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When thiosulphate is oxidized quantitatively by KMnO4 in a neutral or slightly alkaline medium, the product formed is

1. SO3²−
2. SO4²−
3. SO2
4. SO5²−

Correct answer: SO4²−

Solution

In neutral/faintly alkaline medium KMnO4 oxidises thiosulphate quantitatively to sulphate: 8MnO4- + 3S2O3^2- + H2O -> 8MnO2 + 6SO4^2- + 2OH-. The product ion is SO4^2-.

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