1. Lecture /28/07

2. Secondary Batteries (rechargeable) NiCad
E° = V
Cathode: 2NiO(OH) (s) + 2H2O + 2e-  2Ni(OH)2 (s) + 2OH-
Anode: Cd(s) + 2OH- -  Cd(OH)2 (s) + 2e-

3. Secondary Batteries (rechargeable) NiMH
E° = 1.4 V
Cathode: NiO(OH) (s) + H2O + e-  Ni(OH)2 (s) + OH-
Anode: MH(s) + OH- -  M (s) + H2O + e-

4. H2 (g) + 2 AgCl (s)  2H+ (aq) + 2 Cl- (aq) + 2Ag(s)
This reaction occurs in a cell with H2 (g) pressure of 1.0 atm and [Cl-] = 1.0 M at 25˚C; the measured Ecell = 0.34 V. What is the pH of the solution?
E˚(cathode) = 0.222V

5. Sn(s) + Pb2+ (aq)  Sn2+ (aq) + Pb(s)
Ecell = 0.01V for a galvanic cell with this reaction at 25˚C.
Sn(s) + Pb2+ (aq)  Sn2+ (aq) + Pb(s)
What is the equilibrium constant for the reaction?

6. Electrolysis of molten salts
Cathode: 2Na+ (l) + 2e-  2Na(l) E° = V
Anode: 2Cl- (l)  Cl2 (g) + 2e- E° = 1.36 V
Net: 2NaCl (l)  Cl2 (g) + 2Na(l) E° =

7. Electrolysis of aqueous solutions
What would happen if you put electricity into a solution of KI?
Possible oxidation reactions?
Possible reduction reactions?
Actual Reaction?

8. General rules in aqueous solutions
Reduction
6H2O + 2e-  H2 (g) + 2OH- E° = V
Oxidation
6H2O  O2 (g) + 4H3O+ + 4e- E° = V

9. Counting electrons

10. 1.50 amps flow through a Ag+(aq) solution for 15.0 min.
What mass of Ag metal is deposited?

11. Pb(s) + HSO4-(aq)  PbSO4(s) + H+(aq) + 2e-
The anode reaction in a lead storage battery is:
Pb(s) + HSO4-(aq)  PbSO4(s) + H+(aq) + 2e-
If a battery delivers 1.50 amp, and you have 454 g of Pb, how long will the battery last?

12. Recap Balancing Redox reactions Electrochemical cells Batteries
Standard Reduction Potential table
Corrosion
Nernst equation
Electrolysis
Molten
aqueous
Counting electrons

13. Acid Mine Drainage REDOX in the real world
FeS2 (pyrite) + O2  SO42- + Fe2+

15. 2Ag+ (aq) + Hg (l) ↔ 2Ag(s) + Hg2+ (aq)
Example
Calculate the equilibrium constant for:
2Ag+ (aq) + Hg (l) ↔ 2Ag(s) + Hg2+ (aq)
E° (V)
Hg2+ (aq) + 2e-  Hg (l)
Ag+ (aq) + e-  Ag(s)

16. Primary Batteries (non-rechargeable) Oxyride battery
E° = 1.7 V
Cathode: NiOOH + H2O + e-  Ni(OH)2 + OH- (1)
Anode: MnO2 (aq) + H2O + e-  MnO(OH) (s) + OH-
New battery
Vacuum pouring technology
Should last 2X longer than alkaline battery

17. Primary Batteries (non-rechargeable) Oxyride battery
Not responsible for this one
E° = 1.7 V
Cathode: NiOOH, MnO2
Anode: Zinc
New battery
Vacuum pouring technology
Should last 2X longer than alkaline battery