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Ch 10 Practice Problems

1. Consider the process A(l) A(s). Which direction favors positional randomness?A) to the rightB) to the leftC) neitherD) It depends on the temperature.

2. Consider the process A(l) A(s). An increase in temperature favors which direction?A) to the rightB) to the leftC) neitherD) More information is needed.

3. A mixture of hydrogen and chlorine remains unreacted until it is exposed to ultraviolet light from a burning magnesium strip. Then the following reaction occurs very rapidly.H2(g) + Cl2(g) 2HCl(g) G = –45.54 kJ

H = –44.12 kJS = –4.76 J/K

Select the statement below that best explains this behavior.

A) The reactants are thermodynamically more stable than the products.B) The reaction has a small equilibrium constant.C) The ultraviolet light raises the temperature of the system and makes the reaction more favorable.D) The negative value for S slows down the reaction.E) The reaction is spontaneous, but the reactants are kinetically stable.

4. Consider the dissociation reaction of the acid HF

HF(aq) H+(aq) + F-(aq)

Why is S negative?

A) Each HF molecule produces two ions when it dissociates.B) The ions are hydrated.C) The reaction is expected to be exothermic, and S thus should be negative.D) The reaction is expected to be endothermic, and thus S should be negative.E) none of these

5. Which of the following result(s) in an increase in the entropy of the system?

I. (See diagram.)

II. Br2(g) Br2(l)

III. NaBr(s) Na+(aq) + Br–(aq)

IV. O2(298 K) O2(373 K)

V. NH3(1 atm, 298 K) NH3(3 atm, 298 K)

A) IB) II, VC) I, III, IVD) I, II, III, IVE) I, II, III, V

6. Calculate S when One mole of an ideal gas is compressed isothermally at 607.4 K from 5.60 atm to 8.90 atm. If the process is carried out in two irreversible steps (intermediate step at P = 7.00 atm).

A) 2.34 J/KB) -2.34 J/KC) -3.85 J/KD) 3.85 J/KE) 0 J/K

Use the following to answer questions 7-8:

One mole of an ideal gas expands isothermally and reversibly at 0°C. The pressure on 1 mol of an ideal monatomic gas changes from 100.0 atm to 1.00 atm.

7. Calculate w.A) 225 kJB) -225 kJC) 10.5 kJD) -10.5 kJE) 0

8. Calculate q.A) 225 kJB) -225 kJC) 10.5 kJD) -10.5 kJE) 0


A gas expands isothermally and irreversibly.

9. w is A) less than zero. B) equal to zero. C) greater than zero. D) More information is needed.10. q is A) less than zero.

B) equal to zero.C) greater than zero.D) More information is needed.

11. H isA) less than zero.B) equal to zero.C) greater than zero.D) More information is needed.

12. E isA) less than zero.B) equal to zero.C) greater than zero.D) More information is needed.

13. S isA) less than zero.B) equal to zero.C) greater than zero.D) More information is needed.

14. Ssurr isA) less than zero.B) equal to zero.C) greater than zero.D) More information is needed.

15. G isA) less than zero.B) equal to zero.C) greater than zero.D) More information is needed.


One mole of an ideal gas is compressed isothermally and reversibly at 607.4 K from 5.60 atm to 8.90 atm.

16. Calculate q.A) 298 kJB) -2.34 kJC) 2.34 kJD) -298 kJE) none of these

17. Calculate w.A) 298 kJB) -2.34 kJC) 2.34 kJD) -298 kJE) none of these

18. Calculate H.A) 0 kJB) -2.34 kJC) 2.34 kJD) 3.85 kJE) none of these


In an isothermal process, the pressure on 1 mol of an ideal monatomic gas suddenly changes from 4.00 atm to 100.0 atm at 25°C.

19. Calculate T.A) 25°CB) 48°CC) 100°CD) 0°CE) none of these

20. Calculate V.A) 5.87 LB) -5.87 LC) 6.11 LD) -6.11 LE) none of these

21. Calculate w.A) -59.5 kJB) 59.5 kJC) 23.5 kJD) -23.5 kJE) 0

22. One mole of an ideal gas at 25°C is expanded isothermally from 5.0 L to 10.0 L under such conditions that no work is produced in the surroundings. Which statement is correct?A) Sgas = 0B) Sgas = Rln2/298C) Suniv = 0D) Ssurr = 0E) Sgas = Ssurr

