QJEEM22Ch0a15: JEE Main 2022 Chemistry - Class 12 JEEM22Ch0a15 Solution: In neutral or faintly alkaline medium, KMnO 4 being a powerful…

In neutral or Faintly alkaline medium, thiosulphate is oxidised almost quantitatively to sulphate ion according to reaction given below,

$8 \mathrm{MnO}_{4}^{-}+3 \mathrm{~S}_{2} \mathrm{O}_{3}^{2-}+\mathrm{H}_{2} \mathrm{O} \rightarrow 8 \mathrm{MnO}_{2}+6 \mathrm{SO}_{4}^{2-}+2 \mathrm{OH}^{-}$

Here the $\mathrm{Mn}$ changes from $\mathrm{Mn}^{+7}$ to $\mathrm{Mn}^{+4}$

Thus overall change in its oxidation number would be of 3 .