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18) HZ is a weak acid. An aqueous solution of HZ is prepared by dissolving 0.020 mol of HZ in sufficient
water to yield 1.0 L of solution. The pH of the solution was 4.93 at 25.0 °C. The Ka of HZ is ________.
A) 1.2 × 10-5
B) 6.9 × 10-9
C) 1.4 × 10-10
D) 9.9 × 10-2
E) 2.8 × 10-12
19) The pH of a 0.55 M aqueous solution of hypobromous acid, HBrO, at 25.0 °C is 4.48. What is the value
of Ka for HBrO?
A) 2.0 × 10-9
B) 1.1 × 10-9
C) 6.0 × 10-5
D) 3.3 × 10-5
E) 3.0 × 104
20) The pH of a 0.25 M aqueous solution of hydrofluoric acid, HF, at 25.0 °C is 2.03. What is the value of
Ka for HF?
A) 2.0 × 10-9
B) 1.1 × 10-9
C) 6.0 × 10-5
D) 3.5 × 10-4
E) none of the above
21) The pH of a 0.60 M aqueous solution of formic acid, HCHO2, at 25.0 °C is 1.98. What is the value of
Ka for formic acid?
A) 2.0 × 10-5
B) 1.8 × 10-4
C) 6.0 × 10-5
D) 3.5 × 10-4
E) none of the above
22) A 0.15 M aqueous solution of the weak acid HA at 25.0 °C has a pH of 5.35. The value of Ka for HA is
________.
A) 3.0 × 10-5
B) 1.8 × 10-5
C) 7.1 × 10-9
D) 1.3 × 10-10
E) 3.3 × 104
23) The Ka of hypochlorous acid (HClO) is 3.00 × 10-8. What is the pH at 25.0 °C of an aqueous solution
that is 0.0200 M in HClO?
A) +2.45
B) -2.45
C) -9.22
D) +9.22
E) +4.61
24) The Ka of acetic acid (HC2H3O2) is 1.8 × 10-5. What is the pH at 25.0 °C of an aqueous solution that is
0.100 M in acetic acid?
A) +2.87
B) -2.87
C) -11.13
D) +11.13
E) +6.61
25) The acid-dissociation constants of sulfurous acid (H2SO3) are Ka1 = 1.7 × 10-2 and Ka2 = 6.4 × 10-8 at
25.0 °C. Calculate the pH of a 0.163 M aqueous solution of sulfurous acid.
A) 4.53
B) 1.28
C) 1.86
D) 6.21
E) 1.93
26) The acid-dissociation constants of phosphoric acid (H3PO4) are Ka1 = 7.5 × 10-3, Ka2 = 6.2 × 10-8, and
Ka3 = 4.2 × 10-13 at 25.0 °C. What is the pH of a 2.5 M aqueous solution of phosphoric acid?
A) 1.82
B) 0.40
C) 2.51
D) 0.86
E) 0.13
27) The pH of a 0.55 M aqueous solution ammonia, NH3, at 25.0 °C is 11.50. What is the value of Kb for
NH3?
A) 2.0 × 10-9
B) 1.1 × 10-9
C) 6.0 × 10-5
D) 1.8 × 10-5
E) none of the above
28) A 0.15 M aqueous solution of the weak base B at 25.0 °C has a pH of 8.88. The value of Kb for B is
________.
A) 3.0 × 10-5
B) 1.8 × 10-5
C) 3.9 × 10-10
D) 1.3 × 10-10
E) none of the above
29) The pH of a 0.30 M solution of a weak acid is 2.67. What is the Ka for this acid?
A) 2.1 × 10-4
B) 4.4 × 10-4
C) 1.5 × 10-4
D) 6.6 × 10-4
E) none of the above
30) Z- is a weak base. An aqueous solution of NaZ is prepared by dissolving 0.350 mol of NaZ in
sufficient water to yield 1.0 L of solution. The pH of the solution was 8.93 at 25.0 °C. The Kb of Z- is
________.
A) 1.2 × 10-5
B) 6.9 × 10-9
C) 2.1 × 10-10
D) 9.9 × 10-2
E) 2.8 × 10-12
31) The pH of a 0.10 M solution of a weak base is 9.82. What is the Kb for this base?
A) 2.1 × 10-4
B) 4.4 × 10-8
C) 8.8 × 10-8
D) 6.6 × 10-4
E) 2.0 × 10-5
32) Determine the pH of a 0.35 M aqueous solution of CH3NH2 (methylamine). The Kb of methylamine is
4.4 × 10-4.
