Practice for Exam2: Chemistry 220 Fall 2008 Created: 8:39:48 AM MST

Student: _________________________________________________________

1. The substance NH3 is considered A. a weak acid. B. a weak base. C. a strong acid. D. a strong base. E. a neutral compound.

2. The substance (CH3CH2)2NH is considered A. a weak acid. B. a weak base. C. a strong acid. D. a strong base. E. a neutral compound.

3. The substance HClO4 is considered A. a weak acid. B. a weak base. C. a strong acid. D. a strong base. E. a neutral compound.

4. Which of the following is the strongest acid? A. CH3COOH B. HF C. H3PO4 D. H2SO3 E. HI

5. Which of the following pairs has the stronger acid listed first? A. HBr, HI B. HClO2, HClO3 C. H2SeO4, H2SeO3 D. HNO2, HNO3 E. HF, HCl

6. Which of the following acids has the lowest pH? 0.1 M HBO, pKa = 2.43 0.1 M HA, pKa = 4.55 0.1 M HMO, pKa = 8.23 0.1 M HST, pKa = 11.89 pure water

A. HA B. HST C. HMO D. HBO E. pure water

7. Which of the following liquids contains the strongest acid?

0.1 M HA, pH = 6.85 0.1 M HD, pH = 7.22 0.1 M HE, pH = 8.34 0.1 M HJ, pH = 11.88 pure water

A. HE B. HA C. HJ D. HD E. pure water

8. What is the pH of a 0.20 M HCl solution? A. < 0 B. 0.70 C. 1.61 D. 12.39 E. 13.30

9. What is the pH of a 0.75 M HNO3 solution? A. 0.12 B. 0.29 C. 0.63 D. 0.82 E. > 1.0

10. What is the pH of a 0.050 M LiOH solution? A. < 1.0 B. 1.30 C. 3.00 D. 11.00 E. 12.70

11. What is the pH of a 0.0125 M NaOH solution? A. 0.972 B. 1.903 C. 12.097 D. 13.028 E. none of these choices is correct

12. What is the [OH-] for a solution at 25C that has [H3O+] = 2.35 10-3 M? A. 4.26 10-5 M B. 2.35 10-11 M C. 4.26 10-12 M D. 2.35 10-17 M E. none of these choices is correct

13. What is the [OH-] for a solution at 25C that has [H3O+] = 8.23 10-2 M? A. > 10-5 M B. 1.22 10-6 M C. 8.23 10-12 M D. 1.22 10-13 M E. 8.23 10-16 M

14. What is the [H3O+] for a solution at 25C that has pOH = 5.640? A. 2.34 10-4 M B. 2.29 10-6 M C. 4.37 10-9 M D. 4.27 10-11 M E. 8.360 M

15. Select the pair of substances in which an acid is listed followed by its conjugate base. A. H+, HCl B. NH3, NH4+ C. HPO42-, H2PO4- D. HCO3-, CO32- E. CH3COOH, CH3COOH2+

16. Select the pair of substances which is not a conjugate acid-base pair. A. H3O+, H2O B. HNO2, NO2- C. H2SO4, HSO4- D. H2S, S2- E. NH3, NH2-

17. Which one of the following pairs is not a conjugate acid-base pair? A. H2O/OH- B. H2O2/HO2- C. OH-/O2- D. H2PO4-/HPO42- E. HCl/H+

18. The acid dissociation constant Ka equals 1.26 10-2 for HSO4- and is 5.6 10-10 for NH4+. Which statement about the following equilibrium is correct? HSO4-(aq) + NH3(aq) SO42-(aq) + NH4+(aq)

A. The reactants will be favored because ammonia is a stronger base than the sulfate anion. B. The products will be favored because the hydrogen sulfate ion is a stronger acid than the

ammonium ion. C. Neither reactants or products will be favored because all of the species are weak acids or

bases. D. The initial concentrations of the hydrogen sulfate ion and ammonia must be known before

any prediction can be made. E. This reaction is impossible to predict, since the strong acid and the weak base appear on the

same side of the equation. 19. Butyric acid is responsible for the odor in rancid butter. A solution of 0.25 M butyric acid has a pH of 2.71.

