Which of the given reactions is not an example of disproportionation reaction?
- (A)2H₂O₂ → 2H₂O + O₂
- (B)2NO₂ + H₂O → HNO₃ + HNO₂
- (C)MnO₄⁻ + 4H⁺ + 3e⁻ → MnO₂ + 2H₂O✓ Correct
- (D)3MnO₄²⁻ + 4H⁺ → 2MnO₄⁻ + MnO₂ + 2H₂O
Answer: (C)
Solution
A disproportionation reaction is one in which the same element undergoes both oxidation and reduction simultaneously.
Answer: (C).
- (A) 2H₂O₂ → 2H₂O + O₂: Oxygen goes from -1 (in H₂O₂) to -2 (in H₂O) and 0 (in O₂). Disproportionation.
- (B) 2NO₂ + H₂O → HNO₃ + HNO₂: Nitrogen goes from +4 (in NO₂) to +5 (in HNO₃) and +3 (in HNO₂). Disproportionation.
- (C) MnO₄⁻ + 4H⁺ + 3e⁻ → MnO₂ + 2H₂O: Mn goes from +7 to +4. This is only reduction, not disproportionation.
- (D) 3MnO₄²⁻ + 4H⁺ → 2MnO₄⁻ + MnO₂ + 2H₂O: Mn goes from +6 to +7 and +4. Disproportionation.
Answer: (C).
JEE Main · 2022 · 26 Jul 2022 · Shift 1 · Single correct option