Chemistry 12
Unit 5 Electrochemistry
Unit 5 Pre−Test Electrochemistry
PART A: Multiple Choice Questions
For each of the following, choose the alternative that BEST answers the question or completes the statement.
1. Consider the following skeletal redox reaction in acidic solution:
Mn3+  Mn2+ + MnO2
Which of the following is the balanced oxidation half-reaction?
A. 2H2O + Mn3+  MnO2 + 4H+ + e–
B. O2 + Mn3+  MnO2 + 3e–
C. e– + Mn3+  Mn2+
D. Mn3+  Mn2+ + e–
2. Consider the following balanced redox equation in acidic solution:
5H2O + 2CoCl2 + OCl–  2Co(OH)3 + 5Cl– + 4H+
Which of the following describes the amounts and locations of OH– and H2O if the equation is
balanced in basic solution?
A. 1 H2O on the left and 4OH– on the right
B. 5 H2O on the left and 4OH– on the left
C. 1 H2O on the left and 4OH– on the left
D. 1 H2O on the left and no OH–.
3. An oxidizing agent
A. is oxidized.
B. is reduced.
C. causes another reactant to be reduced.
D. loses electrons.
4. Consider the following equation:
Co + SO42– + 4H+  Co2+ + H2SO3 + H2O
Which statement is correct?
A. The hydrogen is reduced and the oxygen is oxidized.
B. The hydrogen is reduced and the cobalt is oxidized.
C. The cobalt is oxidized and the sulphur is reduced.
D. The sulphur is oxidized and the cobalt is reduced.
5. Which of the following contains molybdenum with its highest oxidation number?
A. Mo6Cl12
B. MoCl5
C. Mo2S3
D. MoO42–
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Chemistry 12
Unit 5 Electrochemistry
6. What is the oxidation number of carbon in the ethanoate ion C2H3O2– ?
A. +1
B. +½
C. 0
D. –1
7. Which of the following changes involve sulphur atoms losing electrons?
A. H2SO4  H2S2O7
B. SO2  S
C. S2Cl2  S22–
D. S2O32–  SO42–
8. Which of the following skeletal half-reactions are reductions?
A.
B.
C.
D.
I
Mn(OH)2  MnO2
II
H2O  H2
III
H2O2  OH−
I and II only
II and III only
I, II and III only
I only
9. Which of the following is the strongest oxidizing agent?
A. Ag+
B. Cl–
C. Br2
D. Na
10. What is the result of adding Pb(s) to CuSO4(aq)?
A. A reaction occurs but the electrical conductivity of the solution remains the same.
B. No reaction occurs.
C. The electrical conductivity of the solution increases.
D. The electrical conductivity of the solution decreases.
11. If Fe3+(aq) and Cl–(aq) are mixed, FeCl3(aq) results. However, if Fe3+(aq) and I–(aq) are mixed,
FeI3(aq) does not result.
Which of the following best describes why?
3+
A. Fe is too strong a reducing agent.
B. Fe3+ forms an acidic solution.
C. I– is oxidized in the solution.
D. FeI3 is soluble.
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Chemistry 12
Unit 5 Electrochemistry
12. A redox titration is carried out by adding purple KMnO4 solution from a burette to a solution of H2O2
in a flask, under acidic conditions. Which of the following would correctly describe the observed
colour and the product formed in the flask before the equivalence point is reached?
A.
B.
C.
D.
Observed Colour
becomes colourless
remains purple
remains purple
becomes colourless
Product Formed
O2
H2
O2
H2
13. Consider the following redox reaction:
2I2 + S2O32– + 3H2O  4I– + 2H2SO3 + 2H+
A 10.0 mL sample of an I2 solution is titrated with 13.2 mL of 0.0374 M Na2S2O3. What is the [I2 ] of
the sample?