What is the Ka for the acid? A. 0.36 B. 2.4 10-2 C. 7.8 10-3 D. 1.5 10-5 E. none of these choices is correct

20. A 0.15 M solution of chloroacetic acid has a pH of 1.86. What is the value of Ka for this acid? A. 7.2 101 B. 0.16

C. 0.099 D. 0.0014 E. 0.00027

21. Formic acid, which is a component of insect venom, has a Ka = 1.8 10-4. What is the [H3O+] in a solution that is initially 0.10 M formic acid, HCOOH?

A. 4.2 10-3 M B. 8.4 10-3 M C. 1.8 10-4 M D. 1.8 10-5 M E. 1.8 10-6 M

22. Picric acid has been used in the leather industry and in etching copper. However, its laboratory use has been restricted because it dehydrates on standing and can become shock sensitive. It has an acid dissociation constant of 0.42. What is the [H3O+] for a 0.20 M solution of picric acid?

A. 0.022 M B. 0.052 M C. 0.15 M D. 0.29 M E. none of these choices is correct

23. Lactic acid has a pKa of 3.08. What is the approximate degree of dissociation of a 0.35 M solution of lactic acid?

A. 1.1% B. 2.2% C. 4.8% D. 14% E. none of these choices is correct

24. Farmers who raise cotton once used arsenic acid, H3AsO4, as a defoliant at harvest time. Arsenic acid is a polyprotic acid with K1 = 2.5 10-4, K2 = 5.6 10-8, and K3 = 3 10-13. What is the pH of a 0.500 M solution of arsenic acid?

A. 0.85 B. 1.96 C. 3.90 D. 4.51 E. none of these choices is correct

25. What is the pH of a 0.050 M triethylamine, (C2H5)3N, solution? Kb for triethylamine is 5.3 10-4.

A. 11.69 B. 8.68 C. 5.32 D. 2.31 E. < 2.0

26. Hydroxylamine, HONH2, readily forms salts such as hydroxylamine hydrochloride which are used as antioxidants in soaps. Hydroxylamine has Kb of 9.1 10-9. What is the pH of a 0.025 M HONH2 solution?

A. 2.90 B. 4.82 C. 9.18 D. 9.91 E. 11.10

27. What is the value of Kb for the formate anion, HCOO-? Ka(HCOOH) = 2.1 10-4

A. -2.1 10-4 B. 2.1 10-4 C. 6.9 10-6 D. 4.8 10-11 E. 2.1 10-18

28. What is the value of Kb for the cyanide anion, CN-? Ka(HCN) = 6.2 10-10

A. 1.6 10-4 B. 1.6 10-5 C. 3.8 10-4 D. 3.8 10-5 E. 6.2 104

29. What is the pH of a 0.0100 M sodium benzoate solution? Kb (C7H5O2-) = 1.5 10-10

A. 0.38 B. 5.91 C. 8.09 D. 9.82 E. 13.62

30. What is the pH of a 0.010 M triethanolammonium chloride, (HOC2H2)3NHCl, solution? Kb, ((HOC2H2)3N) = 5.9 10-7

A. 2.75 B. 4.89 C. 9.11 D. 11.25 E. none of these choices is correct

31. Which of the following aqueous liquids will have the highest pH? A. 0.1 M CH3COOH, pKa = 4.7 B. 0.1 M CuCl2, pKa = 7.5 C. 0.1 M H3C6H5O7, pKa = 3.1 D. 0.1 M ZnCl2, pKa = 9.0 E. pure water

32. A solution is prepared by adding 0.10 mol of sodium fluoride, NaF, to 1.00 L of water. Which statement about the solution is correct?

A. The solution is basic. B. The solution is neutral. C. The solution is acidic. D. The concentrations of fluoride ions and sodium ions will be identical. E. The concentration of fluoride ions will be greater than the concentration of sodium ions.

33. A solution is prepared by adding 0.10 mol of potassium acetate, KCH3COO, to 1.00 L of water. Which statement about the solution is correct?

A. The solution is basic. B. The solution is neutral. C. The solution is acidic. D. The concentrations of potassium ions and acetate ions will be identical.

E. The concentration of acetate ions will be greater than the concentration of potassium ions. 34. A solution is prepared by adding 0.10 mol of iron(III) nitrate, Fe(NO3)3, to 1.00 L of water. Which

statement about the solution is correct? A. The solution is basic. B. The solution is neutral. C. The solution is acidic. D. The value of Ka for the species in solution must be known before a prediction can be made. E. The value of Kb for the species in solution must be known before a prediction can be made.

