COMEDK 2025 Evening Solved Paper

Concept:A disproportionation reaction is a redox reaction where the same element undergoes both oxidation and reduction.Explanation:Check each option to see if the same element is both oxidized and reduced.For option A: $2\mathrm{H}_2\mathrm{O}_2 \rightarrow 2\mathrm{H}_2\mathrm{O} + \mathrm{O}_2$Oxygen in $\mathrm{H}_2\mathrm{O}_2$ is in $-1$ oxidation state.In $\mathrm{H}_2\mathrm{O}$, oxygen is $-2$ (reduction).In $\mathrm{O}_2$, oxygen is $0$ (oxidation).So the same element (oxygen) is both reduced and oxidized — this is a disproportionation reaction.For option B: $2\mathrm{KMnO}_4 \rightarrow \mathrm{K}_2\mathrm{MnO}_4 + \mathrm{MnO}_2 + \mathrm{O}_2$Manganese goes from $+7$ to $+6$ and $+4$ (only reduction).Oxygen goes from $-2$ to $0$ (only oxidation).No single element undergoes both changes — not disproportionation.For options C and D: These are redox reactions between different elements (Mn vs. I, Cl vs. I), not self-redox.Thus, only option A satisfies the definition.Answer:Option A: $2\mathrm{H}_2\mathrm{O}_2 \rightarrow 2\mathrm{H}_2\mathrm{O} + \mathrm{O}_2$