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?
Select the correct option:
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
D
Bromine is a weaker oxidant than iodine
✓ Correct! Well done.
✗ Incorrect. Try again or view the solution.
Solution
In the reaction of $\mathrm{S}_2 \mathrm{O}_3{ }^{2-}$ with $\mathrm{I}_2$, oxidation state of sulphur changes to +2 to +2.5
In the reaction of $\mathrm{S}_2 \mathrm{O}_3{ }^{2-}$ with $\mathrm{Br}_2$, oxidation state of sulphur changes from +2 to +6 .
∴ Both $\mathrm{I}_2$ and $\mathrm{Br}_2$ are oxidant (oxidising agent) and $\mathrm{Br}_2$ is stronger oxidant than $\mathrm{I}_2$.
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