35. Ammonium chloride is used as an electrolyte in dry cells. Which of the following statements about a 0.10 M solution of NH4Cl, is correct?

A. The solution is weakly basic. B. The solution is strongly basic. C. The solution is neutral. D. The solution is acidic. E. The values for Ka and Kb for the species in solution must be known before a prediction can be

made. 36. A solution is prepared by adding 0.10 mol of lithium nitrate, LiNO3, to 1.00 L of water. Which statement

about the solution is correct? A. The solution is basic. B. The solution is neutral. C. The solution is weakly acidic. D. The solution is strongly acidic. E. The values for Ka and Kb for the species in solution must be known before a prediction can be

made. 37. Which one of the following substances will give an aqueous solution of pH < 7?

A. KI B. NH4Br C. Na2CO3 D. CH3COONa E. CH3OH

38. Which one of the following substances will give an aqueous solution of pH closest to 7? A. KNO3 B. CO2 C. NH4I D. NH3 E. CH3NH2

39. Which of the following is a Lewis base? A. BCl3 B. Cu2+ C. Cl- D. Mn2+ E. NH4+

40. Formic acid, HCOOH, is a weak acid with a pKa of 3.74. Draw up a reaction table for the reaction of 0.300 M formic acid with water, and calculate the pH of this solution.

41. The pH of a 0.200 M solution of the weak base pyridine, C5H5N, is 8.59. Draw up a reaction table for the reaction of 0.200 M pyridine with water, and calculate Kb.

42. Consider the reaction: BF3 + F- BF4- Can this ever be considered to be an acid-base reaction? Support your answer with appropriate arguments.

43. Which of the following aqueous mixtures would be a buffer system? A. HCl, NaCl B. HNO3, NaNO3 C. H3PO4, H2PO4- D. H2SO4, CH3COOH E. NH3, NaOH

44. Which, if any, of the following aqueous mixtures would be a buffer system? A. CH3COOH, NaH2PO4 B. H2CO3, HCO3- C. H2PO4-, HCO3- D. HSO4-, HSO3- E. None of these will be a buffer solution.

45. Equal volumes of the following pairs of solutions are mixed. Which pair will produce a buffer solution? A. 0.10 mol L-1 HCl and 0.05 mol L-1 NaOH B. 0.10 mol L-1 HCl and 0.15 mol L-1 NH3 C. 0.10 mol L-1 HCl and 0.05 mol L-1 NH3 D. 0.10 mol L-1 HCl and 0.20 mol L-1 CH3COOH E. 0.10 mol L-1 HCl and 0.20 mol L-1 NaCl

46. Which one of the following aqueous solutions, when mixed with an equal volume of 0.10 mol L-1 aqueous NH3, will produce a buffer solution?

A. 0.10 mol L-1 HCl B. 0.20 mol L-1 HCl C. 0.10 mol L-1 CH3COOH D. 0.050 mol L-1 NaOH E. 0.20 mol L-1 NH4Cl

47. Which of the following acids should be used to prepare a buffer with a pH of 4.5? A. HOC6H4OCOOH, Ka = 1.0 10-3 B. C6H4(COOH)2, Ka = 2.9 10-4 C. CH3COOH, Ka = 1.8 10-5 D. C5H5O5COOH-2, Ka = 4.0 10-6 E. HBrO, Ka = 2.3 10-9

48. An acetate buffer has a pH of 4.40. Which of the following changes will cause the pH to decrease? A. dissolving a small amount of solid sodium acetate B. adding a small amount of dilute hydrochloric acid C. adding a small amount of dilute sodium hydroxide D. dissolving a small amount of solid sodium chloride E. diluting the buffer solution with water

49. What will be the effect of adding 0.5 mL of 0.1 M NaOH to 100 mL of an acetate buffer in which [CH3COOH] = [CH3COO-] = 0.5 M?

A. The pH will increase slightly. B. The pH will increase significantly. C. The pH will decrease slightly. D. The pH will decrease significantly. E. Since it is a buffer solution, the pH will not be affected.

50. Buffer solutions with the component concentrations shown below were prepared. Which of them should have the lowest pH?

