^^aq) + UCOOUiaq) A) 1, reactant side B) 2, product side C) 6, product side D) 8, reactant side E) 14, reactant side

27. Which of the following statements is true for a voltaic (galvanic) cell? A) The electron flow is from the positive electrode to the negative electrode. B) The electron flow is from the anode to the cathode. C) The electron flow is from the oxidizing agent to the reducing agent through an

external circuit. D) The electron flow is from the negative cathode to the positive anode. E) The electron flow is through the salt bridge.

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28. A strip of iron is placed in a 1 M solution of iron(II) sulfate, and a strip of copper is placed in a 1 M solution of copper(II) chloride. The two solutions are connected with a salt bridge, and the two metals are connected to a voltmeter. With the two electrodes connected together, how do the CI" ions move?

Reduction Half-Reaction E° (V)

Fe2+(ag) + 2e- VQ{S) "^-"^^

C\x^\aq) + 2e- ^ Cn{s) ^'^"^ A) through the external circuit from Cu to Fe B) through the salt bridge from the Cu half-cell to the Fe half-cell C) in random fashion D) in the direction opposite to the movement of the sulfate ions E) together with the Cu^^ ions to form an insoluble precipitate

29. £'°ceii = 1.66 V for the following cell reaction: VA{S) + 30\l-{aq) + 3H2O(0 -> PH3(g) + 3H2P02-(a^) The oxidizing and reducing agents are, respectively, A) P4andOH-. B) 0H-andP4. C) H20andP4. D) P4andH20. E) P4andP4.

30. A strip of iron is placed in a 1 M solution of iron(II) sulfate, and a strip of copper is placed in a 1 M solution of copper(II) chloride. The two solutions are connected with a salt bridge, and the two metals are connected by a wire.

Reduction Half-Reaction E° (V)

VQ^\aq) + 2e- Fe(^) "^-"^^ Cu^+Ca^) + 2e- Cu(5) ^"^^

Which of the following takes place? A) The Fe(II) concentration of the iron half-cell decreases. B) Chlorine is produced at the iron electrode. C) Chlorine is produced at the copper electrode. D) Copper atoms deposit at the cathode. E) Sulfur deposits at the iron electrode.

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31. Which of the following statements is true concerning half-cell I I of the voltaic cell shown below?

A) B) C) D) E)

I n Cu " migrates away from the Cu anode. Cu " migrates toward the Cu anode. Cu^^ migrates away from the Cu cathode. Cu"* migrates toward the Cu cathode. There is no net migration of Cu^^ toward or away from the Cu electrode.

32. According to the following cell notation, which species is undergoing oxidation? Cu I Cu^^iaq) || Mn02(5) | Mn^^{aq) | Pt A) Cu B) Cu2+ C) Pt D) Mn02 E) Mn^^

33. In the following electrochemical cell, what is the oxidizing agent? Ni(5) I N i ^ V g ) II Fe^^iaq), Fe^^(aq) | Pt(5) A) Pt B) N i C) Ni2^ D) Fe2+ E) Fe3+

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34. In the following electrochemical cell, what is the reducing agent? Zn(5) I Zx^\aq) \\, Fe^+Ca^) | Pt(5) A) Pt B) Zn C) Zn2+ D) Fe2+ E) Fe ^

35. A zinc-copper voltaic cell is represented as follows: Zn(^) I Zn2^(1.0 M) \\O M) \(5) Which of the following statements is false? A) The mass of the zinc electrode decreases during discharge. B) The copper electrode is the anode. C) Electrons flow through the external circuit from the zinc electrode to the

electrode. D) Reduction occurs at the copper electrode during discharge. E) The concentration of Cu " decreases during discharge.

36. What is the cell reaction for the following voltaic cell? Cr(5) I C^\aq) \\) | Br2(g) I Pt(5)

A) Cr(5) + T&riaq) -— - Br2(g) + Cr3-(a^)

B) lC^\aq) + 6Br(a^) ^ 2Cr(5) + 3Br2(g)

C) Cr(5) + 3Br2(g) — Cr3+( ) + 2Br-(fl^)

D) 2Cr(5) + 3Br2(g) - lQ^\aq) + 6BrXa^)

E) Cr(5) + C^^iaq) ^ - ^r{aq) + Br2(g)

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A) Zn(5) I Zn2\aq) || Cu(s) \B) Zn{s) I Zn^^iaq) \\ | Cu(^) C) Zn^^iaq) \ || Cuis) \D) Zn^\aq) \ || Cu^+C^^) | Cu(^) E) Zn(5) I Cu(5) II Zn^^iaq) \

n

38. Consider the following standard electrode potentials:

Ag+(a^) + e- Agis); E° = 0.80 V

Mn^Xaq) + 2e- Mn{s); £° - -1.18 V Which of the following statements is false concerning the electrochemical cell given below? Mn(5) I Mxi^^aq) \\ \A) Under standard-state conditions, the cell potential is 1.98 V. B) The anode half-cell reaction is Mn{s) Mn^^(aq) + 2Q~. C) The cell potential decreases with time. D) The reducing agent is Ag(5). E) The oxidizing agent is Ag^{aq).

