Question

What happens to the concentration of ${\mathrm{H}}_2{\mathrm{SO}}_4$ during the working of lead-storage battery?

Answer 1

Secondary cells

• Secondary cells generate current as a result of reversible chemical processes.
• When current is sent through it, it changes electrical energy into chemical energy.
• When current is pulled from it, it converts chemical energy back into electrical energy.
• Examples: Phone batteries, lead storage batteries, and some AA/AAA batteries too which are rechargeable.

Lead storage battery

• When a lead-acid battery discharges, Lead sulfate $\left({\mathrm{PbSO}}_4\right)$ is applied to both plates of the battery, covering both.
• Water is produced during the reaction at the Lead oxide $\left({\mathrm{PbO}}_2\right)$ plate, which causes the specific gravity of the sulfuric acid solution to fall.
• As a result, the rate of reaction slows, suggesting that the potential difference between the plates also narrows throughout the discharging process.
• A lead-acid battery's sulfuric acid $\left({\mathrm{H}}_2{\mathrm{SO}}_4\right)$ concentration contributes to the production of the electrolyte solution, which enables current passage between the two plates.
• During the working of the lead storage battery, the concentration of ${\mathrm{H}}_2{\mathrm{SO}}_4$ decreases.
• The reaction is as follows:

$\mathrm{Pb}\left(\mathrm{s}\right)+{\mathrm{PbO}}_2\left(\mathrm{s}\right)+2{\mathrm{H}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)\to 2{\mathrm{PbSO}}_4\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$