Chapter 14: Acids and Bases
1. For the equilibrium that exists in an aqueous solution of nitrous acid (HNO2, a weak acid),
the equilibrium constant expression is:
A)
K =
B)
K =
C)
K = [H+][NO2–]
D)
K =
E)
none of these
2. Which of the following is a conjugate acid/base pair?
A)
HCl/OCl–
B)
H2SO4/SO42–
C)
NH4+/NH3
D)
H3O+/OH–
E)
more than one of these
3. The equilibrium constant for the reaction A– + H+ HA is called:
A)
Ka
B)
Kb
C)
D)
E)
KwKa
4. What is the equilibrium constant for the following reaction? N3– + H3O+ HN3 + H2O
The Ka value for HN3 = 1.9 10–5.
A)
5.3 10–10
B)
1.9 10–9
C)
1.9 10–5
D)
5.3 104
E)
1.9 109
5. The hydrogen sulfate or bisulfate ion HSO4– can act as either an acid or a base in water
solution. In which of the following equations does HSO4– act as an acid?
A)
HSO4– + H2O → H2SO4 + OH–
B)
HSO4– + H3O+ → SO3 + 2H2O
C)
HSO4– + OH– → H2SO4 + O2–
D)
HSO4– + H2O → SO42– + H3O+
E)
none of these
6. Which of the following is the equilibrium constant expression for the dissociation of the
weak acid HOCl?
A)
K =
B)
K = [H+][OCl–]
C)
K =
D)
K =
E)
none of these
7. Consider the reaction HNO2(aq) + H2O(l) H3O+(aq) + NO2–(aq). Which species is a
conjugate base?
A)
HNO2(aq)
B)
H2O(l)
C)
H3O+(aq)
D)
NO2–(aq)
E)
two of these
8. In which of the following reactions does the H2PO4– ion act as an acid?
A)
H3PO4 + H2O → H3O+ + H2PO4–
B)
H2PO4– + H2O → H3O+ + HPO42–
C)
H2PO4– + OH– → H3PO4 + O2–
D)
The ion cannot act as an acid.
E)
Two of these.
Consider the following reactions:
a)
Al3+ + 6H2O Al(OH2)63+
b)
Al(OH2)63+ Al(OH)(OH2)52+ + H+
c)
OCl– + H2O HOCl + OH–
d)
CN– + H+ HCN
e)
9. Which is associated with the definition of Ka?
A)
a
B)
b
C)
c
D)
d
E)
e
10. Which is associated with the definition of Kb?
A)
a
B)
b
C)
c
D)
d
E)
e
11. Using the following Ka values, indicate the correct order of base strength.
HNO2
Ka = 4.0 10–4
HF
Ka = 7.2 10–4
HCN
Ka = 6.2 10–10
A)
CN– > NO2– > F– > H2O > Cl–
B)
Cl– > H2O > F– > NO2– > CN–
C)
CN– > F– > NO2– > Cl– > H2O
D)
H2O > CN– > NO2– > F– > Cl–
E)
none of these
12. The equilibrium constants (Ka) for HCN and HF in H2O at 25°C are 6.2 10–10 and
7.2 10–4, respectively. The relative order of base strengths is:
A)
F– > H2O > CN–
B)
H2O > F– > CN–
C)
CN– > F– > H2O
D)
F– > CN– > H2O
E)
none of these
13. Given the following acids and Ka values:
HClO4
HOAc
HCN
HF
1 107
1.76 10–5
4.93 10–10
3.53 10–4
What is the order of increasing base strength?
A)
CN–, F–, OAc–, ClO4–
B)
CN–, OAc–, F–, ClO4–
C)
CN–, ClO4–, F–, OAc–
D)
ClO4–, OAc–, CN–, F–
E)
ClO4–, F–, OAc–, CN–
14. Which of the following is not true for a solution at 25°C that has a hydroxide concentration
of 2.5 10–6 M?
A)
Kw = 1 10–14
B)
The solution is acidic.
C)
The solution is basic.
D)
The [H+] is 4.0 10–9 M.
