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. Slide 1 of 33

What is the oxidation state of Cr in ? 1. +8 2. +7 3. +6 4. -1 5. -2 potassium dichromate Slide 2 of 33

What is the oxidation state of Cr in ? 1. +8 2. +7 3. +6 Catch ball and stick figure p. 1049 (right side) 4. -1 5. -2 potassium dichromate Slide 3 of 33

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. Slide 4 of 33

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. Slide 5 of 33

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 6 of 33

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

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 = -0.23 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 Slide 8 of 33

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 = -0.23 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 Slide 9 of 33

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 -1.10 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

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 -1.10 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 11 of 33

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: 1. 1.103 3. -0.423 2. 0.423 4. -1.103 Slide 12 of 33

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: 1. 1.103 3. -0.423 2. 0.423 4. -1.103 Slide 13 of 33

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? 1. 2.023 2. 1.563 3. 0.643 4. -0.643 5. -1.563 Slide 14 of 33

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? 1. 2.023 2. 1.563 3. 0.643 4. -0.643 5. -1.563 Slide 15 of 33

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. Slide 16 of 33

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. Slide 17 of 33

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. Slide 18 of 33

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. Slide 19 of 33

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 = 1. 23 V 2H+(aq) + 2e- ⇌H2(g) Eo = 0.00 V Fe2+ (aq) + 2e- ⇌ Fe(s) Eo = -0.44 V 2H2O(l) +2e- ⇌ H2(g) + OH-(aq) Eo = -0.83 V 1. True 2. False Slide 20 of 33

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 = 1. 24 V 2H+(aq) + 2e- ⇌H2(g) Eo = 0.00 V Fe2+ (aq) + 2e- ⇌ Fe(s) Eo = -0.44 V 2H2O(l) +2e- ⇌ H2(g) + OH-(aq) Eo = -0.83 V 1. True 2. False Slide 21 of 33

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) Slide 22 of 33

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) Slide 23 of 33

In the electrochemical cell to the right the concentrations of Mn2+ and Cr3+ are 0.010 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 1. -0.48 V 2. -0.45 V 2. -0.44 V Cr(NO3)3 Mn(NO3)2 4. -0.43 V 5. -0.40 V Slide 24 of 33

In the electrochemical cell to the right the concentrations of Mn2+ and Cr3+ are 0.010 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 1. -0.48 V 2. -0.45 V 2. -0.44 V Cr(NO3)3 Mn(NO3)2 4. -0.43 V 5. -0.40 V Slide 25 of 33

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 Slide 26 of 33

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

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

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

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 30 of 33

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

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]2- + 24 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 Slide 32 of 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]2- + 24 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 Slide 33 of 33