A) 10.00
B) 3.86
C) 12.09
D) 1.96
E) 13.24
33) An aqueous solution contains 0.050 M of methylamine. The concentration of hydroxide ion in this
solution is ________ M. Kb for methylamine is 4.4 × 10-4.
A) 0.050
B) 2.2 × 10-5
C) 2.9 × 10-3
D) 4.5 × 10-3
E) 4.7 × 10-3
34) An aqueous solution contains 0.050 M of methylamine. The concentration of H+ in this solution is
________ M. Kb for methylamine is 4.4 × 10-4.
A) 0.050
B) 2.2 × 10-13
C) 2.9 × 10-13
D) 4.5 × 10-13
E) 2.2 × 10-12
35) The acid-dissociation constant, Ka, for gallic acid is 4.57 × 10-3. What is the base-dissociation constant,
Kb, for the gallate ion?
A) 4.57 × 10-3
B) 2.19 × 10-12
C) 5.43 × 10-5
D) 7.81 × 10-6
E) 2.19 × 102
36) The base-dissociation constant, Kb, for pyridine, C5H5N, is 1.4 × 10-9. The acid-dissociation constant,
Ka, for the pyridinium ion, C5H5NH+, is ________.
A) 1.0 × 10-7
B) 1.4 × 10-23
C) 7.1 × 10-4
D) 1.4 × 10-5
E) 7.1 × 10-6
37) The Ka for HCN is 4.9 × 10-10. What is the value of Kb for CN-?
A) 2.0 × 10-5
B) 4.0 × 10-6
C) 4.9 × 104
D) 4.9 × 10-24
E) 2.0 × 109
38) Ka for HF is 7.0 × 10-4. Kb for the fluoride ion is ________.
A) 2.0 × 10-8
B) 1.4 × 10-11
C) 7.0 × 10-18
D) 7.0 × 10-4
E) 1.4 × 103
39) Ka for HCN is 4.9 × 10-10. What is the pH of a 0.068 M aqueous solution of sodium cyanide?
A) 0.74
B) 2.96
C) 11.07
D) 13.24
E) 7.00
40) Ka for HX is 7.5 × 10-12. What is the pH of a 0.15 M aqueous solution of NaX?
A) 7.97
B) 1.96
C) 6.00
D) 8.04
E) 12.10
41) The pH of a 0.15 M aqueous solution of NaZ (the sodium salt of HZ) is 10.7. What is the Ka for HZ?
A) 1.6 × 10-6
B) 6.0 × 10-9
C) 8.9 × 10-4
D) 1.3 × 10-12
E) 3.3 × 10-8
16.3 Algorithmic Questions
1) The conjugate base of NH3 is ________.
A) NH2-
B) NH4+
C) NH2OH
D) H3O+
E) OH-
2) The conjugate base of H2PO4- is ________.
A) H3PO4
B) HPO42-
C) PO43-
D) H3O+
E) OH-
3) In acidic solution, ________.
A) [H3O+] > [OH-]
B) [H3O+] = [OH-]
C) [H3O+] < [OH-]
D) [OH-] > 7.00
E) [H3O+] = 0M
30
4) Which solution below has the highest concentration of hydroxide ions?
A) pH = 12.5
B) pH = 11
C) pH = 8.3
D) pH = 6.0
E) pH = 3.0
5) Which solution below has the highest concentration of hydronium ions?
A) pH = 3.0
B) pH = 10
C) pH = 7.0
D) pH = 6.4
E) pH = 11.2
6) An aqueous solution at 25.0°C contains [H+] = 0.085 M. What is the pH of the solution?
A) 1.07
B) -1.07
C) 13.0
D) 0.0850
E) 1.20 ×
7) The pH of an aqueous solution at 25.0 °C is 10.55. What is the molarity of H+ in this solution?
A) 2.8 × 10-11
B) 3.5 × 10-4
C) 3.45
D) 1.1 × 10-13
E) 3.5 × 1010
8) Calculate the molarity of hydroxide ion in an aqueous solution that has a pOH of 3.00.
A) 1.0 × 10-3
B) 11.00
C) 1.0 × 10-11
D) 3.0 × 10-14
E) 1.1 × 10-13
9) What is the pH of an aqueous solution at 25.0 °C in which [H+] is 0.0015 M?
A) 6.50
B) 2.82
C) -2.82
D) -6.50
E) none of the above
10) What is the pOH of an aqueous solution at 25.0 °C in which [H+] is 0.0050 M?
A) 8.70
B) 11.70
C) -11.70
D) -8.70
E) none of the above
11) What is the pH of an aqueous solution at 25.0 °C in which [OH-] is 0.0030 M?
A) 5.81
B) -11.48
C) 2.52
D) -2.52
E) 11.48