A. [CH3COOH] = 0.25 M, [CH3COO-] = 0.25 M B. [CH3COOH] = 0.75 M, [CH3COO-] = 0.75 M C. [CH3COOH] = 0.75 M, [CH3COO-] = 0.25 M D. [CH3COOH] = 0.25 M, [CH3COO-] = 0.75 M E. [CH3COOH] = 1.00 M, [CH3COO-] = 1.00 M

51. Buffer solutions with the component concentrations shown below were prepared. Which of them should have the highest pH?

A. [H2PO4-] = 0.50 M, [HPO42-] = 0.50 M B. [H2PO4-] = 1.0 M, [HPO42-] = 1.0 M C. [H2PO4-] = 1.0 M, [HPO42-] = 0.50 M D. [H2PO4-] = 0.50 M, [HPO42-] = 1.0 M E. [H2PO4-] = 0.75 M, [HPO42-] = 1.0 M

52. A buffer is prepared by adding 100 mL of 0.50 M sodium hydroxide to 100 mL of 0.75 M propanoic acid. Is this a buffer solution, and if so, what is its pH?

A. It is a buffer, pH > pKa of propanoic acid. B. It is a buffer, pH < pKa of propanoic acid. C. It is a buffer, pH = pKa of propanoic acid. D. It is a buffer, pH = pKb of sodium propanoate. E. Since sodium hydroxide is a strong base, this is not a buffer.

53. A solution is prepared by adding 100 mL of 0.2 M hydrochloric acid to 100 mL of 0.4 M sodium formate. Is this a buffer solution, and if so, what is its pH?

A. It is a buffer, pH > pKa of formic acid. B. It is a buffer, pH < pKa of formic acid. C. It is a buffer, pH = pKa of formic acid. D. It is a buffer, pH = pKb of sodium formate. E. Since hydrochloric acid is a strong acid, this is not a buffer.

54. What is the pH of a buffer that consists of 0.45 M CH3COOH and 0.35 M CH3COONa? Ka = 1.8 10-5

A. 4.49 B. 4.64 C. 4.85 D. 5.00 E. 5.52

55. What is the pH of a buffer that consists of 0.20 M NaH2PO4 and 0.40 M Na2HPO4? Ka = 6.2 10-8

A. 6.51 B. 6.91 C. 7.51 D. 7.90 E. 8.13

56. What is the pKa for the acid HA if a solution of 0.65 M HA and 0.85 M NaA has a pH of 4.75? A. < 4.00 B. 4.63 C. 4.87 D. 5.02 E. > 5.50

57. A formic acid buffer containing 0.50 M HCOOH and 0.50 M HCOONa has a pH of 3.77. What will the pH be after 0.010 mol of NaOH has been added to 100.0 mL of the buffer?

A. 3.67 B. 3.78 C. 3.81 D. 3.85 E. 3.95

58. A buffer is prepared by adding 1.00 L of 1.0 M HCl to 750 mL of 1.5 M NaHCOO. What is the pH of this buffer? Ka = 1.7 10-4

A. 2.87 B. 3.72 C. 3.82 D. 3.95 E. 4.66

59. At the equivalence point in an acid-base titration A. the [H3O+] equals the Ka of the acid. B. the [H3O+] equals the Ka of the indicator. C. the amounts of acid and base which have been combined are in their stoichiometric ratio. D. the pH is 7.0. E. the pH has reached a maximum.

60. When a strong acid is titrated with a strong base, the pH at the equivalence point A. is greater than 7.0. B. is equal to 7.0. C. is less than 7.0, but is not 3.5. D. is equal to the pKa of the acid. E. is equal to 3.5.

61. When a weak acid is titrated with a strong base, the pH at the equivalence point A. is greater than 7.0. B. is equal to 7.0. C. is less than 7.0. D. is equal to the pKa of the acid. E. is equal to 14.0 - pKb , where pKb is that of the base.

62. When a strong acid is titrated with a weak base, the pH at the equivalence point A. is greater than 7.0. B. is equal to 7.0. C. is less than 7.0. D. is equal to the pKa of the acid. E. is equal to the pKb of the base.

63. Which one of the following is the best representation of the titration curve which will be obtained in the titration of a weak acid (0.10 mol L-1) with a strong base of the same concentration?

A.

B.

C.

D.

E.

64. Which one of the following is the best representation of the titration curve which will be obtained in the

titration of a weak base (0.10 mol L-1) with HCl of the same concentration? A.

