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Topic: Oxidation and reduction, oxidation number· Redox Reactions and Electrochemistry

Which of the following reactions are disproportionation reaction ?(a) 2Cu^+ → Cu^2+ + Cu^0(b) 3MnO_4^2- + 4H^+ → 2MnO_4^- + MnO_2 + 2H_2O(c) 2KMnO_4 Δ K_2MnO_4 + MnO_2 + O_2(d) 2MnO_4^- + 3Mn^2+ + 2H_2O → 5MnO_2 + 4H^Select the correct option from th…

Which of the following reactions are disproportionation reaction ?

(a) \(2Cu^{+} \to Cu^{2+} + Cu^{0}\)

(b) \(3MnO_4^{2-} + 4H^{+} \to 2MnO_4^{-} + MnO_2 + 2H_2O\)

(c) \(2KMnO_4 \xrightarrow{\Delta} K_2MnO_4 + MnO_2 + O_2\)

(d) \(2MnO_4^{-} + 3Mn^{2+} + 2H_2O \to 5MnO_2 + 4H^{\oplus}\)

Select the correct option from the following :

1. (a) and (b) only

2. (a), (b) and (c)

3. (a), (c) and (d)

4. (a) and (d) only

1 answer

Best answer

Answer: 1. (a) and (b) only

A disproportionation reaction is one in which the same species is both oxidised and reduced.

  • (a) \(\mathrm{Cu^+ \to Cu^{2+} + Cu^0}\): Cu goes +1 to +2 and +1 to 0. Disproportionation.
  • (b) \(\mathrm{MnO_4^{2-}}\) (+6) goes to \(\mathrm{MnO_4^-}\) (+7) and \(\mathrm{MnO_2}\) (+4). Disproportionation.
  • (c) \(\mathrm{KMnO_4}\) (+7) goes to \(\mathrm{K_2MnO_4}\) (+6) and \(\mathrm{MnO_2}\) (+4) while oxygen is oxidised to \(\mathrm{O_2}\). Mn is only reduced, so this is not disproportionation.
  • (d) Mn(+7) and Mn(+2) both form Mn(+4): this is the reverse, comproportionation.

Only (a) and (b), option (1).

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report
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