Question

Technician A says that both soft and hard sulfate can be driven from the plates, bringing the battery back into service. Technician B says that leaving a battery in a state of discharge for a long time hardens and prevents sulfate from being driven from the plates.

Answer 1

Lead-acid car batteries accumulate lead sulfate during discharge, which can be removed by recharging, restoring the battery's functionality. Technician A believes sulfates can be removed to revive a battery, while Technician B maintains that prolonged discharge leads to hardened sulfate that is difficult to remove, hindering recharging efficiency.

Step-by-step explanation:

The subject of the question is car batteries, specifically the rechargeable lead-acid batteries used to start an engine. The discussion centers on the recovery of a battery's function by reversing the sulfation process, where lead sulfate (PbSO4) accumulates on the battery plates during discharge.

Technician A suggests that both soft and hard sulfate can be removed from the plates, potentially reviving the battery. Conversely, Technician B argues that a battery left in a discharged state for an extended period will experience hardened sulfate on the plates, which becomes difficult to remove and negatively impacts the battery’s ability to be recharged.

In chemistry terms, a car’s alternator can reverse the discharge reaction, as shown by the recharging reaction 2PbSO4(s) + 2H2O(l) → Pb(s) + PbO2(s) + 4H+(aq) + 2SO42-(aq), which restores the lead, lead (IV) oxide, and sulfuric acid essential for the battery's function.

However, recharging efficiency might not be 100%, as some lead (II) sulfate detaches from the electrodes and collects at the bottom of the cells, potentially causing problems over time.