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Question
Write the chemical equation for the preparation of 4 KMnO from 2. MnO Why does purple colour of acidified permanganate solution decolourise when it oxidises Fe2- to Fe3+ ?
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Solution
Chemical equations for the preparation of KMnO4 from MnO2
2MnO2 + 4KOH + O2 → 2K2MnO4 + 2H2O
`3MnO_4^2+4H -> 2MnO_4^- + 2 MnO_4^- + MnO_2 + 2H_2O `
\[\ce{ MnO_2 ->[Fused with oxidised][with air or KNO3]}MnO_4^{2-}\] maganate ion
\[\ce{ \underset{Manganate}{MnO_4^{2-}} ->[Electrolytic oxidation][in alkaline solution] MnO_4^- }\] permanganateion
Purple colour of acidified permanganate solution decolourise when it oxidises Fe2- + Fe3+
In acidic medium, Reduction
KMnO4 is behaving as oxidising Agent.
So, purple colour of acidified 4 KMnO solutions decolourises.
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