Question

What is a secondary cell?

Answer 1

Hint: Secondary cell is categorised under the electrochemical cells, or we can say the dry cell. Secondary cells can be defined on the basis of reversible nature in comparison to the primary cell, and many more factors can be considered.

Complete step by step solution:
> Now, let us discuss the secondary cell. As mentioned it is categorised under the dry cell.
In other terms, we can also say it is a type of battery. The device used for the conversion of chemical energy to the electrical energy.
Thus, a battery is similar to the galvanic cell. If we talk about the types of battery; it is categorised into two types i.e. primary cell, and a secondary cell.
> Now, we will further discuss the secondary cell. It can be recharged with the help of current passing through the electrodes in the opposite direction.
> We can simplify the passing of current from the negative terminal to the positive terminal.
> If we consider the reversible nature of a secondary cell, then it is reversible, as we already discussed it is recharged by passing the current.
- Talking about the other factors i.e. these have low energy density, and mainly composed of molten salts, and the wet cells.
- Thus, the chemical reaction occurring in the cell is too reversible, and is very high in cost.
The example of a secondary cell is nickel-cadmium cell.
> If we talk about the nickel-cadmium cell, then the first reaction will be at anode, second reaction at cathode. Let us write the reactions:
At anode:
Cd(s) + 2OH$^{-}$ $\rightarrow$ Cd(OH)$_2$ + 2e$^{-}$
At cathode:
NiO$_2$ + 2e$^{-}$ + 2H$_2$O $\rightarrow$ Ni(OH)$_2$ + 2OH$^{-}$ (aq)
From these two reactions, we can write the overall reaction that will be written as:
Cd(s) + NiO$_2$ (s) + 2H$_2$O $\rightarrow$ Cd(OH)$_2$ + Ni(OH)$_2$
So, we can say that at the anode, we get cadmium hydroxide, and at cathode we get nickel hydroxide.
In the last, we can conclude that the secondary cell is a type of electrical cell where redox reaction occurs, and depicts the reversible nature.

Note: Don’t get confused between the primary cell, and secondary cell while defining them. We already talked about the secondary cell. The primary cell is irreversible in nature, and cannot be recharged again after it is used for one time.