Which of the following is a conjugate acid/base pair?
A.
HCl/OCl–
B.
H2SO4/SO42–
C.
NH4+/NH3
D.
H3O+/OH–
E.
none of these
2.
For the stepwise dissociation of aqueous H3PO4, which of the following is not a conjugate acid-base pair?
A.
HPO42– and PO43–
B.
H3PO4 and H2PO4–
C.
H2PO4– and HPO42–
D.
H2PO4– and PO43–
E.
H3O+ and H2O
3.
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
4.
Calculate the [H+] in a solution that has a pH of 11.70.
A.
2.3 M
B.
11.7 M
C.
5.0 ´ 10–3 M
D.
2.0 ´ 10–12 M
E.
none of these
5.
Calculate the pH of 0.250 M HNO3(aq).
A.
0.600
B.
2.50
C.
12.0
D.
1.20
E.
13.4
6.
Which of the following indicates the most acidic solution?
A.
[OH–] = 0.5 M
B.
[H+] = 0.3 M
C.
pOH = 5.9
D.
pH = 1.2
E.
[H+] = 1 ´ 10–4 M
7.
For nitrous acid, HNO2, Ka = 4.0 ´ 10–4. Calculate the pH of 0.25 M HNO2.
A.
2.00
B.
2.30
C.
2.70
D.
3.70
E.
none of these
8.
Determine the molarity of a solution of the weak acid HClO2 (Ka = 1.10 ´ 10–2) if it has a pH of 1.25.
A.
0.287 M
B.
1.23 M
C.
0.819 M
D.
3.17 M
E.
1.52 M
9.
In a solution prepared by dissolving 0.100 mole of propionic acid in enough water to make 1.00 L of solution, the pH is observed to be 1.35. The Ka for propionic acid (HC3H5O2) is:
A.
2.0 ´ 10–2
B.
3.6 ´ 10–2
C.
4.5 ´ 10–2
D.
5.0 ´ 10–12
E.
none of these
10.
The pain killer morphine is a weak base when added to water. The reaction produces one mole of hydroxide ions for every one mole of morphine that dissolves. The Kb is 1.60 ´ 10–6. What is the pH of a 5.00 ´ 10–3 M solution of morphine?
A.
8.23
B.
9.95
C.
11.3
D.
10.2
E.
none of these
11.
Calculate the percentage of pyridine (C5H5N) that forms pyridinium ion, C5H5NH+, in a 0.10 M aqueous solution of pyridine (Kb = 1.7 ´ 10–9):
A.
0.0060%
B.
1.6%
C.
0.77%
D.
0.060%
E.
0.013%
12.
A 0.10-mol sample of a diprotic acid, H2A, is dissolved in 250 mL of water. The Ka1 of this acid is 1.0 ´ 10–5 and Ka2 is 1.0 ´ 10–10. Calculate the concentration of A2– in this solution.
A.
1.0 ´ 10–5 M
B.
2.0 ´ 10–3 M
C.
4.0 ´ 10–6 M
D.
1.0 ´ 10–10 M
E.
0.40 M
13.
What combination of substances will give a buffered solution that has a pH of 5.05? (Assume each pair of substances is dissolved in 5.0 L of water.) (Kb for NH3 = 1.8 ´ 10–5; Kb for C5H5N = 1.7 ´ 10–9)
A.
1.0 mole NH3 and 1.5 mole NH4Cl
B.
1.5 mole NH3 and 1.0 mole NH4Cl
C.
1.0 mole C5H5N and 1.5 mole C5H5NHCl
D.
1.5 mole C5H5N and 1.0 mole C5H5NHCl
E.
none of these
14.
You have solutions of 0.200 M HNO2 and 0.200 M KNO2 (Ka for HNO2 = 4.00 ´ 10–4). A buffer of pH 3.000 is needed. What volumes of HNO2 and KNO2 are required to make 1 liter of buffered solution?
A.
500 mL of each
B.
286 mL HNO2; 714 mL KNO2
C.
413 mL HNO2; 587 mL KNO2
D.
714 mL HNO2; 286 mL KNO2
E.
587 mL HNO2; 413 mL KNO2
15.
A solution contains 0.250 M HA (Ka = 1.0 × 10–6) and 0.45 M NaA. What is the pH after 0.10 mole of HCl is added to 1.00 L of this solution?
A.
3.17
B.
3.23
C.
6.00
D.
10.77
E.
10.83
16.
A weak acid, HF, is in solution with dissolved sodium fluoride, NaF. If HCl is added, which ion will react with the extra hydrogen ions from the HCl to keep the pH from changing?
A.
OH–
B.
Na+
C.
F–
D.
Na–
E.
none of these
17.
Which of the following is true for a buffered solution?
A.
The solution resists change in its [H+].
B.
The solution will not change its pH very much even if a concentrated acid is added.
C.
The solution will not change its pH very much even if a strong base is added.
D.
Any H+ ions will react with a conjugate base of a weak acid already in solution.
E.
all of these
18.
The following questions refer to the following system: A 1.0-liter solution contains 0.25 M HF and 0.60 M NaF (Ka for HF is 7.2 ´ 10–4)
What is the pH of this solution?
A.
1.4
B.
3.5
C.
4.6
D.
2.8
E.
0.94
19.
The following questions refer to the following system: A 1.0-liter solution contains 0.25 M HF and 0.60 M NaF (Ka for HF is 7.2 ´ 10–4)
If one adds 0.30 liters of 0.020 M KOH to the solution what will be the change in pH?
A.
0.0
B.
0.2
C.
