Chemistry -Test Electrochemistry

Chemistry 12 Unit 5 Electrochemistry

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Unit 5 PreTest 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. MoO4

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Electrochemistry Pre-Test.docx 2

6. What is the oxidation number of carbon in the ethanoate ion C2H3O2

? A. +1 B. + 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 SO4

2 8. Which of the following skeletal half-reactions are reductions?

I Mn(OH)2 MnO2

II H2O H2

III H2O2 OH

A. I and II only B. II and III only C. I, II and III only D. 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? A. Fe3+ is too strong a reducing agent. B. Fe3+ forms an acidic solution. C. I is oxidized in the solution. D. FeI3 is soluble.



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?

Observed Colour Product Formed

A. becomes colourless O2 B. remains purple H2 C. remains purple O2 D. becomes colourless 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 104 mol B. 1.4 x 104 mol C. 5.2 x 102 mol D. 1.3 x 103 mol



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 + O2 16. Which of the following is correct as the cell operates? Direction of K+ Ion Migration Mass of the Cathode

A. toward the Zn increases B. toward the Pt remains the same C. toward the Zn remains the same D. toward the Pt 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



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? Anode Mass Cathode Mass

A. increases no change B. decreases increases C. decreases no change D. increases 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




22. What is the cathode reaction for this cell?

A. H2O O2 + 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? K+ Ion Electron Movement Movement

A. towards the Pt towards the Pt B. towards the Cu towards the Pt C. towards the Cu towards the Cu D. towards the Pt towards the Cu

24. What is the standard cell voltage?

A. +0.62V B. 0.75V C. +1.43V D. +0.75V




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



Use the following halfreactions to answer questions 28 and 29.

1 2H2SO3 + 2H+ + 4e S2O3

2 + 3H2O

2 SnCl62 + 2e Sn2+ + 6Cl

3 Hg22+ + e Hg(l)

4 Sb2O5 + 6H+ + 4e 2Sb(OH)2

+ + H2O

28. A redox reaction occurs when Sb2O5 is mixed with S2O3

2 , but does not when Sb2O5 is mixed with Hg. A solution of SnCl6

2 has no effect on S2O32 . Which of the following describes the order of the half-

reaction 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




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



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 half-

reactions 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 halfcell reaction for the electrolysis of molten KBr ?

A. K+ + e K

B. K K+ + e

C. H2O 2e + 2H+ + O2

D. 2Br Br2 + 2e



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

A. Cu2+ 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



Answers to Multiple Choice 1. A 2. C 3. B 4. C 5. D 6. C 7. D 8. B 9. C 10. A

11. C 12. A 13. A 14. D 15. D 16. D 17. C 18. B 19. B 20. C

21. D 22. C 23. A 24. D 25. B 26. B 27. B 28. A 29. C 30. D

31. A 32. D 33. C 34. D 35. D 36. A 37. D 38. B 39. B 40. C

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