1.

Explain about the construction and uses of mercury button cell.

Answer»

SOLUTION :(i) Mercury button cell :
`{:("ANODE",:,"Zinc Amalgamated with mercury"),("Cathode",:,HgO " MIXED with graphite"),("Electrolyte",:,"Paste of KOH and ZnO"):}`
(ii) Oxidation occurs at anode :
`overset(2+)(HgO_(s)) + H_2O_((l)) + 2e^(-) to Hg_((l)) + 2OH_((aq))^(-)`
Overall reaction is
`Zn_((s)) + HgO_((s)) to ZnO_((s)) + Hg_((l))`
(iv) Cell emf : about 1.35 V
(v) Uses :
It has HIGHER capacity and longer life. It is used in pacemakers, electronic watches, cameras.
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