University of South Florida

CHM 2046

Chapter 18 Electrochemistry

1)Identify oxidation.

1. 1. Increase in oxidation number.
   2. Loss of electrons.
   3. Gain of electrons.
   4. Decrease in oxidation number.
   5. Both A and B

2. Which of the following statements is TRUE?
   1. 1. 1. A reduction process corresponds to an increase in oxidation state as a result of loss of electrons.
         2. An oxidation process involves the loss of electrons resulting in an increase in oxidation state.
         3. An oxidation process corresponds to a decrease in oxidation state as a result of a gain of electrons.
         4. During a reduction process electrons are lost, while during an oxidation they are gained.
         5. During a reduction process an oxidation state increases, while in an oxidation process an oxidation state decreases.

3.  What element is being oxidized in the following (unbalanced) redox reaction?

MnO4? (aq) + H2C2O4(aq) → Mn2+(aq) + CO2(g)

1. 1. 1. 6. C
         7. O
         8. Mn
         1. H

1. 1. Zn
   2. N
   3. H
   4. O

1. 1. H

1. 2. O
   3. Cl
   4. N
   5. C

6. What element is being oxidized in the following (unbalanced) redox reaction?

H2O2(l) + ClO2(aq) → ClO2?(aq) + O2(g)

1. 1. H
   2. O
   3. Cl
   4. N
   5. C

1. 1. Cr
   2. O
   3. H
   4. Cl

8. What element is being reduced in the following (unbalanced) redox reaction?

Cr(OH)4?(aq) + ClO?(aq) → CrO42-(aq) + Cl?(aq)

1. 1. Cr
   2. O
   3. H
   4. Cl

9. Balance the following redox reaction if it occurs in acidic solution. What are the coefficients in front of H2C2O4 and H2O in the balanced reaction?

A) H2C2O4 = 5, H2O = 8

B) H2C2O4 = 1, H2O = 1

C) H2C2O4 = 5, H2O = 1

D) H2C2O4 = 1, H2O = 4

E) H2C2O4 = 3, H2O = 2

10. Balance the following redox reaction if it occurs in acidic solution. What are the coefficients in front of H? and Fe3+ in the balanced reaction?

Fe2+(aq) + MnO4– (aq) → Fe3+(aq) + Mn2+(aq) A) H? = 2, Fe3+ = 3

B) H? = 8, Fe3+ = 5

C) H? = 3, Fe3+ = 2

D) H? = 5, Fe3+ = 1

E) H? = 8, Fe3+ = 1

11. Balance the following redox reaction if it occurs in acidic solution. What are the coefficients in front of Zn and H+ in the balanced reaction?

B) Zn = 1, H+ = 4

C) Zn = 4, H+ = 10

D) Zn = 2, H+ = 4

E) Zn = 3, H+ = 5

12. Balance the following redox reaction if it occurs in acidic solution. What are the coefficients in front of Cd and Ag+ in the balanced reaction?

Cd(s) + Ag+(aq) → Ag(s) + Cd2+(aq)

12. 1. Cd = 1, Ag+ = 2
    2. Cd = 1, Ag+ = 1
    3. Cd = 2, Ag+ = 1
    4. Cd = 2, Ag+ = 2
    5. Cd = 3, Ag+ = 1
13. Balance the following redox reaction if it occurs in basic solution. What are the coefficients in front of Br2 and OH? in the balanced reaction?

B) Br2 = 2, OH– = 5

C) Br2 = 3, OH– = 3

D) Br2 = 3, OH– = 6

E) Br2 = 1, OH– = 6

14. Balance the following redox reaction if it occurs in basic solution. What are the coefficients in front of ClO2 and H2O in the balanced reaction?

H2O2(l) + ClO2(aq) → ClO2– (aq) + O2(g)

1. 1. ClO2 = 1, H2O = 1
   2. ClO2 = 1, H2O = 2
   3. ClO2 = 4, H2O = 3
   4. ClO2 = 4, H2O = 2
   5. ClO2 = 2, H2O = 2

15. Balance the following redox reaction if it occurs in basic solution. What are the coefficients in front of Cr(OH)4? and ClO? in the balanced reaction?

16. Balance the following redox reaction if it occurs in basic solution. What are the coefficients in front of Al and F2 in the balanced reaction?

Al(s) + F2(g)→ Al3+(aq) + F– (aq)

A) Al = 2, F2 = 3

B) Al = 2, F2 = 6

C) Al = 1, F2 = 1

D) Al = 2, F2 = 1

E) Al = 3, F2 = 2

17. Identify the location of oxidation in an electrochemical cell.
    1. The anode.
    2. The cathode.
    3. The electrode.
    4. The salt bridge.
    5. The socket.

