Question

When a lead storage battery is discharged, then:

Answer 1

Lead storage battery:

• In a lead storage battery, the electrodes are the lead grids and dilute Sulfuric acid (${\mathrm{H}}_2{\mathrm{SO}}_4$) is the electrolyte.
• When the battery discharges, the lead at the anode gets oxidized.

Discharge of lead storage battery:

• When the lead storage battery is discharged, Sulfuric acid is consumed and water is created.
• The sulfuric acid is depleted which causes the electrolyte to become water.
• Charging is stopped and the Sulfate is returned to the acid.
• The overall cell reaction is as follows:

$\underset{\left(\mathrm{Lead}\right)}{\mathrm{Pb}\left(\mathrm{s}\right)}+\underset{\left(\mathrm{Lead}\mathrm{oxide}\right)}{{\mathrm{PbO}}_2\left(\mathrm{s}\right)}+\underset{\left(\mathrm{Sulfuric}\mathrm{acid}\right)}{2{\mathrm{H}}_2{\mathrm{SO}}_4(\mathrm{aq}})\to \underset{\left(\mathrm{Lead}\mathrm{sulfate}\right)}{2{\mathrm{PbSO}}_4\left(\mathrm{s}\right)}+\underset{\left(\mathrm{Water}\right)}{2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}$