Summer 2003
CHEMISTRY 115
EXAM 3(A)
1. In which of the following solutions would you expect AgCl to have the lowest
solubility?
A. 0.02 M BaCl2
B. pure water
C. 0.02 M NaCl
D. 0.02 M KCl
2. Calculate the pH of a 1-L solution containing 0.40 mol HF and 0.1 mol HCl. (Ka =
6.8x10-4 for HF)
A. 0.40
B. 1.0
C. 2.6
D. 0.016
3. What is the effect of addition of an acid to a buffered solution of HF and KF?
A. [HF] will increase, [F-] will decrease
B. [HF] will increase, [F-] will increase
C. [HF] will decrease, [F-] will decrease
D. [HF] will decrease, [F-] will increase
4. Calculate pH of a buffer composed of 0.085 M HNO2 (Ka=4.5x10-4)and 0.1 M KNO2
A. 8.4
B. 7.0
C. 5.6
D. 3.4
5. Which of the following substances, when added to a solution of hydrofluoric acid,
could be used to prepare a buffer solution?
A. NaF
B. NaNO3
C. NaCl
D. NaBr
6. Consider the titration diagram shown on the plot below. What type of substance was
originally in the flask?
A. weak acid
B. weak base
C. strong acid
D. strong base
7. 20 mL of 0.1 M HF (Ka=6.8x10-4) is titrated with 0.1 M NaOH. What is the pH of the
solution when 10 mL of NaOH have been added?
A. 7.2
B. 6.3
C. 3.2
D. 2.1
8. What is the molar solubility of MgC2O4 (Ksp=8.6x10-5)? [H2C2O4 is the oxalic acid.]
A. 9.3 x 10-3
B. 6.4 x 10-13
C. 7.1 x 10-9
D. 2.8 x 10-2
9. Which of the following substances will increase in solubility if the pH of the saturated
solution of the compound is lowered?
A. AgCl
B. AgI
C. Cr(OH)3
D. PbCl2
10. Which substance is serving as a reducing agent in the following reaction?
Fe2S3 + 12HNO3 → 2Fe(NO3)3 + 3S + 6NO2 + 6H2O
A. HNO3
B. S
C. NO2
D. Fe2S3
11. What is the oxidation number of manganese in KMnO4?
A. 0
B. +1
C. +7
D. +5
12. What is the coefficient of iodine when the following reaction (acidic solution) is
correctly balanced?
MnO4- + I- → Mn2+ + I2
A. 5
B. 7
C. 2
D. 4
13. Which of the following transformation could take place at the cathode of an
electrochemical cell?
A. MnO2 → MnO4B. Br2 → BrO3C. Mn2+ → MnO4D. HSO4- → H2SO3
14. The standard reduction potentials for Pb2+ and Ag+ are –0.13 V and +0.8 V,
respectively. Calculate E0 for a cell in which the overall reaction is
Pb + 2Ag+ → Pb2+ + 2Ag
A. 1.06
B. 1.47
C. 0.67
D. 0.93
15. Respective standard reduction potentials of Pb2+ and Ni2+ are –0.13 V and -0.28 V.
An electrochemical cell is built from Pb electrode in Pb2+ solution and Ni electrode in
Ni2+ solution. The reduction reaction will occur on the electrode which is called:
A. Pb, anode
B. Pb, cathode
C. Ni, anode
D. Ni, cathode
16. Calculate ∆G (in J) for the reaction of elemental bromine Br2 (E0red = 1.09 V) with
chloride ion (Cl2, Eored = 1.36)
A. 2.1 x 104
B. 5.21 x 104
C. –2.62 x 105
D. 2.10 x 105
17. The standard emf for Zn/Cu voltaic cell is 1.10 V. Calculate the cell emf when the
concentration of Zn2+ and Cu2+ in the solution are 0.01 M and 1.0 M, respectively.
A. 0.98 V
B. 1.04 V
C. 1.16 V
D. 1.32 V
18. Using the table of standard reduction potentials indicate the metal which could
provide cathode protection to zinc:
A. Fe
B. Ag
C. Al
D. Cu
19. The electrolysis of NiCl2 produces Ni and Cl2. What is the minimum external emf
needed to drive electrolysis under standard conditions?
A. 1.36 V
B. 1.64 V
C. 0.28 V
D. 1.08 V
20. Identify the products of electrolysis of an aqueous solution of CuI2 and FeCl2 (acidic
solution). [Hint: Assume that the concentration of OH- is equal to zero.]
