1. Principles & Modern Applications
General Chemistry
Principles & Modern Applications
10th Edition
Petrucci/Herring/Madura/Bissonnette
Chapter 20
Electrochemistry
Dr. Wendy Pell
University of Ottawa
Copyright © 2011 Pearson Canada Inc.
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2. What is the oxidation state of Cr in ?
1. +8
2. +7
3. +6
4. -1
5. -2
potassium dichromate
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3. What is the oxidation state of Cr in ?
1. +8
2. +7
3. +6
Catch ball and stick figure p (right side)
4. -1
5. -2
potassium dichromate
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4. 1. DG for the reaction is negative (the reaction is exergonic).
When a piece of copper metal is put into a solution of silver nitrate (AgNO3), silver metal is produced along with Cu2+, the latter of which is responsible for the blue color of the solution. Which of the following statements is false?
1. DG for the reaction is negative (the reaction is exergonic).
2. For every mole of Cu reacted, two moles of Ag is produced.
3. Cu is oxidized.
4. Ag is an oxidizing agent.
5. A solution of CuSO4 will be blue.
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5. 1. DG for the reaction is negative (the reaction is exergonic).
When a piece of copper metal is put into a solution of silver nitrate (AgNO3), silver metal is produced along with Cu2+, the latter of which is responsible for the blue color of the solution. Which of the following statements is false?
1. DG for the reaction is negative (the reaction is exergonic).
2. For every mole of Cu reacted, two moles of Ag is produced.
3. Cu is oxidized.
4. Ag is an oxidizing agent.
5. A solution of CuSO4 will be blue.
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6. For the electrochemical cell depicted to the right, which of the following is correct the shorthand notation?
Pb(s)
Pb(s), PbI2(s)
1.8 x 10-4 M
Pb(NO3)2
0.25 M KI
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7. For the electrochemical cell depicted to the right, which of the following is correct the shorthand notation?
Pb(s)
Pb(s), PbI2(s)
1.8 x 10-4 M
Pb(NO3)2
0.25 M KI
Slide 7 of 33

8. Given the following standard electrode potentials,
Ag+(aq) + e- ⇌ Ag(s) Eo = 0.80 V
Fe2+(aq) + 2e- ⇌ Fe(s) Eo = -0.44V
N2(g) + 5H+(aq) + 4e- ⇌ N2H5+(aq) Eo = V
Which of the following is spontaneous?
1. N2(g) + 2Fe(s) + 5 H+(aq) ⇌N2H5+(aq) + 2Fe2+(aq)
2. N2(g) + 4Ag(s) + 5 H+(aq) ⇌N2H5+(aq) + 4Ag+(aq)
3. Fe2+(aq) + 4Ag(s) ⇌+ 4Ag+ +Fe(s)
4. None of the above are spontaneous
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9. Given the following standard electrode potentials,
Ag+(aq) + e- ⇌ Ag(s) Eo = 0.80 V
Fe2+(aq) + 2e- ⇌ Fe(s) Eo = -0.44V
N2(g) + 5H+(aq) + 4e- ⇌ N2H5+(aq) Eo = V
Which of the following is spontaneous?
1. N2(g) + 2Fe(s) + 5 H+(aq) ⇌N2H5+(aq) + 2Fe2+(aq)
Catch photo p. 874, left side, bottom.
2. N2(g) + 4Ag(s) + 5 H+(aq) ⇌N2H5+(aq) + 4Ag+(aq)
3. Fe2+(aq) + 4Ag(s) ⇌+ 4Ag+ +Fe(s)
4. None of the above are spontaneous
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10. Zn2+ (aq) + Cu(s) ⇌ Cu2+(aq) + Zn(s)
A voltaic cell was produced based on the following overall reaction.
Zn2+ (aq) + Cu(s) ⇌ Cu2+(aq) + Zn(s)
The emf was measured to be 0.21 V. Eocell is V. Which of the following three statements is false?
1. When [Zn2+] and [Cu2+] = 1.00 M DG > 0
2. [Cu2+] must be far greater than [Zn2+]
3. DG < 0 for this cell but DGo > 0.
Slide 10 of 33