18. Identify the location of reduction in an electrochemical cell.
    1. the anode
    2. the cathode
    3. the electrode
    4. the salt bridge
    5. the socket

19. Define a salt bridge.

1. A pathway, composed of salt water, that ions pass through.
2. A pathway in which no ions flow.
3. A pathway between the cathode and anode in which ions are reduced.
4. A pathway between the cathode and anode in which ions are oxidized.
5. A pathway through which counterions can flow between the half-cells without the solutions in the half-cell totally mixing.

20. Determine the redox reaction represented by the following cell notation. Mg(s) ? Mg2+(aq) || Cu2+(aq) ? Cu(s)
    1. Cu(s) + Mg2+(aq) → Mg(s) + Cu2+(aq)
    2. Mg(s) + Cu2+(aq) → Cu(s) + Mg2+(aq)

C) 2 Mg(s) + Cu2+(aq) → Cu(s) + 2 Mg2+(aq)

D) 2 Cu(s) + Mg2+(aq) → Mg(s) + 2 Cu2+(aq)

E) 3 Mg(s) + 2 Cu2+(aq) → 2 Cu(s) + 3 Mg2+(aq)

21. Determine the cell notation for the redox reaction given below. Sn(s) + 2 Ag?(aq) → Sn2+(aq) + 2 Ag(s)

1. Ag+(aq) ? Ag(s) || Sn(s) ? Sn2+(aq)
2. Ag(s) ? Ag+(aq) || Sn2+(aq) ? Sn(s)
3. Sn(s) ? Sn2+(aq) || Ag+(aq) ? Ag(s)
4. Sn2+(aq) ? Sn(s) || Ag(s) ? Ag+(aq)
5. Sn(s) ? Ag(s) || Sn2+(aq) ? Ag+(aq)

22. Determine the cell notation for the redox reaction given below. Pb(s) + 2 H?(aq) → Pb2+(aq) + H2(g)

A) H+(aq) ? H2(g) ? Pt || Pb(s) ? Pb2+(aq)

B) H2(g) ? H+(aq) ? Pt || Pb2+(aq) ? Pb(s)

C) Pb2+(aq) ? Pb(s) || H2(g) ? H+(aq) ? Pt

D) Pb(s) ? Pb2+(aq) || H+(aq) ? H2(g) ? Pt

E) Pb(s) ? H2(g) || Pb2+(aq) ? H+(aq) ? Pt

23. Determine the cell notation for the redox reaction given below. 3 Cl2(g) + 2 Fe(s) → 6 Cl– (aq) + 2  Fe3+(aq)
    1. Cl2(g) ? Cl– (aq) ? Pt || Fe(s) ? Fe3+(aq)
    2. Cl– (aq) ? Cl2(g) ? Pt || Fe3+(aq) ? Fe(s)
    3. Fe3+(aq) ? Fe(s) || Cl– (aq) ? Cl2(g) ? Pt
    4. Fe(s) ? Cl2(g) || Fe3+(aq) ? Cl– (aq) ? Pt
    5. Fe(s) ? Fe3+(aq) || Cl2(g) ? Cl– (aq) ? Pt
24. What is the reduction half-reaction for the following overall galvanic cell reaction? Co2+(aq) + 2Ag(s) → Co(s) + 2 Ag+(aq)
    1. 1. 1. Ag(s) + e- → Ag+(aq)
          2. Ag+(aq) + e- → Ag(s)
          3. Co2+(aq) + 2 e- → Co(s)
          4. Co2+(aq) + e- → Co(s)
25. What is the shorthand notation that represents the following galvanic cell reaction? Pb(s) + Cu(NO3)2(aq) → Pb(NO3)2(aq) + Cu(s)
    1. 1. 1. Pb(s) ? Pb2+(aq) ?? Cu2+(aq) ? Cu(s)

25. 1. 1. 2. Cu(s) ? Cu2+(aq) ?? Pb2+(aq) ? Pb(s)
          3. Pb(s) ? NO3-(aq) ?? NO3-(aq) ? Cu(s)
          4. Cu(s) ? Cu(NO3)2(aq) ?? Pb(NO3)2(aq) ? Pb(s)
26. What is the shorthand notation that represents the following galvanic cell reaction? 2Fe2+(aq) + F2(g) → 2Fe3+(aq) + 2F-(aq)

A) Fe2+(aq) ? Fe3+(aq) ?? F2(g) ? F-(aq)

