Thiosulphate reacts differently with iodine and bromine in the reactions given below: \ $ 2 \mathrm

Question

Thiosulphate reacts differently with iodine and bromine in the reactions given below: \ $ 2 \mathrm{~S}_2 \mathrm{O}_3^{2-}+\mathrm{I}_2 \longrightarrow \mathrm{~S}_4 \mathrm{O}_6^{2-}+2 \mathrm{I}^{-} $\ $ \mathrm{S}_2 \mathrm{O}_3^{2-}+2 \mathrm{Br}_2+5 \mathrm{H}_2 \mathrm{O} \longrightarrow 2 \mathrm{SO}_4^{2-}+2 \mathrm{Br}^{-}+10 \mathrm{H}^{+} $ \ Which of the following statements is correct?\ I. Bromine is a stronger oxidant than iodine. \II. Bromine is a weaker oxidant than iodine. \III. Thiosulphate undergoes oxidation by bromine and reduction by iodine in these reactions. \IV. Bromine undergoes oxidation and iodine undergoes reduction in these reactions.

Professor PC Thomas Classes · Answer

(a) : $\mathrm{Br}_2$ oxidises S of $\mathrm{S}_2 \mathrm{O}_3^{2-}$ from +2 to +6 (more change) $\mathrm{I}_2$ oxidises S of $\mathrm{S}_2 \mathrm{O}_3^{2-}$ from +2 to +2.5 (less change)\ Thus $\mathrm{Br}_2$ is strong oxidant than $\mathrm{I}_2$