University of South Florida

CHM 2046

Chapter 17 Free Energy and Thermodynamics

1)Which of the following statements is TRUE?

1. 1. There is a "heat tax" for every energy transaction.
   2. A spontaneous reaction is always a fast reaction.
   3. The entropy of a system always decreases for a spontaneous process.
   4. Perpetual motion machines are a possibility in the near future.
   5. None of the above are true.

2. In which of the following processes does the molecules become more orderly?
   1. water freezing
   2. ice melting
   3. water evaporating
   4. salt dissolving in water
   5. dry ice subliming

3. Identify the change in state that does not have an increase in entropy.
   1. water freezing
   2. water boiling
   3. ice melting
   4. dry ice subliming
   5. water evaporating

4. For which process is ΔS negative?

1. evaporation of 1 mol of CCl4(l)
2. mixing 5 mL ethanol with 25 mL water
3. compressing 1 mol Ne at constant temperature from 1.5 atm to 0.5 atm
4. raising the temperature of 100 g Cu from 275 K to 295 K
5. grinding a large crystal of KCl to powder

5. In which reaction is ΔS° expected to be positive?

A) I2(g) → I2(s)

B) H2O(1) →H2O(s)

C) CH3OH(g) + (3/2)O2(g) → CO2(g) + 2H2O(l)

D) 2O2(g) + 2SO(g) → 2SO3(g)

E) none of these

6. Which statement is true?
   1. All real processes are irreversible.
   2. A thermodynamically reversible process takes place infinitely fast.
   3. In a reversible process, the state functions of the system are always much greater than those of the surroundings.
   4. There is always more heat given off to the surroundings in a reversible process than in an unharnessed one.
   5. All statements (a–d) are true.

7. Which statement below is not upheld by the second law of thermodynamics?
   1. The change of entropy of the universe is always positive.
   2. The entropy of a perfect crystal at 0 K is zero. (THIS IS THIRD LAW)
   3. Machines always waste some energy.

1. 4. A machine is never 100% efficient.
   5. All of these

8. The heat of vaporization for 1.0 mole of water at 100.o C and 1.0 atm is 40.62 kJ/mol. Calculate ΔS for the process H O(l) H O(g) 2 2 → at 100.o C.

1. 109 J/K mol
2. –109 J/K mol
3. 406 J/K mol
4. –406 J/K mol
5. none of these

9. For a spontaneous exothermic process, which of the following must be true?

1. ΔG must be positive.
2. ΔS must be positive.
3. ΔS must be negative.
4. Two of the above must be true.
5. None of the above (a-c) must be true.

10. For a particular chemical reaction ΔH = 5.5 kJ and ΔS = –25 J/K Under what temperature condition is the reaction spontaneous?

1. When T < –220 K.
2. When T < 220 K.
3. The reaction is spontaneous at all temperatures.
4. The reaction is not spontaneous at any temperature.
5. When T > 220 K.

11. In which case must a reaction be spontaneous at all temperatures?

1. ΔH is positive, ΔS is positive.
2. ΔH = 0, ΔS is negative.
3. ΔS = 0, ΔH is positive.
4. ΔH is negative, ΔS is positive.
5. none of these

12. Consider the dissociation of hydrogen: H2(g) ? 2H(g)

One would expect that this reaction:

1. will be spontaneous at any temperature.
2. will be spontaneous at high temperatures.
3. will be spontaneous at low temperatures.
4. will not be spontaneous at any temperature.
5. will never happen.

13. Which of the following processes have a ΔS > 0?
    1. CH3OH(l) → CH3OH(s)

B) N2(g) + 3 H2(g) → 2 NH3(g)

C) CH4(g) + H2O (g) → CO(g) + 3 H2(g)

4. Na2CO3(s) + H2O(g) + CO2(g) → 2 NaHCO3(s)
5. All of the above processes have a DS > 0.

14. Which of the following processes have a ΔS > 0?
    1. 2 NH3(g) + CO2(g) → NH2CONH2(aq) + H2O(l)
    2. lithium fluoride forms from its elements
    3. 2 HBr(g) → H2(g) + Br2(l)
    4. sodium chloride dissolves in pure water.
    5. All of the above processes have a DS > 0.

