In mildly alkaline medium, thiosulphate ion is oxidized by $\mathrm{MnO}_{4}^{-}$ to "A". The oxidation state of sulphur in 'A' is ____

JEE Main · 2021 · 26 Feb 2021 · Shift 2 · Redox Reactions and Electrochemistry

In mildly alkaline medium, thiosulphate ion is oxidized by

MnO_{4}^{-}

to "A". The oxidation state of sulphur in 'A' is ____

Answer: 6

In mildly alkaline solution permanganate oxidises thiosulphate the whole way to sulphate:

8 Mn O_{4}^{-} + 3 S_{2} O_{3}^{2 -} + H_{2} O \to 8 Mn O_{2} + 6 S O_{4}^{2 -} + 2 O H^{-}

In the sulphate ion the four oxygen atoms account for

4 \times (- 2) = - 8

while the ion itself carries a charge of

- 2

, so the sulphur atom must be

+ 6

. The oxidation state of sulphur in the product is

+ 6

JEE Main · 2021 · 26 Feb 2021 · Shift 2 · Integer answer