Thiosulphate reacts differently with iodine and bromine in the reaction given below
`2S_(2)O_(3)^(2-) to S_(4)O_(6)^(2-)+2I^(-)`
`S_(2)O_(3)^(2-)+2Br_(2)+5H_(2)Oto2SO_(4)^(2-)+2Br^(-)+10H^(+)`
Which of the following statements justifies the above dual behaviour of thiosulphate?

Options

A. Bromine is a stronger oxidant than iodine
B. Bromine is a weaker oxidant than iodine
C. Thiosulphate undergoes oxidation by bromine and reduction by iodine in these reactions
D. Bromine undergoes oxidation and iodine undergoes reduction in these reactions

Answer

A

Explanation

`2overset(+2)(S_2)O_(3)^(-2^-2)(aq)+I_(0)^(0)(s) rarrS_(4)^(2.5)O_(6)^(2-)(aq)+2I^(-)(aq)`
`overset(+2)(S_2)O_(3)^(-2^-2)(aq)+2Br_(2)^(0)(l)+5H_2O(l)rarr2overset(+6)SO_(4)^(2-^(-2))(aq)+4Br^(-)(aq)+10H^(+)(aq)`
Bromine being stronger oxidising agent than `I_2`
oxidises S of `S_(2)O_(3)^(2-) ` to `SO_4^(2-)` whereas `I_2` oxidises it only into `S_(4)O_(6)^(2-)` ion.