15. Which of the following processes have a ΔS < 0?
    1. water freezes
    2. isopropyl alcohol condenses
    3. methanol (g, at 555 K) → methanol (g, at 400 K)
    4. carbon dioxide (g) → carbon dioxide (s)
    5. All of the above processes have a ΔS < 0.

16. Which of the following processes shows a decrease in entropy of the system?

A) 2 NO(g) + O2(g) → 2 NO2(g)

2. COCl2(g) → CO(g) + Cl2(g)
3. CH3OH(l) → CO(g) + 2H2(g)
4. NaClO3(s) →Na+(aq) + ClO3-(aq)
5. None of the above will show a decrease in entropy.

17. Which of the following statements is TRUE?
    1. Entropy is not a state function.
    2. Endothermic processes decrease the entropy of the surroundings, at constant T and P.
    3. Endothermic processes are never spontaneous.
    4. Exothermic processes are always spontaneous.
    5. None of the above are true.

18. What is the sign of ΔS_univ for a biological system?
    1. positive
    2. negative
    3. zero
    4. It depends on the biological system.

19. Identify the change in state that does not have an increase in entropy.
    1. Water freezing
    2. Water boiling
    3. Ice melting
    4. Dry ice subliming
    5. Water evaporating

20. For the reaction 2SO2(g) + O2(g) → 2SO3(g), ΔH° and ΔS° are both negative at 298 K, and the process is spontaneous at 298 K. Which of the following statements must also be true?

1. ΔG is positive for the reaction at 298 K.
2. The change in entropy is the driving force of the reaction.
3. ΔG is temperature independent.
4. The direction of the reaction may be reversed at high temperatures.

5. At high temperature, ΔH becomes positive.

21. For the reaction 2SO2(g) + O2(g) → 2SO3(g), ΔH° and ΔS° are both negative at 298 K, and the process is spontaneous at 298 K. Which of the following statements must also be true?

1. Change in entropy is the driving force for the spontaneity of the reaction at 298K
2. ΔG is positive for the reaction at 298 K.
3. The reaction may become non-spontaneous at high temperatures
4. ΔG is not dependent on temperature for this reaction.
5. At high temperature, ΔH becomes positive.

22. Consider the following reaction at constant P. Use the information here to determine the value of ΔSsurr at 298 K. Predict whether or not this reaction will be spontaneous  at this temperature.

N2(g) + 2 O2(g) → 2 NO2(g)                         ΔH = +66.4 kJ

1. 1. ΔSsurr = +223 J/K, reaction is spontaneous
   2. ΔSsurr = -223 J/K, reaction is not spontaneous
   3. ΔSsurr = -66.4 J/K, reaction is spontaneous
   4. ΔSsurr = +66.4 kJ/K, reaction is not spontaneous
   5. ΔSsurr = -66.4 J/K, it is not possible to predict the spontaneity of this reaction without more information.

23. Consider the following reaction at constant P. Use the information here to determine the value of ΔSsurr at 355 K. Predict whether or not this reaction will be spontaneous at this temperature.

2 NO(g) + O2(g) → 2 NO2(g)                        ΔH = -114 kJ

1. 1. ΔSsurr = +114 kJ/K, reaction is spontaneous
   2. ΔSsurr = +114 kJ/K, reaction is not spontaneous
   3. ΔSsurr = +321 J/K, reaction is spontaneous
   4. ΔSsurr = -321 J/K, reaction is not spontaneous
   5. ΔSsurr = +321 J/K, it is not possible to predict the spontaneity of this reaction without more information.

24. Consider the following reaction at constant P. Use the information here to determine the value of ΔSsurr at 398 K. Predict whether or not this reaction will be spontaneous at this temperature.

