Maharashtra BoardEnglish MediumSTD 12 ScienceChemistryElectrochemistry4 Marks
Question
Write a note on Nickel-Cadmium (NICAD) cell.
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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, $NiO _2$ 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 : $Cd _{( s )}+2 OH ^{-}( aq ) \rightarrow Cd ( OH )_{2( s )}+2 e ^{-}$ (ii) Reduction at $Ni02 ( s$ ) cathode : $NiO _{2( s )}+2 H _2 O _{( l )}+2 e ^{-} \rightarrow Ni ( OH )_{2( s )}+2 OH ^{-}{ }_{( aq )}$ The overall cell reaction is the combination of above two reactions. $Cd _{( s )}+ NiO _{2( s )}+2 H _2 O _{( l )} \rightarrow Cd ( OH )_{2( s )}+ Ni ( OH )_{2( s )}$ (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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