23. A rigid insulated box contains 20.0 g of He(g) at 25.0° C and 1.00 atm in one compartment and 20.0 g of N2(g) at 115° C and 2.00 atm in the other compartment. These compartments are connected by a partition that transmits heat. What is the final temperature in the box at thermal equilibrium? (Cv(He) = 12.5 J/K•mol; Cv(N2) = 20.7 J/K•mol)A) 42.3°CB) 58.9°CC) 70.0°CD) 81.0°CE) none of these

24. One mole of an ideal gas at 25°C is expanded isothermally and reversibly from 125.0 L to 250.0 L. Which statement is correct?A) Sgas = 0B) Sgas = Rln2C) Suniv = 0D) Ssurr = 0E) Sgas = Ssurr

25. Which statement is true?A) All real processes are irreversible.B) A thermodynamically reversible process takes place infinitely fast.C) In a reversible process, the state functions of the system are always much greater than those of the surroundings.D) There is always more heat given off to the surroundings in a reversible process than in an unharnessed one.E) All these statements are true.

26. A machine employs the isothermal expansion of 1 mol of an ideal gas from 4.50 L to 15.0 L. At 25°C, the machine performs 3.00 kJ of work. What percent of the maximum possible work is the machine producing?A) 4.50%B) 50.3%C) 0.60%D) 15.0%E) This amount of work cannot be correct.

Use the following to answer question 27:


27. Calculate E.A) 59.5 kJB) 119 kJC) -59.5 kJD) 0 kJE) none of these

28. If the change in entropy of the surroundings for a process at 451 K and constant pressure is –348 J/K, what is the heat flow absorbed by the system?A) 772 kJB) 18.9 kJC) –157 kJD) -18.9 kJE) 157 kJ


One mole of an ideal gas expands isothermally and reversibly at 0°C. The pressure on 1 mol of an ideal monatomic gas changes from 100.0 atm to 1.00 atm.

29. Calculate E.A) 450 kJB) -450 kJC) 21.0 kJD) -21.0 kJE) none of these


One mole of an ideal gas is compressed isothermally and reversibly at 607.4 K from 5.60 atm to 8.90 atm.

30. Calculate S.A) 2.34 J/KB) -2.34 J/KC) -3.85 J/KD) 3.85 J/KE) 0

31. S is _______ for exothermic reactions and ______ for endothermic reactions.A) favorable, unfavorableB) unfavorable, favorableC) favorable, favorableD) unfavorable, unfavorableE) cannot tell

32. 1.2 mol of an ideal gas at 304 K is compressed isothermally and reversibly from 1.8 L to 0.50 L. What is S?A) 13 J/KB) –3.9 kJ/KC) –11 J/KD) –13 J/KE) –6 J/K

33. In a certain reversible expansion, a system at 300. K absorbs exactly 6.00 102 J of heat. In the irreversible recompression to the original state of the system, twice as much work is done on the system as is performed on the surroundings in the expansion. What is the entropy change of the system in the recompression step?A) -4.00 J/KB) -2.00 J/KC) 0.00 J/KD) 2.00 J/KE) 4.00 J/K

34. Calculate G for the isothermal compression of 1 mol of an ideal monatomic gas from 1.4 atm to 5.6 atm at 23°C.A) 3.4 103 JB) 1.6 103 JC) -3.4 103 JD) -1.6 103 JE) 5.1 103 J

35. Calculate the entropy change when 5.00 mol of a monatomic ideal gas is cooled from 135°C to 85°C at 1 atm.A) -250.0 J/KB) -9.62 J/KC) -48.9 J/KD) -13.6 J/KE) -2.74 J/K

36. Which of the following is true?A) As long as the disorder of the surroundings is increasing, a process will be spontaneous.B) For any process, Ssurr and Ssys have opposite signs.C) If Ssurr = -Ssys , the process is at equilibrium.D) H° is zero for a chemical reaction at constant temperature.E) none of these

37. Ssurr is _______ for exothermic reactions and ______ for endothermic reactions.A) favorable, unfavorableB) unfavorable, favorableC) favorable, favorableD) unfavorable, unfavorableE) cannot tell


At 1 atm, a liquid is heated above its normal boiling point.