B.

C.

D.

E.

65. A 50.0-mL sample of 0.50 M HCl is titrated with 0.50 M NaOH. What is the pH of the solution after 28.0

mL of NaOH have been added to the acid? A. 0.85

B. 0.75 C. 0.66 D. 0.49 E. 3.8

66. A 20.0-mL sample of 0.30 M HBr is titrated with 0.15 M NaOH. What is the pH of the solution after 40.3 mL of NaOH have been added to the acid?

A. 2.95 B. 3.13 C. 10.87 D. 11.05 E. 13.14

67. A 25.0-mL sample of 0.35 M HCOOH is titrated with 0.20 M KOH. What is the pH of the solution after 25.0 mL of KOH has been added to the acid? Ka = 1.77 10-4

A. 4.00 B. 3.88 C. 3.63 D. 3.51 E. 3.47

68. Which one of the following is the best representation of the titration curve which will be obtained in the titration of a weak diprotic acid H2A (0.10 mol L-1) with a strong base of the same concentration?

A.

B.

C.

D.

E.

69. What volume of 0.500 M H2SO4 is needed to react completely with 20.0 mL of 0.400 M LiOH?

A. 4.00 mL B. 8.00 mL C. 12.5 mL D. 16.0 mL E. 32.0 mL

70. A change in pH will significantly affect the solubility of which, if any, of the following compounds? A. BaF2 B. CuCl C. CuBr D. AgI E. None of the solubilities will be significantly affected.

71. Write the ion product expression for magnesium fluoride, MgF2. A. B. C.

D.

E.

72. The solubility of lead(II) chloride is 0.45 g/100 mL of solution. What is the Ksp of PbCl2?

A. 4.9 10-2 B. 1.7 10-5 C. 8.5 10-6 D. 4.2 10-6 E. < 1.0 10-6

73. Calculate the solubility of barium carbonate, BaCO3, in pure water. Ksp = 2.0 10-9 A. 1.3 10-3 M B. 3.2 10-5 M C. 2.2 10-5 M

D. 4.5 10-5 M E. 4.0 10-18 M

74. Calculate the solubility of strontium fluoride, SrF2, in pure water. Ksp = 2.6 10-9 A. 1.4 10-3 M B. 3.4 10-4 M C. 8.7 10-4 M D. 5.l 10-5 M E. < 1.0 10-5 M

75. Which of the following substances has the greatest solubility in water? A. MgCO3, Ksp = 3.5 10-8 B. NiCO3, Ksp = 1.3 10-7 C. AgIO3, Ksp = 3.1 10-8 D. CuBr, Ksp = 5.0 10-9 E. AgCN, Ksp = 2.2 10-16

76. Calculate the solubility of magnesium sulfate, MgSO4, when placed into a 0.10 M MgCl2 solution. Ksp = 5.9 10-3

A. 4.2 10-2 M B. 5.9 10-2 M C. 7.7 10-2 M D. 3.5 10-5 M E. 3.5 10-6 M

77. Calculate the solubility of lead(II) iodide, PbI2, in 0.025 M KI. Ksp = 7.9 10-9 A. 4.5 10-2 M B. 2.8 10-2 M C. 8.9 10-5 M D. 5.0 10-5 M E. 1.3 10-5 M

78. A lab technician adds 0.015 mol of KOH to 1.00 L of 0.0010 M Ca(NO3)2. Ksp = 6.5 10-6 for Ca(OH)2. Which of the following statements is correct?

A. Calcium hydroxide precipitates until the solution is saturated. B. The solution is unsaturated and no precipitate forms. C. The concentration of calcium ions is reduced by the addition of the hydroxide ions. D. One must know Ksp for calcium nitrate to make meaningful predictions on this system. E. The presence of KOH will raise the solubility of Ca(NO3)2.

79. A lab technician adds 0.20 mol of NaF to 1.00 L of 0.35 M cadmium nitrate, Cd(NO3)2. Which of the following statements is correct? Ksp = 6.44 10-3 for CdF2

A. Cadmium fluoride precipitates until the solution is saturated. B. The solution is unsaturated and no precipitate forms. C. The solubility of cadmium fluoride is increased by the presence of additional fluoride ions. D. One must know Ksp for cadmium nitrate to make meaningful predictions on this system. E. The presence of NaF will raise the solubility of Cd(NO3)2.

