Tamilnadu BoardEnglish MediumSTD 12ChemistryElectro Chemistry3 Marks
Question
Describe the composition of anode and cathode in a mercury cell. Write the electrode reactions for this cell.
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Answer
Mercury cell: It consists of zinc mercury amalgam as anode, a paste of $HgO$ and Carbon black is used as cathode. The electrolyte is a paste of KOll and $ZnO$. At anode: $Zn$ (amalgam) $+2 OH ^{-} \rightarrow ZnO ( s )+ H _2 O ( l )+2 e ^{-}$ At cathode: $HgO ( s )+ H _2 O +2 e ^{-} \rightarrow Hg (1)+2 OH ^{-}$ The net reaction $: Zn ($ amalgam $)+ HgO ( s ) \rightarrow ZnO ( s )+ Hg ( l )$
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