E)
The Kw is independent of what the solution contains.
Consider the reaction HOCl + F– HF + OCl–
15. Given that Ka for HOCl is 3.5 10–8 and the Ka for HF is 7.2 10–4 (both at 25°C), which of
the following is true concerning K for the above reaction at 25°C?
A)
K is greater than 1.
B)
K is less than 1.
C)
K is equal to 1.
D)
Cannot be determined with the above information.
E)
None of these (A-D).
16. Assuming that the value for K in the above reaction is greater than 1, this means that HF is a
stronger acid than HOCl.
17. HA and HB are both weak acids in water, and HA is a stronger acid than HB. Which of the
following statements is correct?
A)
A– is a stronger base than B–, which is a stronger base than H2O, which is a
stronger base than Cl–.
B)
B– is a stronger base than A–, which is a stronger base than H2O, which is a
stronger base than Cl–.
C)
B– is a stronger base than A–, which is a stronger base than Cl–, which is a stronger
base than H2O.
D)
Cl– is a stronger base than A–, which is a stronger base than B–, which is a stronger
base than H2O.
E)
None of these (A-D) is correct.
18. True or false: The species Cl– is not a good base in aqueous solution.
A)
True. This is because Cl– is the conjugate base of a weak acid.
B)
False. The species Cl– is a good base in aqueous solution because it is the
conjugate base of a strong acid.
C)
True. This is because Cl– is a good proton donor.
D)
False. The species Cl– is a good base in aqueous solution because of its high
electronegativity.
E)
True. This is because water has a stronger attraction for protons than does Cl–.
19. The autoionization of water, as represented by the below equation, is known to be
endothermic. Which of the following correctly states what occurs as the temperature of
water is raised? H2O(l) + H2O(l) H3O+(aq) + OH–(aq)
A)
The pH of the water does not change, and the water remains neutral.
B)
The pH of the water decreases, and the water becomes more acidic.
C)
The pH of the water decreases, and the water remains neutral.
D)
The pH of the water increases, and the water becomes more acidic.
E)
The pH of the water increases and the water remains neutral.
The following three equations represent equilibria that lie far to the right.
HNO3(aq) + CN–(aq) HCN(aq) + NO3–(aq)
HCN(aq) + OH–(aq) H2O(l) + CN–(aq)
H2O(l) + CH3O–(aq) CH3OH(aq) + OH–(aq)
20. Identify the strongest acid.
A)
HCN
B)
HNO3
C)
H2O
D)
OH–
E)
CH3OH
21. Identify the strongest base.
A)
CH3O–
B)
CH3OH
C)
CN–
D)
H2O
E)
NO3–
22. A solution in which the pOH is 12.1 would be described as
A)
very acidic
B)
slightly acidic
C)
neutral
D)
very basic
E)
slightly basic
23. Calculate the [H+] in a solution that has a pH of 9.88.
A)
4.1 M
B)
9.9 M
C)
7.6 10–5 M
D)
1.3 10–10 M
E)
none of these
24. Calculate the [H+] in a solution that has a pH of 2.73.
A)
2.7 M
B)
11.3 M
C)
1.9 10–3 M
D)
5.4 10–12 M
E)
none of these
25. Calculate the [H+] in a solution that has a pH of 8.73.
A)
1.9 10–9 M
B)
5.4 10–6 M
C)
8.7 10–9 M
D)
9.4 10–1 M
E)
7.2 10–1 M
26. The pH of a solution at 25°C in which [OH–] = 3.9 10–5 M is:
A)
4.41
B)
3.90
C)
9.59
D)
4.80
E)
none of these
27. In deciding which of two acids is the stronger, one must know:
A)
the concentration of each acid solution
B)
the pH of each acid solution
C)
the equilibrium constant of each acid
D)
all of the above
E)
both A and C must be known
28. Solid calcium hydroxide is dissolved in water until the pH of the solution is 11.44. The
hydroxide ion concentration [OH–] of the solution is:
A)
3.6 10–12 M
B)
5.5 10–3 M
C)
2.8 10–3 M
D)
1.4 10–3 M
E)
none of these
29. As water is heated, its pH decreases. This means that:
A)
The water is no longer neutral.