0.4
D.
0.5
E.
none of these
20.
Calculate the [H+] in a solution that is 0.10 M in NaF and 0.20 in HF. (Ka = 7.2 ´ 10–4)
A.
0.20 M
B.
7.0 ´ 10–4 M
C.
1.4 ´ 10–3 M
D.
3.5 ´ 10–4 M
E.
none of these
21.
Which of the following will not produce a buffered solution?
A.
100 mL of 0.1 M Na2CO3 and 50 mL of 0.1 M HCl
B.
100 mL of 0.1 M NaHCO3 and 25 mL of 0.2 M HCl
C.
100 mL of 0.1 M Na2CO3 and 75 mL of 0.2 M HCl
D.
50 mL of 0.2 M Na2CO3 and 5 mL of 1.0 M HCl
E.
100 mL of 0.1 M Na2CO3 and 50 mL of 0.1 M NaOH
22.
How many moles of HCl need to be added to 150.0 mL of 0.50M NaZ to have a solution with a pH of 6.50? (Ka of HZ is 2.3 × 10–5). Assume negligible volume of the HCl.
A.
6.8 × 10–3
B.
7.5 × 10–2
C.
5.0 × 10–1
D.
1.0 × 10–3
E.
none of these
23.
Calculate the pH of a solution that is 0.2 M in acetic acid (Ka = 1.8 ´ 10–5) and 0.2 M in sodium acetate.
A.
4.7
B.
9.3
C.
7.0
D.
5.4
E.
8.6
24.
Consider a solution consisting of the following two buffer systems: At pH 6.4, which one of the following is true of the relative amounts of acid and conjugate base present?
A.
[H2CO3] > [HCO3–] and [H2PO4–] > [HPO42–]
B.
[H2CO3] = [HCO3–] and [H2PO4–] > [HPO42–]
C.
[H2CO3] = [HCO3–] and [HPO42–] > [H2PO4–]
D.
[HCO3–] > [H2CO3] and [HPO42–] > [H2PO4–]
E.
[H2CO3] > [HCO3–] and [HPO42–] > [H2PO4–]
25.
For a solution equimolar in HCN and NaCN, which statement is false?
A.
This is an example of the common ion effect.
B.
The [H+] is larger than it would be if only the HCN was in solution.
C.
The [H+] is equal to the Ka.
D.
Addition of more NaCN will shift the acid dissociation equilibrium of HCN to the left.
E.
Addition of NaOH will increase [CN–] and decrease [HCN].
26.
Consider a solution of 2.0 M HCN and 1.0 M NaCN (Ka for HCN = 6.2 × 10–10). Which of the following statements is true?
A.
The solution is not a buffer because [HCN] is not equal to [CN–].
B.
The pH will be below 7.00 because the concentration of the acid is greater than that of the base.
C.
[OH–] > [H+]
D.
The buffer will be more resistant to pH changes from addition of strong acid than of strong base.
E.
All of these are false.
27.
A 10-mL sample of tartaric acid is titrated to a phenolphthalein endpoint with 20. mL of 1.0 M NaOH. Assuming tartaric acid is diprotic, what is the molarity of the acid?
A.
2.0
B.
1.0
C.
4.0
D.
10.
E.
impossible to determine
28.
If 25 mL of 0.75 M HCl are added to 100 mL of 0.25 NaOH, what is the final pH?
A.
12.70
B.
12.80
C.
1.30
D.
1.20
E.
7.00
29.
A 50.00-mL sample of 0.100 M KOH is titrated with 0.100 M HNO3. Calculate the pH of the solution after the 52.00 mL of HNO3 is added.
A.
6.50
B.
3.01
C.
2.71
D.
2.41
E.
none of these
30.
Consider the titration of 100.0 mL of 0.500 M NH3 (Kb = 1.8 ´ 10–5) with 0.500 M HCl.
At the stoichiometric point of this titration, the [H+] is:
A.
1.0 ´ 10–7 M
B.
1.8 ´ 10–5 M
C.
1.2 ´ 10–5 M
D.
5.6 ´ 10–10 M
E.
none of these
31.
A 75.0-mL sample of 0.0500 M HCN (Ka = 6.2 ´ 10–10) is titrated with 0.500 M NaOH. What is the [H+] in the solution after 3.0 mL of 0.50 M NaOH have been added?
A.
1.0 ´ 10–7 M
B.
4.1 ´ 10–10 M
C.
5.2 ´ 10–13 M
D.
9.3 ´ 10–10 M
E.
none of these
32.
A student titrates an unknown weak acid, HA, to a pale pink phenolphthalein endpoint with 25.0 mL of 0.100 M NaOH. The student then adds 13.0 mL of 0.100 M HCl. The pH of the resulting solution is 4.7. Which of the following is true?
A.
At pH 4.7, half the conjugate base, A–, has been converted to HA.
B.
The pKa of the acid is 4.7.
C.
The pKa of the acid is less than 4.7.
D.
The pKa of the acid is greater than 4.7.
E.
More than one of these is correct.
33.
Consider the following information about the diprotic acid ascorbic acid (H2As for short) (molar mass = 176.1). The titration curve for disodium ascorbate, Na2As, with standard HCl is shown below:
What major species is (are) present at point III?
A.
As2– and HAs–
B.
HAs– only
C.
HAs– and H2As
D.
H2As only
E.
H2As and H+
34.
Consider the following information about the diprotic acid ascorbic acid (H2As for short) (molar mass = 176.1). The titration curve for disodium ascorbate, Na2As, with standard HCl is shown below:
