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Which of the following reactions are disproportionation reactions? (A) Cu+ → Cu2+ + Cu (B) 3MnO4^2− + 4H+ → 2MnO4− + MnO2 + 2H2O (C) 3KMnO4 → K2MnO4 + MnO2 + O2 (D) 2MnO4− + 3Mn2+ + 2H2O → 5MnO2 + 4H+

1. (B), (C), (D)
2. (A), (D)
3. (A), (B)
4. (A), (B), (C)

Correct answer: (A), (B)

Solution

Disproportionation reactions involve a single element undergoing both oxidation and reduction simultaneously. In options (A) and (B), copper and manganese change their oxidation states in a way that fits this definition, while the other options do not exhibit this characteristic.

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