In a mercury cell, zinc-mercury amalgam is used as an anode and carbon is used as a cathode. A paste of _______ is used as an electrolyte.

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RRB ALP Electronics Mechanic 23 Jan 2019 Official Paper (Shift 3)

Answer 1

In a mercury cell, the electrolyte used is typically a paste of potassium hydroxide (KOH) and mercury(II) oxide (HgO).
The paste serves as a source of hydroxide ions (OH-) that are needed to complete the electrochemical reaction occurring in the cell.
The reaction at the anode involves the oxidation of the zinc in the amalgam to form zinc ions (Zn²⁺) and electrons (e^-).

While at the cathode, the reduction of the mercury(II) oxide and the production of liquid mercury takes place.

Overall, the reaction can be represented as:

Zn(Hg) + HgO(s) + 2 KOH(aq) → ZnO(s) + Hg(l) + 2 K[Hg] + H2O(l)

where [Hg] represents a complex of mercury and potassium.