vi.applications of electrochemical cells: (batteries) 1.the dry cell carbon (cathode) zinc (anode)...
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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
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