38. Ssurr for this process isA) greater than zero.B) less than zero.C) equal to zero.D) cannot be determined

39. S for this process isA) greater than zero.B) less than zero.C) equal to zero.D) cannot be determined

40. Suniv for this process isA) greater than zero.B) less than zero.C) equal to zero.D) cannot be determined

41. Choose the correct statement.A) Exothermic reactions are always spontaneous.B) Free energy is independent of temperature.C) A reaction that exhibits a negative value of S cannot be spontaneous.D) At constant pressure and temperature, a decrease in free energy ensures an increase in the entropy of the system.E) none of these

42. For which process is S negative?A) evaporation of 1 mol of CCl4(l)B) mixing 5 mL of ethanol with 25 mL of waterC) compressing 1 mol of Ne at constant temperature from 1.5 atm to 0.5 atmD) raising the temperature of 100 g of Cu from 275 K to 295 KE) grinding a large crystal of KCl to powder

43. When a gas is expanded isothermally and reversibly at 38°C, the work done is -42.6 kJ. Calculate S.A) 1121 J/KB) 1.12 kJ/KC) 1.37 102 J/KD) -1139 J/KE) -1.12 kJ/K

44. A 100-mL sample of water is placed in a coffee cup calorimeter. When 1.0 g of an ionic solid is added, the temperature decreases from 21.5°C to 20.8°C as the solid dissolves. Which of the following is true for the dissolving of the solid?A) H < 0B) Suniv > 0C) Ssys< 0D) Ssurr > 0E) none of these


The process H2O(g) H2O(l) takes place at 1 atm and 95°C.

45. What is w?A) less than zeroB) equal to zeroC) greater than zeroD) More information is needed.

46. What is q?A) less than zeroB) equal to zeroC) greater than zeroD) More information is needed.

47. What is H?A) less than zeroB) equal to zeroC) greater than zeroD) More information is needed.

48. What is S?A) less than zeroB) equal to zeroC) greater than zeroD) More information is needed.

49. What is G?A) less than zeroB) equal to zeroC) greater than zeroD) More information is needed.

50. Assume that the enthalpy of fusion of ice is 6020 J/mol and does not vary appreciably over the temperature range 270–290 K. If 2.20 mol of ice at 0°C is melted by heat supplied from surroundings at 284 K, what is the entropy change in the surroundings in J/K?A) +48.5B) +45.5C) 0.0D) –45.5E) –48.5

51. 5.50 mol of a monatomic ideal gas is cooled from 246°C to 27°C at constant volume. Calculate S.A) –62.7 J/KB) –16.3 J/KC) –27.2 J/KD) –37.6 J/KE) –1.52 102 J/K

52. Calculate the minimum work required to compress 1.9 mol of an ideal monatomic gas from 47.4 L to 15.6 L at 27°C.A) 4.7 102 JB) -7.9 103 JC) 7.9 103 JD) 5.3 103 JE) 2.8 102 J

53. Calculate S for cooling 2.60 mol of an ideal monatomic gas from 87°C to 41°C at constant volume.A) –24.4 J/KB) –4.43 J/KC) –2.96 J/KD) –16.3 J/KE) –1.70 J/K

54. Calculate S for cooling 1.5 mol of an ideal monatomic gas from 81°C to 36°C at constant pressure.A) –1.70 J/KB) –25.3 J/KC) –4.24 J/KD) –2.54 J/KE) –2.83 J/K

55. Calculate S for an isothermal (95°C) expansion of 2 mol of a monatomic ideal gas from 100.0 atm to 1.00 atm.A) 76.6 J/KB) -76.6 J/KC) -38.3 J/KD) 38.3 J/KE) none


Substance X has a heat of vaporization of 55.4 kJ/mol at its normal boiling point (423°C). For the process X( l) X(g) at 1 atm and 423°C, calculate the value of:

56. GA) 0B) 79.6 J/K•molC) 103 J/K•molD) -79.6 J/K•molE) -103 J/K•mol

57. Suniv

A) 0B) 79.6 J/K•molC) 103 J/K•molD) -79.6 J/K•molE) -103 J/K•mol



58. Calculate G.A) 7.98 kJB) -7.98 kJC) 59.5 kJD) 0 kJE) none of these

59. Calculate S.A) 20.5 J/KB) -20.5 J/KC) 26.8 J/KD) -26.8 J/KE) none of these


Substance X has a heat of vaporization of 55.4 kJ/mol at its normal boiling point (423°C). For the process X( l) X(g) at 1 atm and 423°C, calculate the value of:

60. Ssurr

A) 0B) 79.6 J/K•molC) 103 J/K•molD) -79.6 J/K•molE) -103 J/K•mol

61. SA) 0B) 79.6 J/K•molC) 103 J/K•molD) -79.6 J/K•molE) -103 J/K•mol

62. Consider the freezing of liquid water at –10°C. For this process what are the signs for H, S, and G, respectively?A) + – 0B) – + 0C) – + –D) + – –E) – – –

63. In which case must a reaction be spontaneous at all temperatures?A) H is positive, S is positiveB) H = 0, S is negativeC) S = 0, H is positiveD) H is negative, S is positiveE) none of these

64. The dissociation of hydrogen H2(g) 2H(g)

A) is spontaneous at any temperature.B) is spontaneous at high temperature.C) is spontaneous at low temperature.D) is independent of temperature.E) never takes place.



65. Calculate H.A) 59.5 kJB) -119 kJC) -59.5 kJD) 0 kJE) none of these

66. As O2(l) is cooled at 1 atm, it freezes at 54.5 K to form Solid I. At a lower temperature, Solid I rearranges to Solid II, which has a different crystal structure. Thermal measurements show that H for the I II phase transition is –743.1 J/mol and that S for the same transition is –17.0 J/K mol. At what temperature are Solids I and II in equilibrium?A) 2.06 KB) 43.7 KC) 31.5 KD) 53.4 KE) They can never be in equilibrium because they are both solids.

67. When a stable diatomic molecule spontaneously forms from its atoms, what are the signs of H°, S°, and G°, respectively?A) + + +B) + – –C) – + +D) – – +E) – – –


Consider the reaction 2N2O5(g) 4NO2(g) + O2(g)at 25°C, for which the following data are relevant:

H°f (kJ/mol) S° (J/K•mol)N2O5 11.29 355.3NO2 33.15 239.9O2 ? 204.8

68. Which of the following is true for this reaction?A) Both H° and S° favor the reaction's spontaneity.B) Both H° and S° oppose the reaction's spontaneity.C) H° favors the reaction, but S° opposes it.D) H° opposes the reaction, but S° favors it.E) The reaction cannot occur at room temperature.

69. Elemental sulfur exists in two crystalline forms, rhombic and monoclinic. From the following data, calculate the temperature at which monoclinic sulfur and rhombic sulfur are in equilibrium.

Hf° (kJ/mol) S° (J/K•mol)S (rhombic) 0 31.88S (monoclinic) 0.30 32.55

A) +450 KB) +210 KC) –210 KD) –450 KE) 0 K

70. For a spontaneous endothermic process, which conditions must hold?1) wmax = G

2) Ssurr > 0

3) S cannot be negative.

4) S is positive.

A)allB) noneC) 1 and 3 onlyD)1, 2, and 4 onlyE) 3 and 4 only

71. For the vaporization of a liquid at a given pressure,A) G is positive at all temperatures.B) G is negative at all temperatures.C) G is positive at low temperatures but negative at high temperatures (and zero at some temperature).D) G is negative at low temperatures but positive at high temperatures (and zero at some temperature).

72. For the reaction A + B C + D, H° = +40 kJ and S° = +50 J/K. Therefore, the reaction under standard conditions isA) spontaneous at temperatures less than 10 K.B) spontaneous at temperatures greater than 800 K.C) spontaneous only at temperatures between 10 K and 800 K.D) spontaneous at all temperatures.E) nonspontaneous at all temperatures.

73. For the process involving compound A: A(s) A(l), H° = 7.5 kJ/mol, and S° = 43.4 J/mol•K. What is the melting point of compound A?A) –100°CB) 173°CC) –222°CD) 100°CE) –173°C

74. Given the following data, calculate the normal boiling point for formic acid (HCOOH).H°f (kJ/mol) S° (J/K•mol)

HCOOH(l) -410. 130.HCOOH(g) -363 251

A) 2.57 KB) 1730°CC) 388°CD) 82°CE) 115°C

75. At constant pressure, the reaction 2NO2(g) N2O4(g)

is exothermic. The reaction (as written) is

A) always spontaneous.B) spontaneous at low temperatures but not at high temperatures.C) spontaneous at high temperatures but not at low temperatures.D) never spontaneous.

76. For the process moleene(l) moleene(g) at 1 atm, Hvap = 37.6 kJ/mol and Svap = 67.8 J/mol•K. Assuming these values are independent of T, what is the normal boiling point of moleene?A) 828°CB) 282°CC) 378°CD) –282°CE) 555°C


The vapor pressure of Br2(l) at 25°C is 0.281 atm, and 193 J is required to vaporize 1.00 g of bromine at 1 atm pressure.

77. Calculate H° for the vaporization of Br2(l) at 25°C and 1 atm.A) 0.193 kJ/molB) 30.8 kJ/molC) 15.4 kJ/molD) 1.21 kJ/molE) none of these

78. Calculate S° for the vaporization of Br2(l) at 25°C and 1 atm.A) 92.8 J/K•molB) 103 J/K•molC) 0 J/K•molD) 30.8 J/K•molE) none of these

79. Assuming H° and S° are temperature independent, calculate the normal boiling point of bromine.A) 25°CB) 332°CC) 332 KD) 0°CE) none of these

80. Calculate G for the vaporization of Br2(l) at 25°C and 1 atm.A) 0.378 kJ/molB) 0.263 kJ/molC) 3.15 kJ/molD) 0E) none of these

81. In which reaction is S° 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




82. Calculate S° for the reaction.A) 89.5 J/KB) -249.2 J/KC) 453.8 J/KD) 249.2 J/KE) –115.6 J/K

83. For which of the following processes would S° be expected to be most positive?A) O2(g) + 2H2(g) 2H2O(g)B) H2O(l) H2O(s)C) NH3(g) + HCl(g) NH4Cl(g)D) 2NH4NO3(s) 2N2(g) + O2(g) + 4H2O(g)E) N2O4(g) 2NO2(g)

84. Consider the following hypothetical reaction at 340 K. Standard free energies of formation are given in parentheses.B C G° = –38.4 kJ/mol(?) (165.5 kJ/mol)

Calculate the standard free energy of formation of compound B.

A) 203.9 kJ/molB) 127.1 kJ/molC) -203.9 kJ/molD) –127.1 kJ/molE) –292.6 kJ/mol

85. The standard free energy of formation of AgBr(s) is –97.0 kJ/mol. Calculate G° for the reaction

2AgBr(s) 2Ag(s) + Br2(g)

A) 97.0 kJB) 194 kJC) –97.0 kJD) –194 kJE) 44.0 kJ

86. The reaction 2H2O(g) 2H2(g) + O2(g)

has a positive value of G°. Which of the following statements must be true?

A) The reaction is slow.B) The reaction will not occur. That is, when H2O(g) is introduced into a flask, no O2 or H2 will form even over a long period

of time.C) The reaction is exothermic.D) The equilibrium lies far to the right.E) None of these is true.

87. The standard free energy of formation of N2(g) at 25°C is zero. Calculate Gf (25°C), in kilojoules per mol, for N2 at 1000 atm. Assume ideal gas behavior.A) +39.4 kJ/molB) +17.1 kJ/molC) 0 kJ/molD) –17.1 kJ/molE) -39.4 kJ/mol

88. At 699 K, G° = –23.25 kJ for the reaction H2(g) + I2(g) 2HI(g). Calculate G for this reaction if the reagents are both supplied at 10.0 atm pressure and the product is at 1.00 atm pressure.A) –3.5 kJB) –36.6 kJC) +36.6 kJD) –50.0 kJE) +50.0 kJ


Given CH3CO2H(aq) H+(aq) + CH3CO2

–(aq)at 25°C, Ka = 1.8 10–5

89. What is G at 25°C for a solution in which the initial concentrations are[CH3CO2H]o = 0.10 M

[H+]o = 2.0 10–8 M[CH3CO2

–]o = 0.010 M

A) +50. kJB) –50. kJC) +23 kJD) –23 kJE) 27 kJ

90. What is G° at 25°C?A) –27,000 JB) +27,000 JC) –2300 JD) +2300 JE) +270 J




91. Calculate H° for the reaction.A) 110.02 kJB) 21.86 kJC) –21.86 kJD) 115.20 kJE) –155.20 kJ

92. Calculate G° for the reaction at 25°C.A) –135 kJB) 98.7 kJC) –25.2 kJD) –11.2 kJE) 0

93. The reaction is allowed to proceed until all substances involved have reached their equilibrium concentrations. Under those conditions, what is G for the reaction?A) –135 kJB) 98.7 kJC) –25.2 kJD) –11.2 kJE) 0

94. For the reaction CO2(g) + 2H2O(g) CH4(g) + 2O2(g), H° = 803 kJ

which of the following will increase K?