B) Fe(s) ? Fe2+(aq) ?? Fe3+(aq) F2(g) ? F-(aq) ? C(s)

C) Pt(s) ? Fe3+(aq), Fe2+(aq), F2(g) ?? F-(aq) ? C(s)

D) Pt(s) ? Fe2+(aq), Fe3+(aq) ?? F2(g) ? F-(aq) ? C(s)

27. For the galvanic cell reaction, expressed below using shorthand notation, what half-reaction occurs at the cathode?

Zn(s) ? Zn2+(aq) ?? Ni2+(aq) ? Ni(s)

27. 1. 1. 1. Zn(s) → Zn2+(aq) + 2 e-
          2. Zn2+(aq) + 2 e- → Zn(s)
          3. Ni(s) → Ni2+(aq) + 2 e-
          4. Ni2+(aq) + 2 e- → Ni(s)
28. What is the balanced chemical equation for the galvanic cell reaction expressed using shorthand notation below?

Al(s) ? Al3+(aq) ?? Fe2+(aq) ? Fe(s)

A) 2Al(s) + 3Fe2+(aq) → 2Al3+(aq) + 3Fe(s)

B) 3Al(s) + 2Fe2+(aq) → 3Al3+(aq) + 2Fe(s)

C) 2Fe(s) + 3Al3+(aq) → 2Fe2+(aq) + 3Al(s)

D) 3Fe(s) + 2Al3+(aq) → 3Fe2+(aq) + 2Al(s)

29. What is the balanced equation for the galvanic cell reaction expressed using shorthand notation below?

Ni(s) ? Ni2+(aq) ?? Cl2(g) ? Cl-(aq) ? C(s)

29. 1. 1. 1. Ni(s) + 2Cl-(aq) → Ni2+(aq) + Cl2(g)
          2. Ni(s) + Cl2(g) → Ni2+(aq) + 2Cl-(aq)
          3. Ni2+(aq) + 2Cl-(aq) → Ni(s) + Cl2(g)
          4. Ni2+(aq) + 2Cl-(aq) → NiCl2(s)
30. What is the reducing agent in the redox reaction represented by the following cell notation? Ni(s) ? Ni2+(aq) || Ag+(aq) ? Ag(s)
    1. Ni(s)

30. 2. Ni2+(aq)
    3. Ag+(aq)
    4. Ag(s)
    5. Pt
31. What is the oxidizing agent in the redox reaction represented by the following cell notation? Ni(s) ? Ni2+(aq) Ag+(aq) ? Ag(s)
    1. Ni(s)
    2. Ni2+(aq)
    3. Ag+(aq)
    4. Ag(s)
    5. Pt(s)
32. What is the oxidizing agent in the redox reaction represented by the following cell notation? Sn(s) ? Sn2+(aq) || Ag+(aq) ? Ag(s)
    1. Sn(s)
    2. Ag+(aq)
    3. Sn2+(aq)
    4. Ag(s)
    5. Pt
33. What is the reducing agent in the redox reaction represented by the following cell notation? Sn(s) ? Sn2+(aq)

    

     Ag+(aq) ? Ag(s)
    1. Sn(s)
    2. Ag+(aq)
    3. Sn2+(aq)
    4. Ag(s)
    5. Pt(s)

34. What is undergoing reduction in the redox reaction represented by the following cell notation?

Fe(s) ? Fe3+(aq) || Cl2(g) ? Cl– (aq) ? Pt

1. 1. Fe(s)
   2. Fe3+(aq)
   3. Cl2(g)
   4. Cl– (aq)
   5. Pt

35. What is undergoing oxidation in the redox reaction represented by the following cell notation?

1. 1. Fe(s)

1. 2. Fe3+(aq)
   3. Cl2(g)
   4. Cl?(aq)
   5. Pt(s)

36. What is undergoing oxidation in the redox reaction represented by the following cell notation?

Pb(s) ? Pb2+(aq) || H+(aq) ? H2(g) ? Pt

1. 1. H2(g)
   2. H+(aq)
   3. Pb2+(aq)
   4. Pb(s)
   5. Pt

37. What is undergoing reduction in the redox reaction represented by the following cell notation?

1. 1. H2(g)
   2. H+(aq)
   3. Pb2+(aq)
   4. Pb(s)
   5. Pt(s)

38. What statement is NOT true about standard electrode potentials?
    1. E°cell is positive for spontaneous reactions.
    2. Electrons will flow from more negative electrode to more positive electrode.
    3. The electrode potential of the standard hydrogen electrode is exactly zero.
    4. E°cell is the difference in voltage between the anode and the cathode.
    5. The electrode in any half-cell with a greater tendency to undergo reduction is positively charged relative to the standard hydrogen electrode and therefore has a positive E°.

