Answer
Balanced Half-Reactions for Acidic Redox System Involving Lead (Pb)
Step 1: Identify the species being oxidized and reduced.
PbO2 + SO42− → PbSO4
Pb + SO42− → PbSO4
– In the first reaction, PbO₂ (Pb⁴⁺) is reduced to Pb²⁺ in PbSO₄.
– In the second, Pb⁰ is oxidized to Pb²⁺ in PbSO₄.
Step 2: Write and balance the half-reactions.
Oxidation Half-Reaction (Pb is oxidized):
Pb → Pb2+ + 2e⁻
– Pb loses 2 electrons, going from 0 to +2 oxidation state.
Reduction Half-Reaction (PbO₂ is reduced):
PbO2 + SO42− + 4H+ + 2e⁻ → PbSO4 + 2H2O
– PbO₂ is reduced from Pb⁴⁺ to Pb²⁺, combining with SO₄²⁻.
– Water and H⁺ balance the oxygen and hydrogen atoms in acidic solution.
Final Answer: Identified Half-Reactions
- Oxidation: Pb → Pb²⁺ + 2e⁻
- Reduction: PbO₂ + SO₄²⁻ + 4H⁺ + 2e⁻ → PbSO₄ + 2H₂O