Chemistry 213
Spring 2015
Exam III - B
Name_______________________________________
MULTIPLE CHOICE (1 Point Each). Choose the one alternative that best completes the statement or answers the
question.
1) Which one of the following is the weakest acid?
A) HNO 2 (Ka = 4.5 × 10-4)
B) Acetic acid (Ka = 1.8 × 10-5)
C) HClO (Ka = 3.0 × 10 -8)
D) HF (Ka = 6.8 × 10-4)
E) HCN (Ka = 4.9 × 10 -10)
1)
2) Of the following acids, ________ is not a strong acid.
A) HCl
B) H2SO4
C) HClO4
2)
D) HNO 2
E) HNO 3
3) A solution containing which one of the following pairs of substances will be a buffer solution?
A) RbCl, HCl
B) NaI, HI
C) KBr, HBr
D) CsF, HF
E) none of the above
1
3)
4) What is the pH of an aqueous solution at 25.0 °C that contains 3.98 × 10 -9 M hydroxide ion?
A) 8.40
B) 5.60
C) 9.00
D) 7.00
E) 3.98
4)
5) What is the conjugate acid of NH3?
A) NH4+
B) NH3
5)
C) NH3+
2
D) NH4OH
E) NH2+
6) The Ka for HCN is 4.9 × 10 -10. What is the value of Kb for CN-?
6)
A) 2.0 × 10 9
B) 4.0 × 10-6
C) 4.9 × 10 -24
D) 2.0 × 10 -5
E) 4.9 × 104
7) Which of the following aqueous solutions has the highest [OH-]?
A) a 1 × 10 -4 M solution of HNO3
B) a 1 × 10-3 M solution of NH4Cl
C) a solution with a pH of 3.0
D) a solution with a pOH of 12.0
E) pure water
3
7)
8) The solubility of manganese (II) hydroxide (Mn(OH)2) is 2.2 × 10 -5 M. What is the Ksp of
8)
Mn(OH)2?
A) 2.1 × 10-14
B) 1.1 × 10 -14
C) 4.8 × 10-10
D) 2.2 × 10-5
E) 4.3 × 10-14
9) Of the following solutions, which has the greatest buffering capacity?
A) 0.821 M HC2H3O2 and 0.713 M NaC2H3O2
B) 0.121 M HC2H3O2 and 0.116 M NaC2H3O2
C) 0.521 M HC2H3O2 and 0.217 M NaC2H3O2
D) 0.365M HC2H3O2 and 0.497 M NaC2H3O2
4
9)
10) 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?
10)
A) 1.1 × 10-9
B) 6.0 × 10-5
C) 3.6 × 10-4
D) 2.0 × 10-9
E) none of the above
11) A 0.1 M solution of ________ has a pH of 7.0.
A) Na2S
B) KF
C) NaNO 3
11)
D) NH4Cl
E) NaF
Consider the following table of K sp values.
Name
Formula
Ksp
Cadmium carbonate
CdCO3
Cadmium hydroxide
Cd(OH)2
5.2 × 10-12
2.5 × 10-14
Calcium fluoride
Silver iodide
Zinc carbonate
AgI
3.9 × 10-11
8.3 × 10-17
ZnCO3
1.4 × 10-11
CaF 2
12) Which compound listed below has the greatest molar solubility in water?
A) AgI
B) Cd(OH)2
C) CaF 2
D) CdCO3
5
12)
E) ZnCO 3
SHORT ANSWER (4 Points Each). Write the word or phrase that best completes each statement or answers the
question.
13) The Ka of benzoic acid is 6.30 × 10 -5. The pH of a buffer prepared by combining 70.0 mL
13)
of 1.00 M potassium benzoate and 30.0 mL of 1.00 M benzoic acid is ________.
14) The concentration of iodide ions in a saturated solution of lead (II) iodide is ________ M.
The solubility product constant of PbI2 is 1.4 × 10 -8.
6
14)
15) The Ka of hypochlorous acid (HClO) is 3.0 × 10-8 at 25.0 °C. What is the percent
15)
ionization of hypochlorous acid in a 0.015 M aqueous solution of HClO at 25.0 °C?
16) 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?
7
16)
Answer Key
Testname: 213E3S15B
1) E
2) D
3) D
4) B
5) A
6) D
7) E
8) E
9) A
10) C
11) C
12) C
13) 4.57
14) 3.0 × 10 -3
15) 0.14
16) 1.8 × 10-5
8