80. The lab technician Anna Lytic adds 2.20 mol KOH to 1.00 L of 0.5 M Al(NO3)3. What is the concentration of aluminum ions after the aluminum nitrate has reacted with the potassium hydroxide? Kf = 3.0 1033 for Al(OH)4-

A. 1.8 10-7 M B. 9.l 10-18 M C. 1.0 10-31 M

D. 3.3 10-34 M E. 7.l 10-36 M

81. Which of the following is true for pure oxygen gas, O2(g) at 25C? A. H f > 0 B. H f < 0 C. G f > 0 D. G f < 0 E. S > 0

82. Which of the following results in a decrease in the entropy of the system? A. O2(g), 300 K O2(g), 400 K B. H2O(s), 0C H2O(l), 0C C. N2(g), 25C N2(aq), 25C D. NH3(l), -34.5C NH3(g), -34.5C E. 2H2O2(g) 2H2O(g) + O2(g)

83. When a sky diver free-falls through the air, the process is A. non-spontaneous because he is accelerating due to the force applied by gravity. B. non-spontaneous because he is losing potential energy. C. non-spontaneous because he had planned the jump for two weeks. D. spontaneous. E. in equilibrium.

84. Which, if any, of the following processes is spontaneous under the specified conditions? A. H2O(l) H2O(s) at 25C B. CO2(s) CO2(g) at 0C C. 2H2O(g) 2H2(g) + O2(g) D. C(graphite) C(diamond) at 25C and 1 atm pressure E. None of these is spontaneous.

85. Which relationship or statement best describes S for the following reaction? Pb(s) + Cl2(g) PbCl2(s)

A. S 0 B. S < 0 C. S > 0 D. S = H/T E. More information is needed to make a reasonable prediction.

86. Which relationship or statement best describes S for the following reaction? 2H2S(g) + 3O2(g) 2H2O(g) + 2SO2(g)

A. S 0 B. S < 0 C. S > 0 D. S = H/T E. More information is needed to make a reasonable prediction.

87. Which relationship or statement best describes S for the following reaction? 2NH3(g) + 2ClF3(g) 6HF(g) + N2(g) + Cl2(g)

A. S 0 B. S < 0

C. S > 0 D. S = H/T E. More information is needed to make a reasonable prediction.

88. Which relationship or statement best describes S for the following reaction? BaCl2(aq) + Na2SO4(aq) BaSO4(s) + 2NaCl(aq)

A. S 0 B. S < 0 C. S > 0 D. S = H/T E. More information is needed to make a reasonable prediction.

89. Calculate Sfor the reaction SiCl4(g) + 2Mg(s) 2MgCl2(s) + Si(s)

Substance: SiCl4(g) Mg(s) MgCl2(s) Si(s) S(J/Kmol): 330.73 32.68 89.62 18.83

A. -254.96 J/K B. -198.02 J/K C. 198.02 J/K D. 254.96 J/K E. 471.86 J/K

90. Calculate Sfor the reaction 4Cr(s) + 3O2(g) 2Cr2O3(s)

Substance: Cr(s) O2(g) Cr2O3(s) S(J/Kmol): 23.77 205.138 81.2

A. -548.1 J/K B. -147.7 J/K C. 147.7 J/K D. 310.1 J/K E. 548.1 J/K

91. For a chemical reaction to be spontaneous only at high temperatures, which of the following conditions must be met?

A. S > 0, H > 0 B. S > 0, H < 0 C. S < 0, H < 0 D. S < 0, H > 0 E. G > 0

92. For a chemical reaction to be spontaneous only at low temperatures, which of the following conditions must be met?

A. S> 0, H > 0 B. S > 0, H < 0 C. S < 0, H < 0 D. S < 0, H > 0 E. G > 0

93. For a chemical reaction to be spontaneous at all temperatures, which of the following conditions must be met?

A. S > 0, H > 0 B. S > 0, H < 0 C. S < 0, H < 0 D. S < 0, H > 0 E. It is not possible for a reaction to be spontaneous at all temperatures.