A. 0.
0987 M
B. 0.
0494 M
C. 0.
0426 M
D. 0.
0247 M
14. The titration of a 25.0 mL SnCl2 sample, in acidic solution, requires 14.4 mL of 0.030 M K2Cr2O7. The
balanced equation for the reaction is shown below:
Cr2O72– + 14H+ + 3Sn2+  3Sn4+ + 2Cr3+ + 7H2O
What is the number of moles of SnCl2 in the original sample?
A. 4.3 x 10–4 mol
B. 1.4 x 10–4 mol
C. 5.2 x 10–2 mol
D. 1.3 x 10–3 mol
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Chemistry 12
Unit 5 Electrochemistry
Use the following electrochemical cell diagram to answer questions 15 to 17.
15. What is the overall cell reaction?
A. Zn2+ + 2H2O  Zn + H2O2 + 2H+
B. Zn + H2O2 + 2H+  Zn2+ + 2H2O
C. Zn + H2O2 + 2H+ + 4e–  Zn2+ + 2H2O
D. Zn2+ + H2O2  Zn + H2O + ½O2
16. Which of the following is correct as the cell operates?
A.
B.
C.
D.
Direction of K+ Ion Migration
toward the Zn
toward the Pt
toward the Zn
toward the Pt
Mass of the Cathode
increases
remains the same
remains the same
increases
17. What is the cell voltage at equilibrium?
A. +2.54V
B. –2.54V
C. 0.00V
D. +1.02V
18. Consider the following reaction:
Ni2+ + 2Ag  2Ag+ + Ni
Which of the following is true?
E°
Reaction
A.
+1.06 V
spontaneous
B.
–1.06 V
non-spontaneous
C.
–0.54 V
non-spontaneous
D.
+0.54 V
spontaneous
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Chemistry 12
Unit 5 Electrochemistry
Use the following diagram to answer questions 19 to 21.
19. Which of the following represents the anode half-cell reaction?
A. Ag+ + e–  Ag
B. Ag  Ag+ + e–
C. 2Cl–  Cl2 + 2e–
D. Cl2 + 2e–  2Cl–
20. What changes in mass occur to the anode and cathode?
A.
B.
C.
D.
Anode Mass
increases
decreases
decreases
increases
Cathode Mass
no change
increases
no change
decreases
21. What is the voltage for this cell under standard conditions?
A. +2.16 V
B. –0.24 V
C. –0.56 V
D. +0.56 V
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Chemistry 12
Unit 5 Electrochemistry
Use the following diagram to answer questions 22 to 24.
22. What is the cathode reaction for this cell?
A. H2O  ½O2 + 2H+ + 2e–
B. Na+ + e–  Na
C. Br2 + 2e–  2Br–
D. 2Br–  Br2 + 2e–
23. Which of the following best describes the movement of potassium ions and electrons as the cell
operates?
A.
B.
C.
D.
K+ Ion
Movement
towards the Pt
towards the Cu
towards the Cu
towards the Pt
Electron
Movement
towards the Pt
towards the Pt
towards the Cu
towards the Cu
24. What is the standard cell voltage?
A. +0.62V
B. –0.75V
C. +1.43V
D. +0.75V
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Chemistry 12
Unit 5 Electrochemistry
Use the following diagram to answer questions 25 to 27.
25. What is the half-cell reaction at the anode?
A. Pd  Pd2+ + 2e–
B. Ni  Ni2+ + 2e–
C. Pd2+ + 2e–  Pd
D. Ni2+ + 2e–  Ni
26. What best describes the flow of electrons?
A. from Pd to Ni
B. from Ni to Pd
C. into the solution around the Ni electrode
D. from cathode to anode
27. What is the voltage for the oxidation half-reaction of Pd?
A. +1.
14 V
B. –0.
62 V
C. +0.
62 V
D. +0.
88 V
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Chemistry 12
Unit 5 Electrochemistry
Use the following half–reactions to answer questions 28 and 29.
