1.

Unlike dry cell, the mercury cell has a constant cell potential throughout its useful life. Why ?

Answer»

SOLUTION :* Because, in total reaction of mercury cell no ion is taking part in reaction.
* In mercury cell, zinc amalgum is used as anode and HGO and carbon PEST is used as cathode. So the chemical reaction occur on electrodes are as follows:
Cathode: `HgO+H_(2)O+2e^(-) to Hg_((L))+2OH^(-)`
Anode : `underline(Zn(Hg)+2OH^(-) ZnO_((S))+H_(2)O+2e^(-))`
Total reaction : `Zn(Hg)+HgO_((S)) to ZnO_((S))+Hg_((l))`
* During whole LIFE span the cell potential of 1.35 V is constant because, no ions are present in overall cell reaction.


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