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Acid-Base Equilibria
Copyright D. Herrick |
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20 Questions from past exams.
Practice for speed. Aim
for 2 minutes per problem.
(all concentrations in Molarity units) |
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| 1. |
Which
statement is FALSE? |
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| A) |
An
acid which has Ka = 3 ×10-8 is
called a weak acid. |
| B) |
The
concentration of hydroxide ion in pure liquid water is
1.00 × 10-7 M. |
| C) |
The
degree of ionization of a strong acid in a 0.10 M
solution is nearly 100%. |
| D) |
Pure
liquid water has [H+] = 1.00 × 10-7 M. |
| E) |
An
equilibrium reaction having Kc >> 1
normally favors formation of products. |
| F) |
A
Brønsted-Lowry acid is a proton donor. |
| G) |
A
Brønsted-Lowry acid and its conjugate base have equal
concentrations. |
|
| 2. |
What's the pH of a solution in which [H+] is 2.75
× 10-4 M? |
|
| A)
2.75 |
B)
3.01 |
C)
3.56 |
D)
4.28 |
E)
5.03 |
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| 3. |
Which
is the weakest acid? |
|
| A) |
HC7H5O2
, Ka = 6.3 × 10-5 |
| B) |
H3BO3
, Ka = 5.9 × 10-10 |
| C) |
HNO2
, Ka = 4.5 × 10-4 |
| D) |
HClO
, Ka = 3.5 × 10-8 |
| E) |
H2CO3
, Ka = 4.3 × 10-7 |
| F) |
HC3H3O3
, Ka = 1.4 × 10-4 |
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| 4. |
If
HCN has Ka = 5.0 × 10-10, then Kb
for CN- is: |
|
| A) |
5.0
× 10-10 |
F) |
2.2
× 10-12 |
| B) |
2.2
× 10-5 |
G) |
5.0
× 10-3 |
| C) |
9.3 |
H) |
2.0
× 10-5 |
| D) |
5.0
× 10-4 |
I) |
4.7
× 10-4 |
| E) |
4.7 |
J) |
5.0
× 10 |
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| 5. |
Which
is the strongest base? |
|
| A) |
HS-
, Kb = 1.0 × 10-7 |
| B) |
NH2OH
, Kb = 1.1 × 10-8 |
| C) |
CO32-
, Kb = 2.1 × 10-4 |
| D) |
CH3NH2
, Kb = 4.4 × 10-4 |
| E) |
C6H5NH2
, Kb = 4.2 × 10-10 |
| F) |
NH2CONH2
, Kb = 1.5 × 10-14 |
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| 6. |
If
an acid HA has pKa = 5.43, its conjugate base
has pKb = |
|
| A)
8.57 |
B)
9.43 |
C)
-5.43 |
D)
10.86 |
E)
7.61 |
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| 7. |
Benzoic
acid, HC7H5O2, has Ka
= 6.46 ×10
-5. Sodium
benzoate, NaC7H5O2, is
used as a food preservative because of its antimicrobial
action. The ratio [HC7H5O2]/[C7H5O2-] in a food with a pH of 3.00 is: |
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| A)
6.45 |
B)
15.5 |
C)
4.19 |
D)
11.9 |
E)
0.67 |
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| 8. |
Nitrous acid HNO2 has Ka = 4.40×10 -4.
The pH of a 0.85 M solution of HNO2 is:
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| A)
2.36 |
B)
4.20 |
C)
3.69 |
D)
1.71 |
E)
0.82 |
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| 9. |
The pH of a 0.15 M solution of hydrochloric acid (HCl) is:
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| A)
2.36 |
B)
4.20 |
C)
3.69 |
D)
1.71 |
E)
0.82 |
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| 10. |
[OH-] in a 0.10 M solution of NH3
(Kb
= 1.80 ×10 -5) is: |
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| A) |
4.24 × 10-3 |
F) |
1.80 × 10-6 |
| B) |
1.34 × 10-3 |
G) |
4.24 × 10-2 |
| C) |
0.10 |
H) |
0.30 |
| D) |
1.80 × 10-5 |
I) |
1.34 × 10-2 |
| E) |
0.20 |
J) |
1.00 × 10-7 |
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| 11. |
The
pH of 0.25 M NH3 (Kb
= 1.80 × 10-5) is: |
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| A)
11.33 |
B)
7.864 |
C)
9.25 |
D)
2.69 |
E)
10.41 |
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| 12. |
What
is the pH of 0.75 M hypochlorous acid (HClO
, pKa = 7.46)? |
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| A)
5.60 |
B)
4.87 |
C)
6.54 |
D)
8.12 |
E)
3.79 |
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| 13. |
Nitrous acid HNO2 has Ka = 4.40 × 10 -4.
Determine the pH of a 0.20 M solution of NaNO2 (a completely
soluble salt).
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|
| A)
6.39 |
B)
8.33 |
C)
7.07 |
D)
9.42 |
E)
7.95 |
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| 14. |
Nitrous acid HNO2 has Ka = 4.40 × 10 -4. The pH of an
acid-salt aqueous solution prepared as 0.15 M HNO2 and 0.20 M
NaNO2 is:
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| A)
0.44 |
B)
3.48 |
C)
4.73 |
D)
6.29 |
E)
7.95 |
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| 15. |
What is [OH-] in a solution that has equal concentrations of
NH3 (Kb = 1.8 × 10-5) and NH4Cl? |
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| A) |
4.24 × 10-3 |
F) |
0.20 |
| B) |
1.34 × 10-3 |
G) |
1.80 × 10-6 |
| C) |
0.30 |
H) |
1.00 |
| D) |
0.10 |
I) |
4.24 × 10-2 |
| E) |
1.80 × 10-5 |
J) |
1.34 × 10-2 |
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| 16. |
0.01 mol of
an acid HA is diluted with water to 2.0 liter of solution.
Determine the equilibrium concentration of hydronium ion according to
HA(aq) + H2O(l) 
H3O+ (aq) + A-(aq),
which has Ka
= 1.00 × 10-1.
This involves
the full quadratic equation. -- Erlene
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|
| A) |
4.77 × 10-3 |
E) |
1.31 × 10-5
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| B) |
2.63 × 10-4 |
F) |
7.07 × 10-2
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| C) |
5.81 × 10-3 |
G) |
2.63 × 10-5 |
| D) |
2.24 × 10-3 |
H) |
0.00 |
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| 17. |
The pH of a 0.125 M solution of NaOH is:
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| A)
0.94 |
B)
12.83 |
C)
13.10 |
D)
11.47 |
E)
8.21 |
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| 18. |
The pH of a 0.125 M solution of NaCl is:
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| A)
0.00 |
B)
6.06 |
C)
14.00 |
D)
7.00 |
E)
7.94 |
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| 19. |
The
Brønsted acids in the reversible reaction
HCOO-(aq)
+ H2O(l)
HCOOH(aq) + OH-(aq)
are: |
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| A) |
HCOO-
and HCOOH |
| B) |
HCOO-
and OH- |
| C) |
H2O
and OH- |
| D) |
H2O
and HCOOH |
| E) |
H2O,
HCOOH, and OH- |
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| 20. |
Which
one is not a conjugate acid/base pair? |
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| A) |
H3O+
/ OH- |
| B) |
HBr
/ Br - |
| C) |
HCO3-
/ CO32- |
| D) |
HONH3+
/ HONH2 |
| E) |
H2S
/ HS- |
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