B)
[H+] > [OH–]
C)
[OH–] > [H+]
D)
A and B are correct.
E)
None of these.
30. As water is heated, its pH decreases. This means that:
A)
The water is no longer neutral.
B)
The Kw value is decreasing.
C)
The water has a lower [OH–] than cooler water.
D)
The dissociation of water is an endothermic process.
E)
None of these.
31. At 65°C, the ion-product constant of water, Kw, is 1.20 10–13. The pH of pure water at
65°C is:
A)
7.000
B)
6.560
C)
5.880
D)
6.460
E)
none of these
32. What is the pOH of pure water at 65oC? (Kw at 65oC = 1.20 10–13)
A)
7.540
B)
7.000
C)
14.000
D)
12.921
E)
6.460
33. Which of the following indicates the most basic solution?
A)
[H+] = 1 10–10 M
B)
pOH = 6.7
C)
[OH–] = 7 10–5 M
D)
pH = 4.2
E)
At least two of the solutions are equally basic.
34. Calculate the pH of 0.203 M HNO3(aq).
A)
0.693
B)
2.030
C)
–1.140
D)
13.797
E)
1.595
35. Calculate the pOH of a 4.9 M solution of HCl.
A)
–0.69
B)
13.31
C)
14.69
D)
0.69
E)
–0.96
36. You have 100.0 mL of a solution of hydrochloric acid that has a pH of 3.00. You add 100.0
mL of water to this solution. What is the resulting pH of the solution?
A)
The pH = 5.00 (the average of 3.00 and 7.00).
B)
The pH = 10.00 (3.00 + 7.00 = 10.00).
C)
The pH = 3.00 (water is neutral and does not affect the pH).
D)
None of the above is correct, but the pH must be greater than 3.00.
E)
None of the above is correct, but the pH must be less than 3.00.
37. What volume of water must be added to 11.1 mL of a pH 2.0 solution of HNO3 in order to
change the pH to 4.0?
A)
11.1 mL
B)
89 mL
C)
110 mL
D)
1.10 103 mL
E)
28 mL
38. Calculate the pH of a 0.031 M strong acid solution.
A)
–1.51
B)
1.51
C)
12.49
D)
15.51
E)
none of these
39. For nitrous acid, HNO2, Ka = 4.0 10–4. Calculate the pH of 0.27 M HNO2.
A)
1.98
B)
0.57
C)
3.97
D)
12.02
E)
none of these
40. The pKa of HOCl is 7.5. Calculate the pH of a 0.31 M solution of HOCl.
A)
7.50
B)
6.50
C)
4.00
D)
10.00
E)
0.31
41. For weak acid, HX, Ka = 6.9 10–6. Calculate the pH of a 0.13 M solution of HX.
A)
0.89
B)
3.02
C)
6.05
D)
10.98
E)
none of these
42. Calculate the pH of a 0.13 M solution of HOCl, Ka = 3.5 10–8.
A)
4.17
B)
8.34
C)
9.83
D)
1.00
E)
3.76
43. Calculate the pOH of a 0.12 M solution of acetic acid (Ka = 1.8 10–5).
A)
2.83
B)
8.33
C)
5.67
D)
11.17
E)
1.91
44. Acetic acid, (HC2H3O2) is a weak acid (Ka = 1.8 10–5). Calculate the pH of a 15.1 M
HC2H3O2 solution.
A)
–1.18
B)
3.57
C)
1.78
D)
1.18
E)
12.22
45. Calculate the [H+] in a 0.068 M solution of HCN, Ka = 6.2 10–10.
A)
1.0 10–7 M
B)
6.5 10–6 M
C)
4.2 10–11 M
D)
1.3 10–5 M
E)
none of these
46. Determine the concentration of a solution of the weak acid HClO2 (Ka = 1.10 10–2) if it has
a pH of 1.075.
