Question

Give the electrode reactions of the mercury cell.

Answer 1

At anode: \[\ce{Zn + 2OH- -> ZnO_{(s)} + H2O + 2e-}\]

At cathode: \[\ce{HgO_{(s)} + H2O + 2e- -> Hg_{(l)} + 2OH-}\]

Overall reaction: \[\ce{Zn + HgO_{(s)} ->  ZnO_{(s)} + Hg_{(l)}}\]

The anode is made of zinc-mercury amalgam. The cathode is a mixture of carbon and HgO. The cell uses a paste of KOH and ZnO as its electrolyte.