94. For a chemical reaction to be non-spontaneous at any temperature, which of the following conditions must be met?

A. S > 0, H > 0 B. S > 0, H < 0 C. S < 0, H < 0 D. S < 0, H > 0 E. All reactions are spontaneous at some temperature.

95. Calculate G for the reaction SiCl4(g) + 2Mg(s) 2MgCl2(s) + Si(s)

Substance: SiCl4(g) Mg(s) MgCl2(s) Si(s) G f (kJ/mol): -616.98 0 -591.79 0

A. 566.60 kJ B. 50.38 kJ C. 25.19 kJ D. -25.19 kJ E. -566.60 kJ

96. Calculate G for the combustion of propane. C3H8(g) + 5O2(g) 3CO2(g) + 4H2O(g)

Substance: C3H8(g) O2(g) CO2(g) H2O(g) G f (kJ/mol): -24.5 0 -394.4 -228.6

A. -2073.1 kJ B. -1387.3 kJ C. -598.5 kJ D. 598.5 kJ E. 2073.1 kJ

97. Use the given data at 298 K to calculate G for the reaction 2Cl2(g) + SO2(g) SOCl2(g) + Cl2O(g)

Substance: Cl2(g) SO2(g) SOCl2(g) Cl2O(g) H f (kJ/mol): 0 -296.8 -212.5 80.3 S(J/Kmol): 223.0 248.1 309.77 266.1

A. 129.3 kJ B. 133.6 kJ

C. 196.0 kJ D. 199.8 kJ E. 229.6 kJ

98. The temperature at which the following process reaches equilibrium at 1.0 atm is the normal boiling point of hydrogen peroxide. H2O2(l) H2O2(g) Use the following thermodynamic information at 298 K to determine this temperature.

Substance: H2O2(l) H2O2(g) H f (kJ/mol): -187.7 -136.3 G f (kJ/mol): -120.4 -105.6 S (J/Kmol): 109.6 232.7

A. 120C B. 144C C. 196C D. 418C E. 585C

99. The temperature at which the following process reaches equilibrium at 1.0 atm is the normal melting point for phosphoric acid. H3PO4(s) H3PO4(l) Use the following thermodynamic data at 298 K to determine this temperature.

Substance: H3PO4(s) H3PO4(l) H f (kJ/mol): -1284.4 -1271.7 G f (kJ/mol): -1124.3 -1123.6 S(J/Kmol): 110.5 150.8

A. 286 K B. 305 K C. 315 K D. 347 K E. 3170 K

100. Consider the figure below which shows G for a chemical process plotted against absolute temperature. From this plot, it is reasonable to conclude that:

A. H > 0, S > 0 B. H > 0, S < 0 C. H < 0, S > 0

D. H < 0, S < 0 E. none of these choices is correct

101. Iron(III) oxide can be reduced by carbon monoxide. Fe2O3(s) + 3CO(g) 2Fe(s) + 3CO2(g) Use the following thermodynamic data at 298 K to determine the equilibrium constant at this temperature.

Substance: Fe2O3(s) CO(g) Fe(s) CO2(g) H f (kJ/mol): -824.2 -110.5 0 -393.5 G f (kJ/mol): -742.2 -137.2 0 -394.4 S(J/Kmol): 87.4 197.7 27.78 213.7

A. 7.0 10-6 B. 1.3 10-3 C. 2.2 104 D. 1.4 105 E. > 2.0 105

102. Calculate the equilibrium constant at 25C for the reaction of methane with water to form carbon dioxide and hydrogen. The data refer to 25C. CH4(g) + 2H2O(g) CO2(g) + 4H2(g)

Substance: CH4(g) H2O(g) CO2(g) H2(g) H f (kJ/mol): -74.87 -241.8 -393.5 0 G f (kJ/mol): -50.81 -228.6 -394.4 0 S (J/Kmol): 186.1 188.8 213.7 130.7

A. 8.2 1019 B. 0.96 C. 0.58 D. 1.2 10-20 E. 1.4 10-46

103. The reaction of methane with water to form carbon dioxide and hydrogen is non-spontaneous at 298 K. At what temperature will this system make the transition from non-spontaneous to spontaneous? The data refer to 298 K. CH4(g) + 2H2O(g) CO2(g) + 4H2(g)

Substance: CH4(g) H2O(g) CO2(g) H2(g) H f (kJ/mol): -74.87 -241.8 -393.5 0 G f (kJ/mol): -50.81 -228.6 -394.4 0 S(J/Kmol): 186.1 188.8 213.7 130.7

