Question
Write note on Mercury cell (Zn-Hg)
✓
Answer
→ Mercury cell, suitable for low current devices like hearing aids, watches, etc.
→ It consists of zinc - mercury amalgam as anode and a paste of HgO and carbon as the cathode.
→ The electrolyte is a paste of KOH and ZnO . The electrode reactions for the cell are given below.
Anode : $Zn ( Hg )+2 OH ^{-} \rightarrow ZnO ( s )+ H _2 O +2 e ^{-}$
Cathode : $HgO + H _2 O +2 e ^{-} \rightarrow Hg (l)+2 OH ^{-}$
→ The overall reaction is represented by $Zn ( Hg )+ HgO ( s ) \rightarrow ZnO ( s )+ Hg (l)$
→ The cell potential is approximately 1.35V and remains constant during its life as the overall reaction does not involve any ion in solution whose concentration can change during its life time.
→ It consists of zinc - mercury amalgam as anode and a paste of HgO and carbon as the cathode.
→ The electrolyte is a paste of KOH and ZnO . The electrode reactions for the cell are given below.
Anode : $Zn ( Hg )+2 OH ^{-} \rightarrow ZnO ( s )+ H _2 O +2 e ^{-}$
Cathode : $HgO + H _2 O +2 e ^{-} \rightarrow Hg (l)+2 OH ^{-}$
→ The overall reaction is represented by $Zn ( Hg )+ HgO ( s ) \rightarrow ZnO ( s )+ Hg (l)$
→ The cell potential is approximately 1.35V and remains constant during its life as the overall reaction does not involve any ion in solution whose concentration can change during its life time.
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