4 NH3(g) + 3 O2(g) → 2 N2(g) + 6 H2O(g) ΔH = -1267 kJ

1. 1. ΔSsurr = +12.67 kJ/K, reaction is not spontaneous
   2. ΔSsurr = -12.67 kJ/K, reaction is spontaneous
   3. ΔSsurr = +50.4 kJ/K, reaction is not spontaneous
   4. ΔSsurr = +3.18 kJ/K, reaction is spontaneous
   5. ΔSsurr = -3.18 kJ/K, it is not possible to predict the spontaneity of this reaction without more information.

25. Which of the following relationships is correct at constant T and P?
    1. ΔG is proportional to -ΔSuniv
    2. ΔG > 0 represents a spontaneous process
    3. ΔG > 0 represents an increase in kinetic energy
    4. ΔG < 0 represents a nonspontaneous process.
    5. All of the above are correct.

26. Consider a reaction that has a positive ΔH and a positive ΔS. Which of the following statements is TRUE?
    1. This reaction will be spontaneous only at high temperatures.
    2. This reaction will be spontaneous at all temperatures.
    3. This reaction will be nonspontaneous at all temperatures.
    4. This reaction will be nonspontaneous only at high temperatures.
    5. It is not possible to determine without more information.

27. Consider a reaction that has a positive ΔH and a positive ΔS. Which of the following statements is TRUE?
    1. This reaction will be spontaneous only at low temperatures.
    2. This reaction will be spontaneous at all temperatures.
    3. This reaction will be nonspontaneous at all temperatures.
    4. This reaction will be nonspontaneous only at low temperatures.
    5. It is not possible to determine without more information.

28. Consider a reaction that has a negative ΔH and a positive ΔS. Which of the following statements is TRUE?
    1. This reaction will be spontaneous only at high temperatures.
    2. This reaction will be spontaneous at all temperatures.
    3. This reaction will be nonspontaneous at all temperatures.
    4. This reaction will be nonspontaneous only at high temperatures.
    5. It is not possible to determine without more information.

29. Consider a reaction that has a positive ΔH and a negative ΔS. Which of the following statements is TRUE?
    1. This reaction will be spontaneous only at high temperatures.
    2. This reaction will be spontaneous at all temperatures.
    3. This reaction will be nonspontaneous at all temperatures.
    4. This reaction will be nonspontaneous only at high temperatures.
    5. It is not possible to determine without more information.

30. Consider a reaction that has a negative ΔH and a negative ΔS. Which of the following statements is TRUE?
    1. This reaction will be spontaneous only at high temperatures.
    2. This reaction will be spontaneous at all temperatures.
    3. This reaction will be nonspontaneous at all temperatures.
    4. This reaction will be nonspontaneous only at high temperatures.
    5. It is not possible to determine without more information.

31. For a reaction that has an equilibrium constant of 6 × 10^9, which of the following statements must be true?

1. ΔS° is positive.
2. ΔG° is negative.
3. ΔG° is positive.
4. ΔH° is negative.
5. ΔH° is positive

32. For a reaction that has an equilibrium constant of 7 × 10^-3, which of the following statements must be true?

1. ΔS° is positive.
2. ΔG° is negative.
3. ΔG° is positive.
4. ΔH° is negative.
5. ΔH° is positive

33. Consider a reaction that has a negative ΔH and a negative ΔS. Which of the following statements is TRUE?
    1. This reaction will be spontaneous only at low temperatures.

1. 2. This reaction will be spontaneous at all temperatures.
   3. This reaction will be nonspontaneous at all temperatures.
   4. This reaction will be nonspontaneous only at low temperatures.
   5. It is not possible to determine without more information.

34. For the following example, identify the following.

2 N2O (g)  → 2 N2(g) + O2(g)

1. 1. a negative ΔH and a negative ΔS
   2. a positive ΔH and a negative ΔS
   3. a negative ΔH and a positive ΔS
   4. a positive ΔH and a positive ΔS
   5. It is not possible to determine without more information.