A)
0.644 M
B)
0.0841 M
C)
7.65 M
D)
12.9 M
E)
1.287 M
47. How many moles of benzoic acid, a monoprotic acid with Ka = 6.4 10–5, must be dissolved
in 250. mL of H2O to produce a solution with pH = 2.04?
A)
1.3
B)
0.00228
C)
0.32
D)
36
E)
none of these
48. What concentration of acetic acid (Ka = 1.80 10–5) has the same pH as that of 5.33 10–3
M HCl?
A)
17.2 M
B)
12.4 M
C)
1.58 M
D)
5.33 10–3 M
E)
none of these
49. Calculate the pH of the following aqueous solution:
0.66 M HOCl (pKa = 7.46)
A)
10.18
B)
3.82
C)
7.64
D)
6.36
E)
none of these
50. Hypobromous acid, HOBr, has an acid dissociation constant of 2.5 10–9 at 25°C. What is
the pOH of a 0.075 M HOBr solution?
A)
2.80
B)
4.27
C)
4.86
D)
9.14
E)
11.20
51. In a solution prepared by dissolving 0.100 mole of propanoic acid in enough water to make
1.00 L of solution, the pH is observed to be 2.832. The Ka for propanoic acid (HC3H5O2) is:
A)
1.47 10–3
B)
2.20 10–5
C)
1.49 10–2
D)
4.55 10–10
E)
none of these
52. The pH of a 0.118 M solution of an aqueous weak acid (HA) is 3.20. The Ka for the weak
acid is:
A)
5.4 10–3
B)
4.0 10–7
C)
3.4 10–6
D)
3.2
E)
none of these
53. Saccharin is a monoprotic acid. If the pH of a 4.41 10–3 M solution of this acid is 2.53,
what is the Ka of saccharin?
A)
8.7 10–6
B)
2.0 10–3
C)
6.0 10–3
D)
2.9 10–3
E)
none of these
54. When 2.5 10–2 mol of nicotinic acid (a monoprotic acid) is dissolved in 350 mL of water,
the pH is 3.05. Calculate the Ka of nicotinic acid.
A)
1.3 10–2
B)
1.1 10–5
C)
7.1 10–2
D)
3.3 10–5
E)
none of these
55. Approximately how much water should be added to 10.0 mL of 11.1 M HCl so that it has
the same pH as 0.90 M acetic acid (Ka = 1.8 10–5)?
A)
28 mL
B)
276 mL
C)
3 L
D)
28 L
E)
276 L
56. The pH of a 0.17 M solution of a weak monoprotic acid, HA, is 2.92. Calculate the Ka for
this acid.
A)
0.17
B)
1.2 10–3
C)
7.1 10–3
D)
8.6 10–6
E)
7.3 10–11
57. A monoprotic weak acid when dissolved in water is 0.75% dissociated and produces a
solution with a pH of 3.11. Calculate the Ka of the acid.
A)
7.6 10–3
B)
1.0 10–1
C)
5.9 10–6
D)
Need to know the initial concentration of the acid.
E)
None of these.
58. A 8.5 10–3 M solution of a weak acid is 4.6% dissociated at 25°C. In a 8.5 10–4 M
solution, the percentage of dissociation would be
A)
the same
B)
> 4.6%
C)
< 4.6%
D)
zero
E)
need to know the Ka of the acid to answer this
59. A solution of 2.9 M weak acid is 0.52% ionized. What is the Ka value of this acid?
A)
7.9 10–5
B)
1.5
C)
1.5 10–2
D)
5.2 10–3
E)
none of these
60. A solution of 8.01 M formic acid (HCOOH) is 0.47% ionized. What is the Ka value of
formic acid?
A)
3.8 10–2
B)
1.8 10–4
C)
4.7 10–3
D)
3.8
E)
more data is needed
61. If an acid, HA, is 14.7% dissociated in a 1.0 M solution, what is the Ka for this acid?
A)
1.7 10–1
B)
2.5 10–2
C)
1.5 10–1
D)
3.9 101
E)
none of these
62. Determine the percent dissociation of a 0.18 M solution of hypochlorous acid, HClO. The Ka
for the acid is 3.5 10–8.
