alleryRusting of iron is an electrochemical phenomenon. At the cathodic spot, the reaction is:
AFe²⁺ + 2e⁻ → Fe
BO₂(g) + 4H⁺(aq) + 4e⁻ → 2H₂O(l)
C2Fe²⁺ → 2Fe³⁺ + 2e⁻
DFe → Fe²⁺ + 2e⁻
Answer & Solution
Correct answer: B. O₂(g) + 4H⁺(aq) + 4e⁻ → 2H₂O(l)
**Rusting:** at an **anodic spot** Fe is oxidised (Fe → Fe²⁺ + 2e⁻).
Electrons flow through the metal to a **cathodic spot** where atmospheric O₂ (with H⁺ from dissolved CO₂/H₂CO₃) is reduced: **O₂ + 4H⁺ + 4e⁻ → 2H₂O**.
Net cell potential ≈ +1.67 V.
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