35. Above what temperature does the following reaction become nonspontaneous?

2 H2S(g) + 3 O2(g)  → 2 SO2(g) + 2 H2O(g)                             ΔH =  -1036 kJ; ΔS = -153.2 J/K

A) 6.762 × 103 K

B) 158.7 K

3. 298 K
4. This reaction is nonspontaneous at all temperatures.
5. This reaction is spontaneous at all temperatures.

36. Above what temperature does the following reaction become nonspontaneous? FeO(s) + CO(g)  → CO2(g) + Fe(s)                                          ΔH = -11.0 kJ; ΔS = -17.4 J/K
    1. 632 K
    2. 298 K
    3. 191 K
    4. This reaction is nonspontaneous at all temperatures.
    5. This reaction is spontaneous at all temperatures.

37. Below what temperature does the following reaction become nonspontaneous?

2 HNO3(aq) + NO(g) → 3 NO2(g) + H2O(l)                             ΔH = +136.5 kJ; ΔS = +287.5 J/K A) 39.2 K

2. 151 K
3. 475 K
4. This reaction is nonspontaneous at all temperatures.
5. This reaction is spontaneous at all temperatures.

38. Which of the following statements is TRUE?
    1. Entropy is an extensive property.
    2. Entropy is not temperature dependent.
    3. Exothermic processes decrease the entropy of the surroundings.
    4. ΔSuniverse is always greater than zero for a nonspontaneous process.
    5. None of the above are true.

39. Place the following in order of increasing molar entropy at 298 K.

CO2            C3H8          SO

39. 1. CO2 < C3H8 < SO
    2. C3H8 < CO2 < SO
    3. SO < CO2 < C3H8
    4. C3H8 < SO < CO2
    5. CO2 < SO < C3H8
40. Place the following in order of increasing entropy at 298 K. Ne                   Xe              He              Ar              Kr
    1. He <  Kr  < Ne < Ar  < Xe
    2. Xe < Kr  < Ar <  Ne <  He
    3. Ar <  He < Ar < Ne <  Kr
    4. Ar < Ne < Xe < Kr < He
    5. He < Ne < Ar < Kr < Xe

41. Place the following in order of decreasing molar entropy at 298 K. HCl                    N2H4         Ar

1. Ar > N2H4 > HCl
2. Ar > HCl > N2H4
3. N2H4 > Ar > HCl
4. N2H4 > HCl > Ar
5. HCl > N2H4 > Ar

42. Place the following in order of increasing molar entropy at 298 K. NOCO                    SO
    1. NO < CO < SO
    2. SO < CO < NO
    3. SO < NO < CO
    4. CO < SO < NO
    5. CO < NO < SO

43. Place the following in order of decreasing molar entropy at 298 K. H2 Cl2                    F2
    1. H2 > Cl2 > F2
    2. Cl2 > H2 >  F2
    3. F2 > Cl2 >  H2
    4. H2 > F2 >  Cl2
    5. Cl2 > F2 > H2
44. Place the following in order of increasing standard molar entropy. H2O (l) H2O (g) H2O (s)

44. 1. H2O (g) < H2O (l) < H2O (s)
    2. H2O (s) < H2O (l) < H2O (g)
    3. H2O (g)  < H2O (s) <  H2O (l)
    4. H2O (l) < H2O (s) <  H2O (g)
    5. H2O (s) < H2O (g) <  H2O (l)
45. Place the following in order of decreasing standard molar entropy. NaCl(s)                        Na3PO4 (aq) NaCl (aq)
    1. NaCl(s) > NaCl (aq) > Na3PO4 (aq)
    2. NaCl (aq) > NaCl(s) > Na3PO4 (aq)
    3. Na3PO4 (aq)  > NaCl (aq) > NaCl(s)
    4. NaCl(s) > Na3PO4 (aq) > NaCl (aq)
    5. NaCl (aq) > Na3PO4 (aq) > NaCl(s)
46. Place the following in order of decreasing standard molar entropy. N2O4 (g)                     NO (g)         NO2 (g)
    1. N2O4 > NO2 > NO
    2. NO > NO2 > N2O4
    3. N2O4 > NO > NO2
    4. NO > N2O4 > NO2
    5. NO2 > NO > N2O4
47. Identify the compound that is NOT an allotrope of carbon.
    1. Diamond.
    2. Dry ice.
    3. Graphite.
    4. Charcoal.
    5. Buckyball.

