Question

Which liquid is used in a battery?

Answer 1

Hint: Dilute Sulphuric acid $(H_{2}S{O}_{4}in{H}_{2}O)$ is the liquid electrolyte which is used in batteries. Sulphuric acid is a strong acid which dissociates completely into ions in water. Owing to this property, sulphuric acid proceeds with the charging –discharging process smoothly in the battery.

Complete answer:
Approximately 30 % to 50 % sulphuric acid solution in water is used as electrolyte in batteries. Let us consider the lead-acid battery. In this battery, lead $(Pb)$ , lead oxide $(Pb{O}_2)$ are used as electrodes and dilute sulphuric acid is used as an electrolyte. In water, $H_{2}S{O}_4$ is completely dissociated and produces hydrogen ion $\left(H^{+}\right)$ and sulphate ion ${S{O}_4}^{2-}$. These ions are reacted with $Pb$ and $Pb{O}_2$ and produce $PbS{O}_4$ which is sparingly soluble in water. Hence, the concentration of $H_{2}S{O}_4$ in the water goes on decreasing. In this way, the battery gets discharged. On the other hand, during the charging process, $PbS{O}_4$ which is produced at both anode and cathode gets converted into $Pb$ and $Pb{O}_2$ with simultaneously generation of hydrogen ion $\left(H^{+}\right)$ and sulphate ion ${S{O}_4}^{2-}$ . Hence, the concentration of $H_{2}S{O}_4$ in the water goes on increasing and the battery gets charged.

Additional Information:
Besides certain advantages of using dilute sulphuric acid as electrolyte in batteries, it has few limitations which includes its corrosive nature and dangerous liquid to handle.

Note:
It is important to note that dilute sulphuric acid is used as liquid electrolyte in batteries. $H_{2}S{O}_4$ is a strong acid which dissociates completely in water and produces hydrogen ion $\left(H^{+}\right)$ and sulphate ion $(SO{4}^{2-})$ . These ions allow the proceeding of the charging –discharging process smoothly in the battery.