Question

Assertion: Mercury cell does not give steady potential.

Reason: In the cell reaction, ions are not involved in the solution.

(A). Both assertion & reason are f

(B). Both assertion and reason are true and reason is the correct explanation of assertion.

(C). Assertion is false but the reason is true.

(D). Assertion is true but the reason is false.

(E). Both assertion and reason are true but reason is not the correct explanation of assertion.

Answer 1

The correct option is (C) Assertion is false but the reason is true.

Assertion: Mercury cells give a steady potential because, they do not involve the movement of ions. Thus, the assertion is false.

The reactions inside a mercury cell are as follows:

At anode:

Zn(Hg) + 20H → ZnO(s) + H₂O + 2e−

At cathode:

HgO + H2O + 2e(−) → Hg(l) + 2OH

Over all reaction

Zn(Hg) + HgO(s) → ZnO(s) + Hg(l)

The cell potential value is ~1.35 V and remains constant throughout its life as they
do not involve any ion whose concentration varies during its lifetime. Thus, it gives a
steady potential throughout its life.

Thus, the reason is true.

Hence, the assertion is false, but the reason is true.