48. Calculate ΔS°rxn for the following reaction. The S° for each species is shown below the reaction.

C2H2(g) + H2(g) → C2H4(g) S°(J/mol?K)        200.9         130.7         219.3

A) +112.3 J/K

B) +550.9 J/K

C) -112.3 J/K

D) +337.1 J/K

E) -550.9 J/K

49. Calculate ΔS°rxn for the following reaction. The S? for each species is shown below the reaction.

C2H2(g) + 2 H2(g) → C2H6(g) S°(J/mol?K)        200.9             130.7               229.2

A) +303.3 J/K

B) +560.8 J/K

C) -102.4 J/K

D) -233.1 J/K

E) 229.2 J/K

50. Calculate ΔS°rxn for the following reaction. The S° for each species is shown below the reaction.

4 NH3(g) + 5 O2(g)  →  4 NO(g) + 6 H2O(g)

S°(J/mol?K)        192.8             205.2                     210.8               188.8

A) +287.4 J/K

B) -401.2 J/K

C) +160.0 J/K

D) -336.6 J/K

E) +178.8 J/K

51. Calculate ΔS°rxn for the following reaction. The S° for each species is shown below the reaction.

N2H4(l) + H2(g) → 2 NH3(g) S° (J/mol?K) 121.2                       130.7              192.8

A) +133.7 J/K

B) -59.1 J/K

C) +118.2 J/K

D) -202.3 J/K

E) +178.9 J/K

52. Calculate DS°rxn for the following reaction. The S° for each species is shown below the reaction.

P4(g) + 10 Cl2(g) → 4 PCl5(g)

53. Give the name of the reaction that achieves the theoretical limits with respect to free energy in thermodynamics.
    1. Reversible reaction.
    2. Forward reaction.
    3. Reverse reaction.
    4. Equilibrium reaction.
    5. STP reaction.

54. Estimate DG°rxn for the following reaction at 449.0 K.

CH2O(g) + 2 H2(g) → CH4(g) + H2O(g)                     ΔH°= -94.9 kJ; ΔS°= -224.2 J/K

A) +5.8 kJ

B) +12.9 kJ

C) -101 kJ

D) +2.4 kJ

E) -4.2 kJ

55. Estimate ΔG°rxn for the following reaction at 387 K.

HCN(g) + 2 H2(g) → CH3NH2(g)                                  ΔH°= -158.0 kJ; ΔS°= -219.9 J/K

A) +243 kJ

B) -72.9 kJ

C) +84.9 kJ

D) -92.5 kJ

E) -188 kJ

56. Estimate ΔG°rxn for the following reaction at 775 K.

2 Hg(g) + O2(g) →  2 HgO(s)                                         ΔH°= -304.2 kJ; ΔS°= -414.2 J/K

1. 1. -625 kJ
   2. -181 kJ

C) +17 kJ

D) +321 kJ

E) -110 kJ

57. Determine ΔG°rxn using the following information.

FeO(s) + CO(g) → Fe(s) + CO2(g) ΔH°= - 11.0 kJ; ΔS°= - 17.4 J/K A) +191.0 kJ

B) -5.8 kJ

C) +1.6 kJ

D) -6.4 kJ

E) +89.5 kJ

58. Determine ΔG°rxn using the following information.

H2(g) + CO(g) →  CH2O(g)                                            ΔH°= + 1.9 kJ; ΔS°= - 109.6 J/K A) +57.7 kJ

B) -30.8 kJ

C) +34.6 kJ

D) -41.5 kJ

E) +17.3 kJ

59. Determine ΔG°rxn using the following information.

CaCO3(s) → CaO(s) + CO2(g)                    DH°= + 179.2 kJ; DS°= + 160.2 J/K A) -607.0 kJ

