What is the change in oxidation number of Pb at positive electrode of lead accumulator acting as galvanic cell ?

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In a lead accumulator acting as a galvanic cell (discharging), the positive electrode acts as the cathode where reduction takes place. The reaction at the positive electrode is: PbO₂(s) + SO₄²⁻(aq) + 4H^+(aq) + 2e^- PbSO₄(s) + 2H₂O(l) The oxidation state of Pb in PbO₂ is +4 . The oxidation state of Pb in PbSO₄ is +2 . The oxidation number of Pb changes from +4 to +2 , which means it decreases by 2 . Answer: decreases by 2