In the reactions given below, thiosulphate reacts differently with iodine than with bromine.



Which of the following statements best describes the above dual behaviour of thiosulphate?

1. Bromine is a stronger oxidant than iodine

2. Bromine is a weaker oxidant than iodine

3. Thiosulphate undergoes oxidation by bromine and reduction by iodine in these reactions

4. Bromine undergoes oxidation and iodine undergoes reduction in these reactions

Hint: Gain of electron is reduction and loss of electron is oxidation
The two reactions are as follows:
Element Change in oxidation state Reaction
S +2 ---> 2. 5 oxidation
I  0----> -1 reduction
S +2-----> +6 Oxidation
Br 0 ----> -1 reduction

In both the reactions, halogen acts as an oxidising agent and oxidised S2O32- and it self gets reduce. The change in oxidation state of sulphur in case of Br2 is more than in case of I2. Hence, Br2 being stronger oxidisng agent than I2