A) decreasing the number of moles of methaneB) increasing the volume of systemC) increasing the temperature of systemD) all of theseE) none of these

95. Assume that the reaction CO(g) + H2O(g) CO2(g) + H2(g)

occurs in an mixture of ideal gases. At 700 K, Kp = 5.10. At this temperature, what is G°?

A) 0 kJB) 29.7 kJC) 9.48 kJD) –9.48 kJE) –4.12 kJ

96. The equilibrium constant Kp for the dissociation reaction of Cl2

Cl2(g) 2Cl(g)

was measured as a function of temperature (in K). A graph of ln Kp versus 1/T for this reaction gives a straight line with a slope of –1.352 104 and an intercept of 14.51. What is the value of S for this dissociation reaction?

A)26.81 J/K•molB) 112.0 J/K•molC) 120.6 J/K•molD)53.14 J/K•molE) none of these

97. The following reaction has a G° value of 42.6 kJ/mol at 25°C.

HB(aq) + H2O(l) H3O+(aq) + B–(aq)

Calculate Ka for the acid HB.

A) 1.63B) –17.2C) 3.41 10–8

D) 42,600E) 14.0


Consider the gas phase reaction NO + (1/2)O2 NO2

for which H° = –57.0 kJ and K = 1.5 106 at 25°C.

98. Calculate H° at 25°C for the following reaction: 2NO + O2 2NO2

A) 57.0 kJB) –114 kJC) –28.5 kJD) 778 kJ

99. Calculate K for the following reaction at 25°C: 2NO + O2 2NO2

A) 3.0 106

B) 2.3 1012

C) 7.5 105

D) 1.2 103

E) 1.5 106

100. Calculate G° at 25°C for the following reaction: 2NO + O2 2NO2

A) –70.5 kJB) –5.91 kJC) –57.0 kJD) +5.91 kJE) +70.5 kJ

101. Calculate S° at 25°C for the following reaction: 2NO + O2 2NO2

A) –1740 J/KB) –146 J/KC) +528 J/KD) +146 J/KE) +1740 J/K

102. For this system at equilibrium, how will raising the temperature affect the amount of NO present?A) The amount of NO will increase.B) The amount of NO will decrease.C) The amount of NO will remain the same.

103. What will be the effect on the amount of NO present of compressing the equilibrium system to a smaller volume, while keeping the temperature constant?A) The amount of NO will increase.B) The amount of NO will decrease.C) The amount of NO will remain the same.

104. The standard free energy of formation of nitric oxide, NO, at 1000. K (roughly the temperature in an automobile engine during ignition) is 78 kJ/mol. Calculate the equilibrium constant for the reaction N2(g) + O2(g) 2NO(g)

at 1000. K.

A) 1.8 10–19

B) 0.99C) 4.3 10–10

D) 7.1 10–9

E) 8.4 10–5


Consider the following system at equilibrium at 25°C: PCl3(g) + Cl2(g) PCl5(g) for which H° = –92.5 kJ at 25°C.

105. When the temperature of the system is raised, the ratio of the partial pressure of PCl5 to the partial pressure of PCl3 willA) increase.B) decrease.C) stay the same.D) It is impossible to tell without more information.

106. When some Cl2(g) is added at constant volume and temperature, the ratio of the partial pressure of PCl5 to the partial pressure of PCl3 willA) increase.B) decrease.C) stay the same.D) It is impossible to tell without more information.

107. When the volume is decreased at constant temperature, the ratio of the partial pressure of PCl5 to the partial pressure of PCl3 willA) increase.B) decrease.C) stay the same.D) It is impossible to tell without more information.

108. Consider a weak acid, HX. The value of G° for the acid's dissociation reaction at 25°C is 42.6 kJ. Determine the value of Ka for the acid.A) 1.63B) 3.41 10–8

C) 4.26 105

D) 2.86 10–6

E) none of these


The equilibrium constant Kp (in atm) for the dissociation reaction of Cl2

Cl2 2Cl was measured as a function of temperature (in K). A graph of ln Kp versus 1/T for this reaction gives a straight line with a slope of –1.352 104 and an intercept of 14.51.

109. From these data, which of the following statements is true?A) The reaction is exothermic.B) The reaction is endothermic.C) The reaction is spontaneous.D) None of these statements is true.

110. What is the value of H for this dissociation reaction?A) –122.1 kJB) 112.4 kJC) 26.8 kJD) 122.1 kJE) none of these

111. Given the following free energies of formation:

GC2H2(g) 209.2 kJ/molC2H6(g) –32.9 kJ/mol

calculate Kp at 298 K for C2H2(g) + 2H2(g) C2H6(g).