39. In a table of standard reduction potentials, the strongest oxidizing agents are the species in the half-reactions with the E° values.

A) oxidized, most negative B) reduced, most negative C) oxidized, most positive D) reduced, most positive E) none of these

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40. Which of the following statements is true about a voltaic cell for which ^"ceii = 1.00 V? A) I t h a s A G ° > 0 . B) The system is at equilibrium. C) It has ^ = 1 . D) The cathode is at a higher energy than the anode. E) The reaction is spontaneous.

41. What is the copper(II)-ion concentration at 25°C in the cell Znis) \ M) \\ Cv?''{aq) I Cu(5) i f the measured cell potential is 1.01 V? The standard cell potential is 1.10 V. A) 0.994 M B) 0.000911 M C) 0.0302 M D) 0.988 M E) LOOM

42. What is £ o f t h e following cell reaction at 25°C? £°ceii = 0.460 V. Cu(5) I Cu2+(0.010 M) II Ag\Q.\6M) \A) 0.282 V B) 0.488 V C) 0.460 V D) 0.472 V E) 0.496 V

43. Cathodic protection results when A) iron is attached to a more active metal. B) iron is amalgamated with mercury. C) iron is tin-plated for use as a tin can. D) iron is painted to protect it from corrosion. E) iron is made amphoteric.

44. Molten magnesium chloride is electrolyzed using inert electrodes and reactions represented by the following two half-reactions: 2 C l - ( 0 ^ C b ( g ) + 2e-Mg2^(/) + 2e-->Mg(5) Concerning this electrolysis, which of the following statements is true? A) Oxidation occurs at the cathode. B) Mg2^ ions are reduced at the anode. C) Electrons pass through the metallic part of the circuit from Mg " ions to the CI" ion. D) CI" ions are reducing agents. E) The anions in the electrolyte undergo reduction.

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45. What is the half-reaction that occurs at the potassium iodide solution?

Reduction Half-Reaction

K'iaq) + e- Kis)

Mg^^iaq) + 2e- Mgis)

2H20(/) + 2e- H2(g) + 20H-(a^)

2H+(a^) + 2e- H2(g)

12(5) + 2e- 2I-(a^)

02(g) + m-'iaq) + 4e- 2H20(/) A) K+(ag) + e - ^ K(5) B) K ( 5 ) ^ K + + e-C) l2(a^) + 2 e - ^ 2I-(a^) D) H20(/) '/202(g) + 2U\aq) + 2e" E) 2H2O(0 + 2e- ^ H2(g) + 20H-(a9)

46. How many faradays are required to convert a mole of NO3" ions to NH4' ions? A) 4 B) 5 C) 6 D) 7 E) 8

47. I f an electrolysis plant operates its electrolytic cells at a total current of 1.6 x 10 A, how long wil l it take to produce one metric ton (one million grams) of Mg(^) from seawater containing Mg " ? (1 faraday = 96,485 coulombs) A) 1.4 h B) 1.4 days C) 41 min D) 0.7 h E) 0.34 year

48. ''"Ar can be prepared by electron capture from A) 36C1. B) C) 4iAr. D) 40Ca. E)

cathode durmg electrolysis of an aqueous

E°(V) -2.93

-2.37

-0.83

0.00

0.54

1.23

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49. When '°3pd undergoes electron capture, what is the product nucHde? A) 'o^Ag B) " ' Cd C) 'o^Ag D) 'O^Rh E) '«'Rh

50. When ^^Na undergoes beta emission, what is the product nuclide? A) 25Ne B) 24Na C) 24Ne D) 24Mg E) 25Mg

51. When the radioactive nuclide '^N undergoes positron emission, what is the product nuclide? A) " N B) '"O C) '^c D) E)

52. When the radioactive nuclide '''^At undergoes alpha emission, what is the product nuclide? A) '^^Bi B) '^^Bi C) ' ^Fr D) 203Fr E) ' ^Rn

53. What is the abbreviated notation for the following nuclear bombardment reaction? f3Al + ^He '"P+on

A) f3Al(a,A)fsP

B) f3Al(n ,a)^°P

C) f3Al(a, n)^°P

D) f 3 A l ( n , d ) - P

E) f3Al(a,p)f3P

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54. A particular nuclear bombardment reaction is represented by the abbreviated notation (n, a)X. What is the identity of the nuclide X?

