Question

Which of the following is true for a dry cell? a) It contains boric acid, which is a solid acid. b) The graphite rod does not undergo reduction, even though it is the cathode. c) It can be recharged many times. d) all of the above

Answer 1

Answer: b) The graphite rod does not undergo reduction, even though it is the cathode.

Explanation: Dry cell, is compact form of Leclanche cell. It consists of a cylindrical zinc container which acts as anode. A graphite rod which acts as cathode is placed in the center and is coated with powdered
`MnO_2` and carbon. The in between space is filled with a paste of
`NH_4Cl` and
`ZnCl_2`

At anode: Oxidation

`Zn\rightarrow Zn%{2+}+2e^-`

At cathode: Reduction

`2MnO_2+2NH_4^++2e^-\rightarrow Mn_2O_3+2NH_3+H_2O`

Thus it is
`MnO_2` and not graphite which undergoes reduction.

Answer 2

A dry cells has b) The graphite rod does not undergo reduction, even though it is the cathode.