11. Zn2+ (aq) + Cu(s) ⇌ Cu2+(aq) + Zn(s)
A voltaic cell was produced based on the following overall reaction.
Zn2+ (aq) + Cu(s) ⇌ Cu2+(aq) + Zn(s)
The emf was measured to be 0.21 V. Eocell is V. Which of the following three statements is false?
1. When [Zn2+] and [Cu2+] = 1.00 M DG > 0
2. [Cu2+] must be far greater than [Zn2+]
3. DG < 0 for this cell but DGo > 0.
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12. has a cell potential of:
Given the two electrochemical cells to the right, a cell constructed according to the following shorthand notation
has a cell potential of:
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13. has a cell potential of:
Given the two electrochemical cells to the right, a cell constructed according to the following shorthand notation
has a cell potential of:
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14. Given the electrochemical cells to the right, what would be the cell potential for the electrochemical cell constructed as indicated by the following shorthand notation?
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15. Given the electrochemical cells to the right, what would be the cell potential for the electrochemical cell constructed as indicated by the following shorthand notation?
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16. 1. Decreasing [Ag+] in the cathode.
Which of the following would result in an increase in the cell potential?
1. Decreasing [Ag+] in the cathode.
2. Decreasing [Fe2+] in the anode.
3. Decreasing [Fe3+] in the anode.
4. Adding NaCl to the cathode.
5. Increasing [KNO3] in the salt bridge.
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17. 1. Decreasing [Ag+] in the cathode.
Which of the following would result in an increase in the cell potential?
1. Decreasing [Ag+] in the cathode.
2. Decreasing [Fe2+] in the anode.
3. Decreasing [Fe3+] in the anode.
4. Adding NaCl to the cathode.
5. Increasing [KNO3] in the salt bridge.
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18. Which of the following is false for the electrolysis of water? A B
Water is oxidized to form oxygen at
the anode.
2. Water is reduced to form hydrogen at the cathode.
3. The electrode marked A is the cathode and that marked B is the anode.
4. The hydrolysis of water is non-spontaneous and requires the input of energy from an external source.
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19. Which of the following is false for the electrolysis of water? A B
Water is oxidized to form oxygen at
the anode.
2. Water is reduced to form hydrogen at the cathode.
3. The electrode marked A is the cathode and that marked B is the anode.
4. The hydrolysis of water is non-spontaneous and requires the input of energy from an external source.
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20. O2(g) + 4H+(aq) +4e- ⇌ H2O(l) Eo = 1. 23 V
When pure iron is put into pure water, it produces H2 gas, and when pure iron is put into an acidic solution it produces H2 gas. Using the data below, state whether the above statement is true or false.
O2(g) + 4H+(aq) +4e- ⇌ H2O(l) Eo = V
2H+(aq) + 2e- ⇌H2(g) Eo = 0.00 V
Fe2+ (aq) + 2e- ⇌ Fe(s) Eo = V
2H2O(l) +2e- ⇌ H2(g) + OH-(aq) Eo = V
1. True
2. False
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21. O2(g) + 4H+(aq) +4e- ⇌ H2O(l) Eo = 1. 24 V
When pure iron is put into pure water, it produces H2 gas, and when pure iron is put into an acidic solution it produces H2 gas. Using the data below, state whether the above statement is true or false.
O2(g) + 4H+(aq) +4e- ⇌ H2O(l) Eo = V
2H+(aq) + 2e- ⇌H2(g) Eo = 0.00 V
Fe2+ (aq) + 2e- ⇌ Fe(s) Eo = V
2H2O(l) +2e- ⇌ H2(g) + OH-(aq) Eo = V
1. True
2. False
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22. The Nernst equation for the electrochemical cell depicted to the right is:
Ecell
KNO3 Pb Al
Pb(NO3)2 (0.1M)
Al(NO3)3 (0.5M)
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23. The Nernst equation for the electrochemical cell depicted to the right is:
Ecell
KNO3 Pb Al
Pb(NO3)2 (0.1M)
Al(NO3)3 (0.5M)
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24. In the electrochemical cell to the right the concentrations of Mn2+ and Cr3+ are M and 0.10 M, respectively. What is the cell potential? Use the equation to the right and do not use a calculator. Do use a pen and paper!
KNO3 Cr Mn V V V
Cr(NO3)3
Mn(NO3)2 V V
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25. In the electrochemical cell to the right the concentrations of Mn2+ and Cr3+ are M and 0.10 M, respectively. What is the cell potential? Use the equation to the right and do not use a calculator. Do use a pen and paper!
KNO3 Cr Mn V V V
Cr(NO3)3
Mn(NO3)2 V V
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26. Given that Ag+(aq) + e ⇌ Ag (s) Eo = 0.80 V What is Eocell ?
Consider an electrochemical cell that includes a silver metal anode in a 0.01 M AgNO3 aqueous electrolyte and a silver metal cathode in 0.1 M AgNO3.
Given that Ag+(aq) + e ⇌ Ag (s) Eo = 0.80 V
What is Eocell ?
Solution A Solution B
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27. Given that Ag+(aq) + e ⇌ Ag (s) Eo = 0.80 V What is Eocell ?
Consider an electrochemical cell that includes a silver metal anode in a 0.01 M AgNO3 aqueous electrolyte and a silver metal cathode in 0.1 M AgNO3.
Given that Ag+(aq) + e ⇌ Ag (s) Eo = 0.80 V
What is Eocell ?
Solution A Solution B
0 it is a concentration cell !
Slide 27 of 33

