Final answer:
The electrode reactions in a lead storage cell involve lead and lead dioxide undergoing respective oxidation and reduction during discharge. When recharged, the reactions reverse, converting lead sulfate back to the original active materials. The anode is negative during discharge and positive during recharge, while the cathode is positive during discharge and negative during recharge. Option number b is correct.
Step-by-step explanation:
During the discharge of a lead storage cell, the anode undergoes oxidation while the cathode undergoes reduction. The half-reactions for each electrode during discharge are as follows:
- Anode (oxidation): Pb(s) + SO42-(aq) → PbSO4(s) + 2e-
- Cathode (reduction): PbO2(s) + 4H+(aq) + SO42-(aq) + 2e- → PbSO4(s) + 2H2O(l)
During recharging, the reactions are reversed. The lead sulfate on both electrodes is converted back to lead, lead dioxide, and sulfuric acid. This regeneration of active materials characterizes secondary batteries like the lead-acid battery.
Electrode Assignment during Discharge and Recharge
- Discharging:
- Anode: Lead (Pb), negative electrode
- Cathode: Lead dioxide (PbO2), positive electrode
- Recharging:
- Anode: Lead dioxide (PbO2), positive electrode
- Cathode: Lead (Pb), negative electrode
The ability of the lead-acid battery to be recharged makes it useful for starting, lighting, and ignition (SLI) in automobiles. The flow of electrons during the discharge provides the energy necessary to power electrical components.