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Question
When \[\ce{KMnO4}\] solution is added to oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after some time because ______.
Options
\[\ce{CO2}\] is formed as the product.
Reaction is exothermic.
\[\ce{MnO^{-}4}\] catalyses the reaction.
\[\ce{MnO^{2+}}\] acts as autocatalyst.
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Solution
When \[\ce{KMnO4}\] solution is added to oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after some time because \[\ce{MnO^{2+}}\] acts as autocatalyst.
Explanation:
When \[\ce{KMnO4}\] solution is added to oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after some time because \[\ce{Mn^{2+}}\] acts as an autocatalyst.
Reduction half \[\ce{Mno^{-}4 + 8H^+ + 5e^- -> Mn^{2+} + 4H2O] × 2}\]
Oxidation half \[\ce{C2O^{2-}4 -> 2CO2 + 2e] × 5}\]
Overall equation \[\ce{2Mno^{-}4 + 16H^+ + 5C2O^{2-}4 -> 2Min^{2+} + 10CO2 + 8H2O}\]
End point of this reaction Colourless to light pink.
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