Thiosulphate reacts differently with iodine and bromine in the reaction given below : $2 \mathrm{~S}_{2} \mathrm{O}_{3}^{2-}+\mathrm{I}_{2} \rightarrow \mathrm{~S}_{4} \mathrm{O}_{6}^{2-}+2 \mathrm{I}^{-}$ $\mathrm{S}_{2} \mathrm{O}_{3}^{2-}+5 \mathrm{Br}_{2}+5 \mathrm{H}_{2} \mathrm{O} \rightarrow 2 \mathrm{SO}_{4}^{2-}+4 \mathrm{Br}^{-}+10 \mathrm{H}^{+}$ Which of the following statement justifies the above dual behaviour of thiosulphate?

(C) Bromine is a stronger oxidant than iodine

(A) Bromine undergoes oxidation and iodine undergoes reduction by iodine in these reactions

(B) Thiosulphate undergoes oxidation by bromine and reduction by iodine in these reaction

(D) Bromine is a weaker oxidant than iodine

JEE Main · 2024 · 08 Apr 2024 · Shift 1 · Redox Reactions and Electrochemistry

Thiosulphate reacts differently with iodine and bromine in the reaction given below :

2 S_{2} O_{3}^{2 -} + I_{2} \to S_{4} O_{6}^{2 -} + 2 I^{-}

S_{2} O_{3}^{2 -} + 5 Br_{2} + 5 H_{2} O \to 2 SO_{4}^{2 -} + 4 Br^{-} + 10 H^{+}

Which of the following statement justifies the above dual behaviour of thiosulphate?

(A)Bromine undergoes oxidation and iodine undergoes reduction by iodine in these reactions
(B)Thiosulphate undergoes oxidation by bromine and reduction by iodine in these reaction
(C)Bromine is a stronger oxidant than iodine✓ Correct
(D)Bromine is a weaker oxidant than iodine

Answer: (C)

With

I_{2}

, sulphur in

S_{2} O_{3}^{2 -}

goes

+ 2 \to + 2.5

(mild oxidation, forms tetrathionate); with

B r_{2}

it goes

+ 2 \to + 6

(forms sulphate). The stronger oxidant

B r_{2}

drives the deeper oxidation, i.e. bromine is a stronger oxidant than iodine. Option (3).

JEE Main · 2024 · 08 Apr 2024 · Shift 1 · Single correct option