B) +112 .0 kJ

C) -89.3 kJ

D) +131.4 kJ

E) +228.1 kJ

60. Calculate the ΔG°rxn using the following information.

2 H2S(g) + 3 O2(g) → 2 SO2(g)  + 2 H2O(g)                             ΔG°rxn = ?

ΔG°f (kJ/mol) - 33.4                                            -3300.1             - 228.6

A) +112.4 kJ

B) -495.3 kJ

C) -528.7 kJ

D) +66.8 kJ

E) -990.6 kJ

61. Calculate the ΔG°rxn using the following information.

4 HNO3(g) + 5 N2H4(l) → 7 N2(g) + 12 H2O(l)                                      ΔG°rxn = ?

ΔG°f (kJ/mol)        -73.5                149.3                                                 -237.1

A) -3.298 x 103 kJ

B) -312.9 kJ

C) +2.845 x 103 kJ

D) +110.7 kJ

E) -954.7 kJ

62. Calculate the ΔG°rxn using the following information.

2 HNO3(aq) + NO(g) → 3 NO2(g) + H2O(l)                                            ΔG°rxn = ?

ΔG°f (kJ/mol) -110.9                 87.6                    51.3                -237.1

A) -162.5 kJ

B) +51.0 kJ

C) -54.5 kJ

D) +171.1 kJ

E) -87.6 kJ

63. Use Hess's law to calculate ΔG°rxn using the following information. CO(g) → C(s) + 1/2 O2(g)                                                                 ΔG°rxn = ?

CO2(g) → C(s) + O2(g)                                                    ΔG°rxn = +394.4 kJ

CO(g) + 1/2 O2(g) → CO2(g)                                        ΔG°rxn = -257.2 kJ

A) -60.0 kJ

B) +651.6 kJ

C) -265.8 kJ

D) +137.2 kJ

E) +523.0 kJ

64. Use Hess's law to calculate ΔG°rxn using the following information. ClO(g) + O3(g) → Cl(g) + 2 O2(g)                                                ΔG°rxn = ?

2 O3(g)→  3 O2(g)                                                           ΔG°rxn = +489.6 kJ

Cl(g) + O3(g) → ClO(g) + O2(g)                                  ΔG°rxn = -34.5 kJ

A) -472.4 kJ

B) -210.3 kJ

C) +455.1 kJ

D) +262.1 kJ

E) +524.1 kJ

65. Calculate the ΔG°rxn using the following information.

2 HNO3(aq) + NO(g) → 3 NO2(g)  + H2O(l) ΔG°rxn = ?

ΔH°f (kJ/mol) -207.0             91.3                    33.2                -285.8

S°(J/mol?K)              146.0         210.8                 240.1                 70.0

A) -151 kJ

B) -85.5 kJ

C) +50.8 kJ

D) +222 kJ

E) -186 kJ

66. Calculate the ΔG°rxn using the following information.

4 HNO3(g) + 5 N2H4(l) → 7 N2(g) + 12 H2O(l)                      ΔG°rxn = ?

ΔH°f (kJ/mol) -133.9                       50.6                                       -285.8

S°(J/mol?K)              266.9             121.2                 191.6                 70.0

A) +4.90 × 103 kJ

B) +3.90 × 103 kJ

C) -2.04 × 103 kJ

D) -3.15 × 103 kJ

E) -3.298 x 103 kJ

67. Calculate the ΔG°rxn using the following information.

2 H2S(g) + 3 O2(g) → 2 SO2(g)  +                  2 H2O(g)                    ΔG°rxn = ?

68. Use Hess's law to calculate ΔG°rxn using the following information. NO(g) + O(g) →  NO2(g)                                                                 ΔG°rxn = ?

