IMAT 2014 Q45 [Oxidation Numbers]

A battery has lead plates dipped in sulfuric acid. When charged, the positive plate is covered with PbO_2. After discharge both plates are covered with PbSO_4.

Which option below correctly describes the overall change in the oxidation number of the lead involved in the chemical reaction during discharge?

A. Positive plate: 4 → 2; Negative plate: 2 → 0
B. Positive plate: 4 → 2; Negative plate: 0 → 2
C. Positive plate: 4 → 0; Negative plate: 0 → 2
D. Positive plate: 4 → 1; Negative plate: 0 → 1
E. Positive plate: 4 → 1; Negative plate: 1 → 0