Assertion : Mercury cell does not give steady potential.
Reason : In the cell reaction, ions are not involved in solution.
(v) Assertion is false but reason is true.
The overall reaction of Mercury cell is represented as
Zn(Hg) + HgO(S) → ZnO(S) + Hg(l)
The cell potential value is ~1.35V and remains constant throughout its life as they do not involve any ion whose concentration varies during its lifetime. Thus, gives a steady potential throughout its life.