A. 658 K B. 683 K C. 955 K D. 1047 K E. 1229 K

104. Use the thermodynamic data at 298 K below to determine the Ksp for barium carbonate, BaCO3 at this temperature.

Substance: Ba2+(aq) CO32-(aq) BaCO3(s) H f (kJ/mol): -538.36 -676.26 -1219 G f (kJ/mol): -560.7 -528.1 -1139 S(J/Kmol): 13 -53.1 112

A. 5.86 B. 6.30 108 C. 1.59 10-9 D. 5.47 10-21 E. 2.18 10-27

105. The formation constant for the reaction Ag+(aq) + 2NH3(aq) Ag(NH3)2+(aq) is Kf = 1.7 107 at 25C. What is G at this temperature?

A. -1.5 kJ B. -3.5 kJ C. -18 kJ D. -23 kJ E. -41 kJ

Exam2-chem220 KEY Created: 8:39:48 AM MST

1. (p. 772) B 2. (p. 772) B 3. (p. 772) C 4. (p. 772) E 5. (p. 772) C 6. (p. Sec. 18.1, 18.2) D 7. (p. Sec. 18.1, 18.2) B 8. (p. 776) B 9. (p. 776) A 10. (p. 776) E 11. (p. 776) C 12. (p. 776) C 13. (p. 776) D 14. (p. 776) C 15. (p. 779) D 16. (p. 779) D 17. (p. 779) E 18. (p. 780) B 19. (p. 783) D 20. (p. 783) D 21. (p. 784) A 22. (p. 784) C 23. (p. 785) C 24. (p. 787) B 25. (p. 790) A 26. (p. 790) C 27. (p. 792) D 28. (p. 792) B 29. (p. 792) C 30. (p. 792) B 31. (p. 795) D 32. (p. 797) A 33. (p. 797) A 34. (p. 795) C 35. (p. 796) D 36. (p. 796) B 37. (p. Sec. 18.8) B 38. (p. Sec. 18.8) A 39. (p. 801) C 40. (p. 784) HCOOH(aq) + H2O(l) HCOO-(aq) + H3O+(aq) Initial conc, M 0.300 - 0 10-7 Change in conc, M -x - x x Equilibrium conc, M 0.300 - x - x 10-7 + x Assuming 0.300 - x 0.300 and 10-7 + x x, the pH is 2.13 41. (p. 783) C5H5N(l) + H2O(l) C5H5NH+(aq) + OH-(aq) Initial conc, M 0.300 - 0 10-7 Change in conc, M -x - x x

Equilibrium conc, M 0.200 - x - x 10-7 + x pH = 10.95 42. (p. 801) Yes, according to Lewis, this is an acid-base reaction. The Lewis acid, BF3, accepts a pair of electrons from the base, F-. 43. (p. 816) C 44. (p. 816) B 45. (p. 816) B 46. (p. 816) E 47. (p. 822) C 48. (p. 818) B 49. (p. 818) A 50. (p. 820) C 51. (p. 820) D 52. (p. 823) A 53. (p. 823) C 54. (p. 820) B 55. (p. 820) C 56. (p. 820) B 57. (p. 818) E 58. (p. 823) A 59. (p. 825) C 60. (p. 826) B 61. (p. 827) A 62. (p. 830) C 63. (p. 827) B 64. (p. 830) D 65. (p. 825) A 66. (p. 825) C 67. (p. 828) B 68. (p. 831) A 69. (p. 831) B 70. (p. 839) A 71. (p. 833) B 72. (p. 835) B 73. (p. 836) D 74. (p. 836) C 75. (p. 837) B 76. (p. 838) A 77. (p. 838) E 78. (p. 841) B 79. (p. 841) A 80. (p. 841) C 81. (p. 871) E 82. (p. 871) C 83. (p. 870) D 84. (p. 870) B 85. (p. 871) B 86. (p. 875) B 87. (p. 875) C 88. (p. 871) B 89. (p. 876) B 90. (p. 876) A

91. (p. 887) A 92. (p. 887) C 93. (p. 887) B 94. (p. 887) D 95. (p. 884) E 96. (p. 884) A 97. (p. 883) D 98. (p. 888) B 99. (p. 888) C 100. (p. 887) A 101. (p. 892) D 102. (p. 892) D 103. (p. 888) C 104. (p. 892) C 105. (p. 892) E