1
2H2SO3 + 2H+ + 4e−  S2O32− + 3H2O
2
SnCl62− + 2e−  Sn2+ + 6Cl−
3
½ Hg22+ + e−  Hg(l)
4
Sb2O5 + 6H+ + 4e−  2Sb(OH)2+ + H2O
28. A redox reaction occurs when Sb2O5 is mixed with S2O32– , but does not when Sb2O5 is mixed with Hg.
A solution of SnCl62– has no effect on S2O32– . Which of the following describes the order of the halfreaction reduction potentials from highest to lowest?
A. 3 > 4 > 1 > 2
B. 2 > 1 > 4 > 3
C. 2 > 4 > 1 > 3
D. 3 > 1 > 4 > 2
29. The initial voltage of a standard electrochemical cell based on the half-reactions 3 and 4 above, is
0.22V. If Hg22+ is reduced, what is the reduction potential for half-reaction 4?
A. +1.02V
B. +0.63V
C. +0.58V
D. –0.58V
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Chemistry 12
Unit 5 Electrochemistry
Use the following diagram to answer questions 30 to 32.
30. In the above cell, which of the following best describes the movement of the electrons through the
wire?
A. They move from right to left towards the anode.
B. They move from left to right towards the anode.
C. They move from left to right towards the cathode.
D. They move from right to left towards the cathode.
31. Which of the following best describes what happens to the mass of the anode and the mass of the
cathode as the cell operates?
Anode Mass
Cathode Mass
A.
stays constant
stays constant
B.
stays constant
decreases
C.
decreases
stays constant
D.
decreases
increases
32. What is the standard voltage (E°) for the cell?
A. +1.68 V
B. +0.43 V
C. +0.77 V
D. +1.34 V
33. Which of the following would prevent the corrosion of an iron nail?
A. Store the nail wrapped in cobalt wire in a beaker of distilled water.
B. Store the nail in a beaker of distilled water.
C. Store the nail in dry air.
D. Store the nail in Cl2(g).
34. Which of the following occurs when a piece of iron is cathodically protected with Mg?
A. Fe2+ + 2e–  Fe
B. Fe  Fe2+ + 2e–
C. Mg2+ + 2e–  Mg
D. Mg  Mg2+ + 2e–
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Chemistry 12
Unit 5 Electrochemistry
35. This diagram represents an electrolytic cell:
Which of the following correctly describes the labelled parts X and Y of the cell?
X
Y
A.
anode
voltmeter
B.
anode
power supply
C.
cathode
voltmeter
D.
cathode
power supply
36. Consider the electrolysis of molten MgCl2 using copper electrodes. Which of the following halfreactions will occur at the cathode?
A. Mg2+ + 2e–  Mg
B. Cl2 + 2e–  2Cl–
C. Mg  Mg2+ + 2e–
D. Cu2+ + 2e–  Cu
37. Which of the following is the anode half–cell reaction for the electrolysis of molten KBr ?
A. K+ + e–  K
B. K  K+ + e–
C. H2O  2e– + 2H+ + ½O2
D. 2Br–  Br2 + 2e–
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Chemistry 12
Unit 5 Electrochemistry
Use the following diagram to answer questions 38 and 40.
38. What products would form at the anode and cathode as this cell operates?
Anode
Cathode
2+
A.
Cu
Ni
B.
I2
Ni
C.
Ni
I2
D.
O2
H2
39. In the above cell, if 1.0 M NiI2 is replaced with molten NiI2 , what products would form at the
electrodes?
Anode
Cathode
A.
Ni
I2
B.
I2
Ni
C.
Cu2+
Ni
D.
O2
H2
40. Consider the following diagram:
Why would this cell fail to electroplate the Fe nail with copper?
A. The porous barrier prevents reaction.
B. The Fe nail is the cathode.
C. The Fe nail is the anode.
D. The Pt is inert.
END OF EXAMINATION
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Chemistry 12
Unit 5 Electrochemistry
Answers to Multiple Choice
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
A
C
B
C
D
C
D
B
C
A
Electrochemistry Pre-Test.docx
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
C
A
A
D
D
D
C
B
B
C
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
D
C
A
D
B
B
B
A
C
D
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
A
D
C
D
D
A
D
B
B
C
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