Chemistry - Electrochemistry Question with Solution | TestHub

During the discharging of a lead accumulator, the positive electrode acts as a cathode where ${\mathrm{PbO}}_2$ is reduced to ${\mathrm{PbSO}}_4$.

During recharging, the cell operates as an electrolytic cell and the reactions are reversed. The positive electrode is connected to the positive terminal of the external DC source and acts as an anode, where oxidation takes place.

The reaction at the positive electrode during recharging is:
${\mathrm{PbSO}}_4(s)+2{\mathrm{H}}_2\mathrm{O}(l)\to {\mathrm{PbO}}_2(s)+4{\mathrm{H}}^{+}(aq)+{\mathrm{SO}}_4^{2-}(aq)+2e^{-}$

Thus, ${\mathrm{PbSO}}_4$ is oxidised to ${\mathrm{PbO}}_2$.

Answer: ${\mathrm{PbSO}}_4$ is oxidised to ${\mathrm{PbO}}_2$