Question

A depolarizer used in dry cell is

• A. Ammonium chloride
• B. Manganese dioxide
• C. Potassium oxide
• D. Sodium phosphate

Answer 1

The correct option is B

Manganese dioxide

The correct option is option D:

The explanation for the correct option:

1. Depolarizers are substances that are employed in primary cells to stop hydrogen gas bubbles from accumulating.
2. A battery depolarizer always acts as an oxidizer because it absorbs electrons during the cell's discharge.
3. A graphite rod or a metal electrode is covered in a low moisture electrolyte paste in a dry cell, which is made of a metal container. In most cases, the metal container will be made of zinc, whose base serves as a negative electrode (anode) and a positive electrode (carbon road) (cathode).
4. Manganese dioxide and a low moisture electrolyte, such as ammonium chloride paste, that can only produce $1.5\mathrm{V}$ of voltage and is irreversible, surround it.
5. The moistened electrolyte undergoes a reduction reaction that involves the elements manganese dioxide (${\mathrm{MnO}}_2$) and ammonium chloride (${\mathrm{NH}}_4\mathrm{Cl}$), with graphite acting as solid support for the reaction. $2{{\mathrm{NH}}_4}^{+}+2{\mathrm{MnO}}_2\to {\mathrm{Mn}}_2{\mathrm{O}}_3+2{\mathrm{NH}}_3+{\mathrm{H}}_2\mathrm{O}$
6. An oxidation reaction takes place on the zinc container, which acts as the anode. $\mathrm{Zn}\to {\mathrm{Zn}}^{+2}+2{\mathrm{e}}^{-}$
7. The most common dry cell is the zinc-carbon cell, commonly known as the Leclanche cell.
8. The dry cell uses manganese dioxide as a depolarizer.
9. Also ${\mathrm{MnO}}_2$ produces moisture keeping the solution moist so that ionic mobility increases.

Final answer: A depolarizer used in dry cells is manganese dioxide.