VI. Applications of Electrochemical Cells: (Batteries)

1. The Dry Cell

Carbon (Cathode)

Zinc (Anode)

Paste of MnO2 , NH4Cle-

Anode: Zn Zn2+ + 2e-

Cathode: 2MnO2 + 2NH4+ + 2e- 2MnO(OH) + 2NH3

Ecell = 1.5 V Poor diffusion of products. The alkaline battery is similar, but includes a salt bridge of

KOH and more reactants.

2. Silver Oxide Battery

KOHe-

Anode: Zn Zn2+ + 2e-

Cathode: Ag2O + 2e- 2Ag + OH-

Used for watches, cameras, hearing aids…

Ag2O

Zn

3. Lead Storage Battery

PbO2

e-

Anode: Pb + SO42- PbSO4 + 2e-

Cathode: PbO2 + 4H+ + SO42- + 2e- PbSO4 + 2H2O

Reactions are reversed by applying an external voltage.

Pb

fill cap

H2SO4

Ecell = 2.0 V

6 are connected in series = 12 V

4. Fuel Cells

O2 (air)

e-

Anode: H2 + 2OH- 2H2O + 2e-

Cathode: O2 + 2H2O + 4e- 4OH-

Produces electricity and water.

H2

KOHPorous carbon

Overall: 2H2 + O2 2H2O