Mention the reactions occurring at (i) anode (ii) cathode, during working of a mercury cell. Why does the voltage of a mercury cell remain constant during operation ?

Explanation

The cell reaction are as follows:
`{:("Anode", Zn(Hg) + 2OH^(-) to ZnO(s) + H_(2)O(l) + 2e^(-)),("Cathode", HgO(s) + H_(2)O(l) + 2e^(-) to Hg(l) + 2OH^(-)),("Net reaction", Zn(Hg) + HgO(s) to ZnO(s) +Hg(l)):}`
Voltage of the mercury cell remains constant because ions are not involved in the net reaction.