2 O3(g) → 3 O2(g)                                                            ΔG°rxn = +489.6 kJ

O2(g) → 2 O(g)                                                                  ΔG°rxn = +463.4 kJ NO(g) + O3(g) → NO2(g) + O2(g)                                            ΔG°rxn = - 199.5 kJ

A) +753.5 kJ

B) +277.0 kJ

C) -676.0 kJ

D) -1152.5 kJ

E) -225.7 kJ

69. Calculate ΔGrxn at 298 K under the conditions shown below for the following reaction. SO3(g) + H2O(g) → H2SO4(l)                                                          ΔG°= -90.5 kJ

P(SO3) = 0.20 atm, P(H2O) = 0.88 atm

A) +15.9 kJ

B) -90.5 kJ

C) +51.4 kJ

D) -86.2 kJ

E) -30.4 kJ

70. Calculate ΔGrxn at 298 K under the conditions shown below for the following reaction. Fe2O3(s) + 3 CO(g) → 2 Fe(s) + 3 CO2(g) ΔG° = -28.0 kJ

P(CO) = 1.4 atm, P(CO2) = 2.1 atm

A) +31.0 kJ

B) +2.99 kJ

C) -30.7 kJ

D) +17.5 kJ

E) -25.0 kJ

71. Calculate ΔGrxn at 298 K under the conditions shown below for the following reaction. 3 O2(g)  → 2 O3(g)                                                                                 ΔG° = +326 kJ

P(O2) = 0.41 atm, P(O3) = 5.2 atm

A) +341 kJ

B) +17.8 kJ

C) +332 kJ

D) -47.4 kJ

E) -109 kJ

72. Calculate ΔGrxn at 298 K under the conditions shown below for the following reaction. 2 Hg(g) + O2(g) →  2 HgO(s)                                                            ΔG° = -180.8 kJ

P(Hg) = 0.025 atm, P(O2) = 0.037 atm

A) +207 kJ

B) -154.4 kJ

C) -26.5 kJ

D) -164 kJ

E) +60.7 kJ

73. Calculate ΔGrxn at 298 K under the conditions shown below for the following reaction. CaCO3(s) → CaO(s) + CO2(g)                                                          ΔG° =+131.1 kJ

P(CO2) = 0.033 atm

A) -49.3 kJ

B) -8.32 kJ

C) +122.6 kJ

D) +39.7 kJ

E) +43.3 kJ

74. Which of the following is not true for ΔGrxn?
    1. If ΔG°rxn > 0, the reaction is spontaneous in the forward direction.
    2. If Q = 1, then  DGrxn = ΔG°rxn.
    3. If ΔG°rxn = 0, the reaction is spontaneous in the reverse direction.
    4. If ΔG°rxn > 0, the reaction is spontaneous in the reverse direction.
    5. Under equilibrium conditions, ΔGrxn = 0.
75. Choose the statement below that is TRUE.
    1. K > 1, ΔG°rxn is positive
    2. K < 1, ΔG°rxn is negative
    3. ΔG°rxn = 0 at equilibrium
    4. ΔGrxn = 0 at equilibrium
    5. None of the above statements are true.

76. Which of the following reactions will have the largest equilibrium constant (K) at 298 K?
    1. CaCO3(s) → CaO(s) + CO2(g)    ΔG° =+131.1 kJ

B) 2 Hg(g) + O2(g) → 2 HgO(s)                           ΔG° = -180.8 kJ

C) 3 O2(g)  → 2 O3(g)                                              ΔG° = +326 kJ

D) Fe2O3(s) + 3 CO(g) → 2 Fe(s) + 3 CO2(g)                         ΔG° = -28.0 kJ

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

77. Use the free energies of formation given below to calculate the equilibrium constant (K) for the following reaction at 298 K.

2 HNO3(aq) + NO(g) → 3 NO2(g) + H2O(l)                                     K = ?

ΔG°f (kJ/mol) -110.9                 87.6                  51.3           -237.1

A) 8.71 × 108

B) 0.980

C) 1.15 × 10-9

D) 1.02

E) 5.11 × 10-4

78. Determine the equilibrium constant for the following reaction at 298 K. SO3(g) + H2O(g) → H2SO4(l)                                        ΔG° = -90.5 kJ

A) 1.37 × 10-16