A)
3.5 10–6 %
B)
6.3 10–9 %
C)
7.9 10–3 %
D)
4.4 10–2 %
E)
1.1 10–2 %
63. The following question refers to a solution that contains 1.59 M hydrofluoric acid, HF
(Ka = 7.2 10–4), and 3.00 M hydrocyanic acid, HCN (Ka = 6.2 10–10).
What is the pH of this mixture of weak acids?
A)
1.47
B)
2.94
C)
4.50
D)
9.01
E)
12.53
64. The following question refers to a solution that contains 1.99 M hydrofluoric acid, HF
(Ka = 7.2 10–4), and 3.00 M hydrocyanic acid, HCN (Ka = 6.2 10–10).
Determine the [CN–] at equilibrium.
A)
1.9 10–9 M
B)
3.8 10–2 M
C)
4.9 10–8 M
D)
6.2 10–10 M
E)
none of these
65. Consider a 0.70 M solution of HOCl. If the molarity was decreased to 0.3 M, which of the
following statements would be true?
A)
The percent dissociation would not change.
B)
The percent dissociation would increase.
C)
The percent dissociation would decrease.
D)
The equilibrium constant would stay the same.
E)
Two of these.
66. Consider a solution made by mixing HCN (Ka = 6.2 10–10) with HC2H3O2 (Ka = 1.8 10–
5) in aqueous solution. What are the major species in solution?
A)
H+, CN–, H+, C2H3O2–, H2O
B)
HCN, H+, C2H3O2–, H2O
C)
H+, CN–, HC2H3O2, H2O
D)
H+, CN–, H+, C2H3O2–, OH–, H2O
E)
HCN, HC2H3O2, H2O
67. Which of the following solutions contains the strongest acid?
A)
5.00 M HCN (Ka = 6.2 10–10)
B)
3.50 M H2C6H6O6 (Ka1 = 7.9 10–5, Ka2 = 1.6 10–12).
C)
2.50 M HC2H3O2 (Ka = 1.8 10–5)
D)
4.00 M HOCl (Ka = 3.5 10–8)
E)
1.00 M HF (Ka = 7.2 10–4)
68. Which of the following statements are true?
A)
The pH of a strong acid is always lower than the pH of a weak acid.
B)
The pH of a solution can never be negative.
C)
For a conjugate acid-base pair, Ka = 1/Kb.
D)
At least two of the statements A-C are true.
E)
All of the statements A-C are false.
69. Which of the following reactions is associated with the definition of Kb?
A)
Zn(OH2)62+ [Zn(OH2)5OH]+ + H+
B)
CN– + H+ HCN
C)
F– + H2O HF + OH–
D)
Cr3+ + 6H2O Cr(OH2)63+
E)
none of these
70. Calculate the pH of a 0.02 M solution of KOH.
A)
1.7
B)
15.7
C)
14.0
D)
12.3
E)
cannot calculate answer unless a volume is given
71. Calculate the pH of a 0.51 M solution of KOH.
A)
14.00
B)
13.71
C)
0.29
D)
0.51
E)
none of these
72. Calculate the pH of a 0.059 M solution of Ca(OH)2.
A)
13.07
B)
12.77
C)
0.93
D)
1.23
E)
none of these
73. Calculate the pOH of a 0.32 M solution of Ba(OH)2.
A)
0.49
B)
0.19
C)
13.81
D)
13.51
E)
none of these
74. A 0.372-g sample of NaOH(s) is added to enough water to make 250.0 mL of solution. The
pH of this solution is:
A)
1.429
B)
0.429
C)
11.968
D)
12.571
E)
none of these
75. Calculate the pH of a 2.3 10–3 M KOH solution.
A)
2.64
B)
12.36
C)
11.36
D)
1.64
E)
10.36
76. Calculate the pH of a 2.28 M solution of NaOH.
A)
0.358
B)
13.642
C)
14.358
D)
2.28
E)
none of these