Thiosulphate reacts differently with iodine and bromine in the reaction given below : 2S2O^2- 3 + I2 → S4O^2- 6 + 2I^-

Question

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

\(2S_2 O ^{2-}_3 + I_2 \rightarrow S_4 O ^{2-}_6 + 2I ^-\)

\(S_2 O^{2-}_3 + 5 Br_2 + 5H_2O \rightarrow 2SO ^{2-}_4 + 4Br ^- + 10 H ^+\)

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

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

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

(3) Bromine is a stronger oxidant than iodine 

(4) Bromine is a weaker oxidant than iodine

Answer 1

Correct option is (3) Bromine is a stronger oxidant than iodine 

In the reaction of \(S_2 O_3 {^{2-}}\) with \(I_2,\) oxidation state of sulphur changes to +2 to +2.5

In the reaction of \(S_2 O_3 {^{2-}}\) with \(Br _2 ,\) oxidation state of sulphur changes from +2 to +6.

\(\therefore \) Both \(I_2\) and \(Br_2\) are oxidant (oxidising agent) and \(Br_2 \) is stronger oxidant then \(I_2.\)