39. Which of the following is TRUE about standard electrode potentials?
    1. E°cell is negative for spontaneous reactions.
    2. Electrons will flow from a more positive electrode to a more negative electrode.
    3. The electrode potential of the standard hydrogen electrode is exactly zero.
    4. E°cell is the sum in voltage between the anode and the cathode.
    5. The electrode in any half-cell with a greater tendency to undergo reduction is negatively charged relative to the standard hydrogen electrode and therefore has E° < 0.

40. Which of the following is the strongest reducing agent?
    1. Sn2+(aq)
    2. Cr3+(aq)
    3. Sn4+(aq)
    4. Cr(s)
    5. Sn(s)

41. Which of the following is the strongest reducing agent?
    1. Na(s)
    2. Li+(aq)
    3. Ca(s)
    4. Ca2+(aq)
    5. Li(s)

42. Which of the following is the strongest reducing agent?
    1. Al(s)
    2. Zn(s)
    3. Mg(s)
    4. Al3+(aq)
    5. Mg2+(aq)
43. Which of the following is the weakest reducing agent?
    1. Al(s)
    2. Zn(s)
    3. Mg(s)
    4. Al3+(aq)
    5. Mg2+(aq)
44. Which of the following is the weakest reducing agent?
    1. Br2(l)
    2. Au3+(aq)
    3. Ag(s)
    4. Br– (aq)
    5. Au(s)

45. Which of the following is the strongest oxidizing agent?
    1. MnO2(s)
    2. Cl– (aq)
    3. Cu+ (aq)
    4. SO42– (aq)
    5.  

46. Which of the following is the strongest oxidizing agent?
    1. Br2(l)
    2. Au3+(aq)
    3. Ag(s)
    4. Br– (aq)
    5. Au(s)

47. Which of the following is the strongest oxidizing agent?
    1. H2O2(aq)
    2. Fe3+(aq)
    3. ClO2(g)
    4. I2(s)
    5. Fe(s)

48. Which of the following is the weakest oxidizing agent?
    1. Sn2+(aq)

1. 2. Cr3+(aq)
   3. Sn4+(aq)
   4. Cr(s)
   5. Sn(s)

49. Which of the following is the weakest oxidizing agent?
    1. H2O2(aq)
    2. Fe3+(aq)
    3. ClO2(g)
    4. I2(s)
    5. Fe(s)

50. The electrolysis of an aqueous sodium chloride solution using inert electrodes produces gaseous chlorine at one electrode. At the other electrode gaseous hydrogen is produced, and the solution becomes basic around the electrode. Which of the following is the equation for the cathode half-reaction in this electrolytic cell?

a. 2Cl- ? Cl2 + 2e-

b. 2H2O + 2e- ? H2 + 2OH-

c. Cl2 + 2e- ? 2Cl-

d. H2 + 2OH- ? 2H2O + 2e-

e. none of these

51. An aqueous copper(II) sulfate solution is electrolyzed for 45 minutes. A 3.2 ampere current is used. What mass of copper is produced?

a. 0.95 g

2. 1.9 g
3. 2.8 g
4. 4.6 g
5. 5.5 g

52. Which of the following shorthand galvanic cell notations for the zinc - copper standard cell is correct? Cu2+ + Zn ? Zn2+ + Cu

1. Cu2+ | Cu || Zn | Zn2+
2. Cu2+ | Cu || Cu | Cu2+

c. Cu2+ | 2e- || 2e- | Zn

d. Zn | Zn2+ || Cu2+ | Cu

e. Zn | Cu2+ || Zn2+ | Cu

53. A voltaic cell is constructed by immersing a strip of copper metal in 1.0 M CuSO4 solution and a strip of aluminum in 0.50 M Al2(SO4)3 solution. A wire and a salt bridge complete the circuit. The aluminum strip loses mass, and the concentration of aluminum ions in the solution increases. The copper electrode gains mass, and the concentration of copper ions decreases. What is the cell potential?

a. +1.28 V

b. +2.00 V

c. +2.34 V

d. +2.50 V

e. +3.66 V

54. Calculate the cell potential for the following voltaic cell. Cr|Cr3+(1.0 × 10-2 M)||Co2+(1.0

× 10-5 M)|Co

a. +0.35 V

b. +0.91 V

c. +0.57 V

d. +0.28 V