Question

Which among the following is a standard cell?
A) Daniel cell
B) Cadmium cell
C) Leclanche cell
D) Lead accumulator

Answer 1

The Standard cell is constructed with the basic materials- mercury, cadmium, sulfuric acid, and water- are all purified by distillation.

Complete step by step solution:
Among the given cells only Cadmium cell is a standard cell. Since a standard cell is made up of mercury, cadmium sulfuric acid and water, therefore a cadmium cell is considered as a standard cell. For a cell to be an ideal standard cell it must follow some conditions. Some of them are:
The cell must be made up of pure materials and should be reproducible.
When no current is flowing through it, there should not be any chemical reaction taking place in a cell.
When the cell is thermally in the same state, it should produce the same emf as earlier at the same temperature..
When current is passed through the cell, its emf may change but it should recover rapidly.
First and last conditions are followed by the cadmium cell. Therefore it is considered a standard cell. Other cells either do not follow ideal conditions or are not made up of pure materials. So they are not standard cells. A cadmium cell is a rechargeable cell. Compared with many primary batteries cadmium cells are heavy and have comparatively limited energy density.

Note: One of the major differences between standard cell and primary cell is that standard cells are rechargeable whereas primary cells are not. Daniel, leclanche cell and lead accumulator are non rechargeable. Also they are not made up of mercury or cadmium.