A) 9.07 10–1

B) 97.2C) 1.24 1031

D) 2.72 1042

E) None of these is within a factor of 10 of the correct answer.

112. The acid dissociation constant for a weak acid HX at 25°C is 2.04 10–8. Calculate the free energy of formation for X–(aq) at 25°C. The standard free energies of HX(aq) and H+(aq) at 25°C are –328.2 kJ/mol and 0, respectively.A) 284 kJ/molB) 372 kJ/molC) -309 kJ/molD) –284 kJ/molE) -372 kJ/mol

113. The standard molar free energies of formation of NO2(g) and N2O4(g) at 25°C are 51.84 and 98.28 kJ/mol, respectively. What is the value of Kp (in atm) for the reaction written as follows at 25°C? 2NO2 N2O4

A) 1.37 108

B) 1.17 104

C) 8.84D) 0.113E) 7.31 10–9

114. For the reaction Cl2O(g) + (3/2)O2(g) 2ClO2(g), H° = 126.4 kJ/mol and S° = –74.9 J/Kmol. What is G° at 377°C?A) 98.3 kJ/molB) 77.8 kJ/molC) 175.1 kJ/molD) 51.5 kJ/molE) none of these

115. Given that G°f for NH3 = –16.67 kJ/mol, calculate the equilibrium constant for the following reaction at 298 K. N2(g) + 3H2(g) 2NH3(g)

A) 6.98 105

B) 8.36 102

C) 8.36 10–2

D) 1.20 10–3

E) 1.42 10–6

116. Consider the reaction 2SO2(g) + O2(g) 2SO3(g)

for which H° = –200. kJ and S° = –187 J/K at 25°C. Assuming that H° and S° are independent of temperature, calculate the temperature where Kp = 1.

A) 970. KB) 2070 KC) 200. KD) 1070 KE) none of these

117. For a particular reaction, the equilibrium constant is 1.60 10–2 at 326°C, and H° is +12.2 kJ at 25°C. Assuming H° and S° are temperature independent, calculate S° for the reaction.A) 14.0 J/KB) 54.7 J/KC) –14.0 J/KD) –54.7 J/KE) 5.44 J/K

118. Calculate G° for H2O(g) + 1/2O2(g) H2O2(g) at 600. K, using the following data:

H2(g) + O2(g) H2O2 Kp = 2.3 106 at 600. K

2H2(g) + O2(g) 2H2O(g) Kp = 1.8 1037 at 600. K

A) +140 kJB) –220 kJC) –290 kJD) –350 kJE) +290 kJ

119. Consider the following hypothetical reaction (at 319 K). Standard free energies, in kJ/mol, are given in parentheses.A B + C G° = ?

(–32.6) (207.8) (–237.0)What is the value of the equilibrium constant for the reaction at 319 K?

A) 0.28B) 0.10C) 1.0D) 3.4 1010

E) 1.3

120. Consider the reaction 2NO2(g) N2O4(g); H° = –56.8 kJ S° = –175 J/K

In a container (at 298 K), N2O4(g) and NO2(g) are mixed with initial partial pressures of 2.4 atm and 0.42 atm, respectively. Which of the following statements is correct?

A) Some N2O4(g) will decompose into NO2(g).B) Some NO2(g) will dimerize to form N2O4(g).C) The system is at equilibrium at these initial pressures.D) The final total pressure must be known to answer this question.E) None of these statements is correct.

121. Given that S° = 131 J/Kmol for H2(g), estimate the value of S° for the reactionTi(s) + H2(g) TiH2(s)

A) 0B) 262 J/KC) 131 J/KD) –131 J/KE) –262 J/K

122. For the reaction CO(g) + 2H2(g) CH3OH(g), G°700K = –13.46 kJ. What is Kp for this reaction at 700. K?A) 10.1B) 16.7C) 22.5D) 9.90 10–2

E) none of these

123. For the reaction 2HF(g) H2(g) + F2(g), G° = 38.3 kJ at 1000 K. If, at this temperature, 5.00 mol of HF(g), 0.500 mol of H2(g), and 0.75 mol of F2(g) are mixed in a 1.00-L container:A) Some HF will decompose (to yield H2 and F2).B) The system is at equilibrium.C) Some HF will be formed (from H2 and F2).D) Not enough data are given to answer this question.

