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Give reasons for the following.
Why does pink colour of aqueous solution disappear when warmed with oxalic acid solution in acidic…
Why does pink colour of aqueous $\text{KMnO}_4$ solution disappear when warmed with oxalic acid solution in acidic medium?
Answer
Answer
AIThe pink/purple colour of $\text{KMnO}_4$ is due to the permanganate ion ($\text{MnO}_4^-$). In acidic medium, $\text{MnO}_4^-$ oxidizes oxalic acid to $\text{CO}_2$ and is itself reduced to colourless $\text{Mn}^{2+}$ ions, causing the pink colour to discharge:
$2\text{MnO}_4^- + 5\text{C}_2\text{O}_4^{2-} + 16\text{H}^+ \longrightarrow 2\text{Mn}^{2+} + 10\text{CO}_2\uparrow + 8\text{H}_2\text{O}$
From ISC 2026 Chemistry Paper 1, question 10(ii).