Disproportionation Reaction in ClO2

Steps:

• Calculate oxidation state of Cl in ClO2: +4 (2O at -2 each, total molecule neutral).
• Identify Cl states in products: +3 in ClO2- (O2 at -4, charge -1), +5 in ClO3- (O3 at -6, charge -1).
• Compare: one Cl reduced (+4 to +3), one Cl oxidized (+4 to +5) per reaction.
• Confirm oxygen: remains -2 in OH-, H2O, ClO2-, ClO3- (no redox for O).

Why C is correct:

• Disproportionation occurs when the same element (Cl) is both oxidized and reduced, as shown by split oxidation states.

Why the others are wrong:

• A: Cl is both oxidized and reduced, but O oxidation states unchanged.
• B: Cl is both oxidized and reduced, but O not reduced.
• D: O oxidation states unchanged; only Cl varies.

Final answer: C