124. Water gas, a commercial fuel, is made by the reaction of hot coke carbon with steam.C(s) + H2O(g) CO(g) + H2(g)

When equilibrium is established at 800°C, the concentrations of CO, H2, and H2O are 4.00 10-2 mol/L, 4.00 10-2 mol/L, and 1.00 10-2 mol/L, respectively. Calculate the value of G° for this reaction at 800°C.

A) 109 kJB) –43.5 kJC) 193 kJD) 16.3 kJE) none of these

125. For a certain process, at 313 K, G = –22.5 kJ and H = –7.00 kJ. If the process is carried out reversibly, what is the amount of useful work that can be performed?A) –49.5 kJB) –7.00 kJC) –15.5 kJD) –22.5 kJE) –29.5 kJ

126. For a certain process, at 322 K, G = –16.0 kJ and H = –5.00 kJ. If the process is carried out in such a way that no useful work is performed, what is G?A) 16.0 kJB) 11.0 kJC) 0D) –11.0 kJE) –16.0 kJ

127. In which of the following changes is the work done by the system the largest at 25°C?A) an isothermal free expansion of an ideal gas from 1 L to 10 LB) an isothermal expansion of an ideal gas from 1 L to 10 L against an opposing pressure of 1 atmC) an isothermal expansion of an ideal gas from 1 L to 10 L against an opposing pressure of 5 atmD) an isothermal reversible expansion of an ideal gas from 1 L to 10 LE) The work is the same for all these processes.


One mole of an ideal gas is compressed isothermally at 607.4 K from 5.60 atm to 8.90 atm. If the process is carried out in two irreversible steps (intermediate step at P = 7.00 atm), calculate the following.

128. wtotal

A) -2.63 kJB) 2.63 kJC) -2.34 kJD) 2.34 kJE) none of these

129. A 1.00-mol sample of an ideal monatomic gas is compressed isothermally and irreversibly in one step from 2.50 atm to 6.50 atm at 300.0 K. Calculate w, H, G, and Ssurr for this process.

130. For the process A(l) A(g), H° = 4.50 kJ/mol at 100.0°C and 1 atm. At constant pressure, the molar heat capacities (Cp) are as follows: A(l), 65.0 J/K•mol; A(g), 28.0 J/K•mol. Calculate H° for this process at 75.0°C.

131. Calculate w and E when 1 mol of a liquid is vaporized at its normal boiling point (80.0°C). H for the vaporization of the liquid is 30.7 kJ/mol.

132. Consider the reaction below at 25°C, for which the following data are relevant.2N2O5(g) 4NO2(g) + O2(g)

H°f (kJ/mol) S° (J/K•mol)N2O5(g) -42 178NO2(g) 34 240O2(g) 0 205

Calculate H°, S°, and G° for this reaction at 25°C.

Answers1. B 11. B 21. B 31. E 41. E 51. D 61. B 71. C 81. E 91. A2. B 12. B 22. D 32. D 42. C 52. D 62. E 72. B 82. C 92. C3. E 13. C 23. A 33. B 43. C 53. B 63. D 73. A 83. D 93. E

4. B 14. A 24. C 34. A 44. B 54. C 64. B 74. E 84. A 94. C5. C 15. A 25. A 35. D 45. C 55. A 65. D 75. B 85. B 95. D6. C 16. B 26. E 36. C 46. A 56. A 66. B 76. B 86. E 96. C7. D 17. C 27. D 37. A 47. A 57. A 67. E 77. B 87. B 97. C8. C 18. A 28. E 38. B 48. A 58. A 68. D 78. A 88. D 98. B9. A 19. D 29. E 39. A 49. A 59. D 69. A 79. C 89. D 99. B

10. C 20. B 30. C 40. A 50. D 60. D 70. C 80. C 90. B 100. A

101. B 111. D 121. D102. A 112. D 122. A103. B 113. C 123. C104. D 114. C 124. D105. B 115. A 125. D106. A 116. D 126. E107. A 117. C 127. D108. B 118. A 128. B109. B 119. A110. B 120. A

129. w = 3.99 kJ, ΔH = 0, ΔG = 2.38 kJ, ΔSsurr = 13.3 J/K 130. ΔH° = 5.43 kJ131. w = -2.94 kJ, ΔE = 27.8 kJ132. ΔH° = 220.0 kJ, ΔS° = 809.0 J/K, ΔG° = -21.1 kJ

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