Question
Explain about the construction and uses of mercury button cell.
✓
Answer
1. Mercury button cell:
Anode: Zinc Amalgamated with mercury
Cathode: $HgO$ mixed with graphite
Electrolyte: Paste of $KOH$ and $ZnO$.
2. Oxidation occurs at anode:
$Zn _{( s )}+2 OH ^{-}{ }_{( aq )} \rightarrow ZnO _{( s )}^{+2}+ H _2 O _{( l )}+2 e ^{-}$
3. Reduction occurs at cathode
$\stackrel{+2}{ HgO _{( s )}}+ H _2 O _{( l )}+2 e ^{-} \rightarrow \stackrel{\circ}{ Hg _{( l )}}+2 OH _{( aq )}^{-}$
$Hg ( s )$
$+2 OH _{( aq )}^{-}$
Overall reaction is
$Zn _{( s )}+ HgO _{( s )} \rightarrow ZnO _{( s )}+ Hg _{(1)}$
5. Uses:
It has higher capacity and longer life. It is used in pacemakers, electronic watches, cameras.
Anode: Zinc Amalgamated with mercury
Cathode: $HgO$ mixed with graphite
Electrolyte: Paste of $KOH$ and $ZnO$.
2. Oxidation occurs at anode:
$Zn _{( s )}+2 OH ^{-}{ }_{( aq )} \rightarrow ZnO _{( s )}^{+2}+ H _2 O _{( l )}+2 e ^{-}$
3. Reduction occurs at cathode
$\stackrel{+2}{ HgO _{( s )}}+ H _2 O _{( l )}+2 e ^{-} \rightarrow \stackrel{\circ}{ Hg _{( l )}}+2 OH _{( aq )}^{-}$
$Hg ( s )$
$+2 OH _{( aq )}^{-}$
Overall reaction is
$Zn _{( s )}+ HgO _{( s )} \rightarrow ZnO _{( s )}+ Hg _{(1)}$
5. Uses:
It has higher capacity and longer life. It is used in pacemakers, electronic watches, cameras.
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