Q.ix. Write the electrode reactions when lead storage cell generates electricity. What are the anode and cathode and the electrode reactions during its recharging?

Step 1. During DISCHARGE, the lead accumulator functions as a galvanic cell: at the anode, spongy Pb is oxidised and precipitates as PbSO4, $Pb(s)+SO_4^{2-}(aq)\rightarrow PbSO_4(s)+2e^-$; at the cathode, PbO2 is reduced (in presence of H+) and also precipitates as PbSO4, $PbO_2(s)+4H^+(aq)+SO_4^{2-}(aq)+2e^-\rightarrow PbSO_4(s)+2H_2O(l)$.

Step 2. During RECHARGING, an external potential slightly above 2V is applied, and the cell functions as an electrolytic cell: the anode and cathode are INTERCHANGED, with the PbO2 electrode now the anode (+) and the Pb electrode now the cathode (–).

Step 3. The recharging anode reaction is the reverse of the discharge cathode reaction: $PbSO_4(s)+2H_2O(l)\rightarrow PbO_2(s)+4H^+(aq)+SO_4^{2-}(aq)+2e^-$. …

Give the discharge half reactions (galvanic mode) then explicitly reverse them and swap anode/cathode roles for the …

• Forgetting that anode/cathode SWAP their identity between discharge and recharge (the same physical PbO2 plate is c …