1.

Write the reactions taking place in anode and cathode of a mercury button cell. Give the over all redox reaction of the cell with the emf generation.

Answer»

Solution :(i) OXIDATION occurs at anode :
`overset(0)(Zn_((s)))+underset("from KOH")(2OH_((aq))^(-)) rarr overset(+2)(ZnO_((s)))+H_(2)O(L)+2e^(-)`
(ii) REDUCTION occurs at cathode :
`overset(+2)(HgO_((s)))+H_(2)O(l)+2e^(-) rarr overset(0)(HG(l))+2OH_((aq))^(-)`
(iii) Overall reaction :
`Zn_((s))+HgO_((s)) rarr ZnO_((s))+Hg(l)`
(iv) Cell emf : about 1.35 V.


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