Final answer:
In a lead storage battery, the reduced substance during discharge is lead (IV) oxide (PbO₂). The batteries are rechargeable, with lead (IV) oxide being regenerated during the recharging process.
Step-by-step explanation:
The substance that is reduced in a lead storage battery is lead (IV) oxide (PbO₂). During the discharge process of the battery, the redox reactions occur at the electrodes. At the cathode, which is the positive electrode, lead (IV) oxide (PbO₂) undergoes a reduction reaction to form lead (II) sulfate (PbSO₄) and releases electrons. This process can be reversed during recharging, wherein lead (IV) oxide is regenerated from lead (II) sulfate.
Lead storage batteries, commonly used in cars, are widely known for being rechargeable. These batteries consist of multiple cells, and each cell typically produces about 2 volts. Over time, as the reaction proceeds, solid lead (II) sulfate builds up on the plates, and the sulfuric acid concentration decreases. However, the car's generator can reverse this process to recharge the battery, effectively regenerating the lead, lead (IV) oxide, and sulfuric acid needed for the battery's operation.