1.

Write a note on Nickel-Cadmium (NICAD) cell.

Answer»

(1) Nickel-Cadminum (NICAD) cell is a secondary dry cell.

(2) It is rechargable, hence it is a reversible cell.

(3) It consists of a cadmium electrode in contact with an alkali and acts as anode while nickel (IV) oxide, NiO2 in contact with an alkali acts as cathode. The alkali used is moist paste of KOH.

(4) Reactions in the cell :

(i) Oxidation at cadmium anode : 

Cd(s) + 2OH-(aq) → Cd(OH)2(s) + 2e-

(ii) Reduction at NiO2(s) cathode :

NiO2(s) + 2H2O(I) + 2e- → Ni(OH)2(s) + 2OH-(aq)

The overall cell reaction is the combination of above two reactions.

Cd(s) + NiO2(s) + 2H2O(I) → Cd(OH)2(s) + Ni(OH)2(s)

(5) Since the net cell reaction doesn’t involve any electrolytes but solids, the voltage is independent of the concentration of alkali electrolyte.

(6) The cell potential is about 1.4 V.

(7) This cell has longer life than other dry cells.


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