28. Given that Ag+(aq) + e ⇌ Ag (s) Eo = 0.80 V What is Eocell ?
Consider an electrochemical cell that includes a silver metal anode in a 0.01 M AgNO3 aqueous electrolyte and a silver metal cathode in 0.1 M AgNO3.
Given that Ag+(aq) + e ⇌ Ag (s) Eo = 0.80 V
What is Eocell ?
+0.80
-0.80
More information is required
Solution A Solution B
Slide 28 of 33

29. Given that Ag+(aq) + e ⇌ Ag (s) Eo = 0.80 V What is Eocell ?
Consider an electrochemical cell that includes a silver metal anode in a 0.01 M AgNO3 aqueous electrolyte and a silver metal cathode in 0.1 M AgNO3.
Given that Ag+(aq) + e ⇌ Ag (s) Eo = 0.80 V
What is Eocell ?
+0.80
-0.80
More information is required
Solution A Solution B
Slide 29 of 33

30. Which of the following would be produced in the largest abundance by mass by the consumption of 1 kW hour of electricity?
1. Ni from a solution of Ni3+ 11 12 10
2. Cu from a solution of Cu+
3. Zn from a solution of Zn2+
4. Ag from a solution of Ag+
5. Cd from a solution of Cd2+
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31. Which of the following would be produced in the largest abundance by mass by the consumption of 1 kW hour of electricity?
1. Ni from a solution of Ni3+ 11 12 10
2. Cu from a solution of Cu+
3. Zn from a solution of Zn2+
4. Ag from a solution of Ag+
5. Cd from a solution of Cd2+
Slide 31 of 33

32. Consider the following half-cell reactions involving platinum metal
Cl2 + 2e ⇌ 2Cl- Eo =1.358 V
O2 + 4H+ +4e ⇌ 2H2O Eo =1.23
Pt2+ + 2e ⇌ Pt Eo=1.18
NO3- +4H3O+ + 3e ⇌ NO + 6H2O Eo =0.957
NO3- +2H3O+ + 2e ⇌ NO2_ + 3H2O Eo =0.835
[PtCl4]2- + 2e ⇌ Pt + 4 Cl- Eo =0.755
[PtCl6]2- + 2e ⇌ [PtCl4] Cl- Eo =0.68
H+ + e ⇌ ½ H2(g) Eo = 0
2H2O + 2e ⇌ H2(g) + 2OH- Eo = -0.83
O2 + e ⇌ O2- Eo =-0.56
Platinum metal will oxidize in
Aqueous hydrochloric acid, HCl
Aqueous nitric acid, HNO3
In both aqueous hydrochloric acid and nitric acid
Only in a mixture of HNO3 and HCl
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33. Consider the following half-cell reactions involving platinum metal
Cl2 + 2e ⇌ 2Cl- Eo =1.358 V
O2 + 4H+ +4e ⇌ 2H2O Eo =1.23
Pt2+ + 2e ⇌ Pt Eo=1.18
NO3- +4H3O+ + 3e ⇌ NO + 6H2O Eo =0.957
NO3- +2H3O+ + 2e ⇌ NO2_ + 3H2O Eo =0.835
[PtCl4]2- + 2e ⇌ Pt + 4 Cl- Eo =0.755
[PtCl6]2- + 2e ⇌ [PtCl4] Cl- Eo =0.68
H+ + e ⇌ ½ H2(g) Eo = 0
2H2O + 2e ⇌ H2(g) + 2OH- Eo = -0.83
O2 + e ⇌ O2- Eo =-0.56
Platinum metal will oxidize in
Aqueous hydrochloric acid, HCl
Aqueous nitric acid, HNO3
In both aqueous hydrochloric acid and nitric acid
Only in a mixture of HNO3 and HCl
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