Consider the reaction : 2s_(2)O_(3)^(2-)(aq)+I_(2)(s)rarrS_(4)O_(6)^(2-)(aq)+2I^(-)(aq)S_(2)O_(2)^(2-)(aq)+2Br_(2)(l)+5H_(2)O(l)rarr2SO_(4)^(2-)(aq)+4Br^(-)(aq)+10H^(+)(aq) Why does the same reducant thiosuphatereact differently with iodine and bromine?

Consider the reaction : 2s_(2)O_(3)^(2-)(aq)+I_(2)(s)rarrS_(4)O_(6)^(2

1.	Consider the reaction : 2s_(2)O_(3)^(2-)(aq)+I_(2)(s)rarrS_(4)O_(6)^(2-)(aq)+2I^(-)(aq)S_(2)O_(2)^(2-)(aq)+2Br_(2)(l)+5H_(2)O(l)rarr2SO_(4)^(2-)(aq)+4Br^(-)(aq)+10H^(+)(aq) Why does the same reducant thiosuphatereact differently with iodine and bromine?
Answer» Solution :The average O.N of S in `S_(2)O_(3)^(2-)`is +2 while in `S_(4)O_(6)^(2-)` it is +2.5 The O.N of S in `SO_(4)^(2-)` is +6 SINCE `Br_(2)` is a stronger oxidising agent that `I_(2)` it oxidises s of `S_(2)O_(3)^(2-)` to higher OXIDATION state of +6 and hence FORMS `SO_(4)^(2-)` ion `I_(2)` howevr being aweaker oxidising agentoxidises S of `S_(2)O_(3)^(2-)` ion to a loweroxidation of +2.5 in `S_(4)O_(6)^(2-)` ion it is because of this reason that thiosuplhate REACTS differently with `Br_(2)`and `I_(2)`