A. Cu and O2
B. Fe and Cl2
C. Fe and O2
D. Cu and I2
EXAM 3(B)
1. In which of the following solutions would you expect AgCl to have the lowest
solubility?
A. pure water
B. 0.02 M BaCl2
C. 0.02 M KCl
D. 0.02 M NaCl
2. Calculate the pH of a 1-L solution containing 0.40 mol HF and 0.1 mol HCl. (Ka =
6.8x10-4 for HF)
A. 0.016
B. 0.40
C. 2.6
D. 1.0
3. What is the effect of addition of an acid to a buffered solution of HF and KF?
A. [HF] will decrease, [F-] will increase
B. [HF] will increase, [F-] will increase
C. [HF] will decrease, [F-] will decrease
D. [HF] will increase, [F-] will decrease
4. Calculate pH of a buffer composed of 0.085 M HNO2 (Ka=4.5x10-4)and 0.1 M KNO2
A. 5.6
B. 7.0
C. 8.4
D. 3.4
5. Which of the following substances, when added to a solution of hydrofluoric acid,
could be used to prepare a buffer solution?
A. NaCl
B. NaNO3
C. NaF
D. NaBr
6. Consider the titration diagram shown on the plot below. What type of substance was
originally in the flask?
A. weak acid
B. strong acid
C. weak base
D. strong base
7. 20 mL of 0.1 M HF (Ka=6.8x10-4) is titrated with 0.1 M NaOH. What is the pH of the
solution when 10 mL of NaOH have been added?
A. 3.2
B. 6.3
C. 7.2
D. 2.1
8. What is the molar solubility of MgC2O4 (Ksp=8.6x10-5)? [H2C2O4 is the oxalic acid.]
A. 6.4 x 10-13
B. 9.3 x 10-3
C. 2.8 x 10-2
D. 7.1 x 10-9
9. Which of the following substances will increase in solubility if the pH of the saturated
solution of the compound is lowered?
A. PbCl2
B. AgCl
C. Cr(OH)3
D. AgI
10. Which substance is serving as a reducing agent in the following reaction?
Fe2S3 + 12HNO3 → 2Fe(NO3)3 + 3S + 6NO2 + 6H2O
A. HNO3
B. Fe2S3
C. NO2
D. S
11. What is the oxidation number of manganese in KMnO4?
A. +7
B. 0
C. +5
D. +1
12. What is the coefficient of iodine when the following reaction (acidic solution) is
correctly balanced?
MnO4- + I- → Mn2+ + I2
A. 7
B. 5
C. 4
D. 2
13. Which of the following transformation could take place at the cathode of an
electrochemical cell?
A. Mn2+ → MnO4B. MnO2 → MnO4C. Br2 → BrO3D. HSO4- → H2SO3
14. The standard reduction potentials for Pb2+ and Ag+ are –0.13 V and +0.8 V,
respectively. Calculate E0 for a cell in which the overall reaction is
Pb + 2Ag+ → Pb2+ + 2Ag
A. 1.06
B. 0.93
C. 1.47
D. 0.67
15. Respective standard reduction potentials of Pb2+ and Ni2+ are –0.13 V and -0.28 V.
An electrochemical cell is built from Pb electrode in Pb2+ solution and Ni electrode in
Ni2+ solution. The reduction reaction will occur on the electrode which is called:
A. Ni, cathode
B. Ni, anode
C. Pb, cathode
D. Pb, anode
16. Calculate ∆G (in J) for the reaction of elemental bromine Br2 (E0red = 1.09 V) with
chloride ion (Cl2, Eored = 1.36)
A. –2.62 x 105
B. 2.10 x 105
C. 2.1 x 104
D. 5.21 x 104
17. The standard emf for Zn/Cu voltaic cell is 1.10 V. Calculate the cell emf when the
concentration of Zn2+ and Cu2+ in the solution are 0.01 M and 1.0 M, respectively.
A. 1.16 V
B. 0.98 V
C. 1.04 V
D. 1.32 V
18. Using the table of standard reduction potentials indicate the metal which could
provide cathode protection to zinc:
A. Cu
B. Fe
C. Al
D. Ag
19. The electrolysis of NiCl2 produces Ni and Cl2. What is the minimum external emf
needed to drive electrolysis under standard conditions?
A. 1.64 V
B. 1.36 V
C. 1.08 V
D. 0.28 V
20. Identify the products of electrolysis of an aqueous solution of CuI2 and FeCl2 (acidic
solution). [Hint: Assume that the concentration of OH- is equal to zero.]
A. Fe and O2
B. Fe and Cl2
C. Cu and I2
D. Cu and O2