lecture 253/28/07. secondary batteries (rechargeable) nicad e° = 1.229 v cathode: 2nio(oh) (s) + 2h...
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Secondary Batteries (rechargeable)NiCad
E° = 1.229 V
Cathode: 2NiO(OH) (s) + 2H2O + 2e- 2Ni(OH)2 (s) +
2OH- Anode: Cd(s) + 2OH- - Cd(OH)2 (s) + 2e-
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-
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
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?
Electrolysis of molten salts
Cathode: 2Na+ (l) + 2e- 2Na(l) E° = -2.71 V
Anode:2Cl- (l) Cl2 (g) + 2e- E° = 1.36 V
Net: 2NaCl (l) Cl2 (g) + 2Na(l) E° =
Electrolysis of aqueous solutions
What would happen if you put electricity into a solution of KI?
Possible oxidation reactions?
Possible reduction reactions?
Actual Reaction?
General rules in aqueous solutions
Reduction 6H2O + 2e- H2 (g) + 2OH- E° = -0.8277 V
Oxidation 6H2O O2 (g) + 4H3O+ + 4e- E° =
1.229 V
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?
Recap
Balancing Redox reactions Electrochemical cells Batteries Standard Reduction Potential table
Corrosion Nernst equation Electrolysis
Molten aqueous
Counting electrons
Example
Calculate the equilibrium constant for:2Ag+ (aq) + Hg (l) ↔ 2Ag(s) + Hg2+ (aq)
E° (V)Hg2+ (aq) + 2e- Hg (l) 0.855Ag+ (aq) + e- Ag(s) 0.7994
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