The following statements describe various properties of a Mercury cell:
(A) It converts energy of combustion into electrical energy
(B) It is rechargeable
(C) The cell reaction involved is $Zn(Hg) + HgO(s) → ZnO(s) + Hg(l)$
(D) It is a low current device used in hearing aids
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (C) and (D) only
|
Statement |
Status |
Reason |
|
(A) It converts energy of combustion into electrical energy |
Incorrect |
This describes a Fuel Cell (like the $\text{H}_2\text{-}\text{O}_2$ fuel cell), which converts the chemical energy of a fuel ($\text{H}_2$) and an oxidant ($\text{O}_2$) into electrical energy. The mercury cell converts stored chemical energy into electrical energy. |
|
(B) It is rechargeable |
Incorrect |
The mercury cell is a Primary Cell, meaning the chemical reactions are irreversible. It is designed for single-use and cannot be recharged. |
|
(C) The cell reaction involved is $\text{Zn}(\text{Hg})+\text{HgO}(\text{s})\to\text{ZnO}(\text{s})+\text{Hg}(\text{l})$ |
Correct |
This is the overall, net reaction for the mercury cell (or zinc-mercuric oxide cell). It shows the oxidation of the Zinc amalgam ($\text{Zn}(\text{Hg})$) and the reduction of Mercuric oxide ($\text{HgO}$). |
|
(D) It is a low current device used in hearing aids |
Correct |
Mercury cells are typically small, button-shaped batteries designed for low-current devices like watches, calculators, and hearing aids. They are valued for their constant voltage output (approximately $1.35 \text{ V}$) over a long period. |