55. A Geiger counter measures radiation by detecting A) electrons released when gas atoms are ionized by the radiation. B) alpha and beta particles as they strike a detector window. C) flashes of light emitted from a phosphor affected by radiation. D) the increase in temperature when a gas is struck by radiation. E) cations produced from radiation colliding with phosphor gases.

56. A scintillation counter measures radiation by detecting A) electrons released when gas atoms are ionized by the radiation. B) alpha and beta particles as they strike a detector window. C) flashes of light emitted from a phosphor affected by radiation. D) the increase in temperature when a gas is struck by radiation. E) cations produced from radiation colliding with phosphor gases.

57. As a radioactive isotope decays, its rate constant A) doubles. B) halves. C) decreases. D) increases. E) remains the same.

58. The rate constant for the decay of joCa is 4.228 x 10^ / day. What is the half-life of

-Ca? A) 81.95 days B) 163.9 days C) 327.8 days D) 409.8 days E) none of these

A)

B)

C)

D)

E)

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59. Strontium-90 is produced in nuclear explosions. It can replace calcium in the bone. The half-life of^^Sr is 27.7 years. What is the decay constant for ^°Sr? A) 0.0125/year B) 0.0250/year C) 0.0375/year D) 0.0425/year E) 0.0450/year

60. The half-life of the radioactive nuclide ^^Br is 2.9 min. What is the activity of a 9.0-^g sample of^W The molar mass of ^Br is 84.916 g/mol. (1 Ci = 3.700 x 10'« disintegrations/s) A) 4.1 X 105 Ci B) 6.1 X lO-'oCi C) 9.9 X 103 Ci D) 7.1 X 10-'^ Ci E) 6 .9x l03Ci

61. The half-life of the radioisotope '^^Eu is 0.77 h. How much time is required for a 160.0-g sample of '^^Eu to decay to 2.53 g? A) 3.0 h B) 4.0 h C) 6.0 h D) 2.0 h E) 4.6 h

62. The half-life of phosphorus-33 is 25 days. How much of a 128-g sample wil l remain after 140 days? A) 16 g B) 8.0 g C) 4.0 g D) 2.6 g E) 1.0 g

63. A sample of wood from an Egyptian mummy case gives a '''C count of 9.0 cpm/gC (counts per minute per gram of carbon). How old is the wood? (The initial decay rate of "Cis 15.3 cpm/g C, and its half-life is 5730 years.) A) 2194 years B) 6887 years C) 4387 years D) 5437 years E) none of these

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64. How much energy is released when 2.00 metric tons of Ha gas undergoes nuclear fusion? (1 metric ton= 1000 kg, c = 3.00 x 10« m/s, 1 amu = 1.66054 x IQ-^' kg) 2H + 2H -> 3He + 'n

Particle Mass (amu) •n 1.008665

2H 2.01400

3He 3.01603

A) 2.95 X lO 'M B) 6.77 X lO-'» J C) 5.39 X 10 4 J D) 1.48 X 1017 J E) 1.07 x l O ^ ' J

65. Relative to the sum of the masses of its constituent nucleons (neutrons + protons), the mass of a nucleus is A) always greater. B) always the same. C) always smaller. D) sometimes the same and sometimes smaller. E) sometimes greater and sometimes smaller.

66. What is the mass defect of 'JBe ? Particle Mass (amu)

'^Be 11-0216

|p 1.00728

iji 1.00867

0.00055

A) -1.685 amu B) -0.1707 amu C) -0.1055 amu D) -0.0704 amu E) ^.1051 amu

67. Enriched uranium is uranium that has a greater proportion of A) deuterons. B) lead-207. C) lead-208. D) uranium-235. E) uranium-238.

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. It is possible that the world's energy problem could be solved by making use of the fusion reaction of deuterium and tritium. Which of the following reaction equations corresponds to that process?

A) ^He+ on

B) in+]H -> ^He+<;n

C) ; H -> ' H + °n

D) In ^ 2

E) ^ 2 ; H + 3 >

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Answer Key

1. D 2. C 3. B 4. A 5. D 6. E 7. C 8. A 9. A

10. C 11. B 12. A 13. D 14. A 15. D 16. C 17. D 18. B 19. E 20. A 21. B 22. B 23. E 24. E 25. B 26. D 27. B 28. B 29. E 30. D 31. D 32. A 33. E 34. B 35. B 36. D 37. B 38. D 39. C 40. A 41. B 42. D 43. A 44. D

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45. E 46. E 47. A 48. B 49. D 50. E 51. C 52. B 53. C 54. E 55. A 56. C 57. E 58. B 59. B 60. E 61. E 62. D 63. C 64. D 65. C 66. D 67. D 68. B