Transition metals can act as catalysts because these can change their oxidation states. How does Fe(III) catalyse the reaction between iodide and persulphate ions ?

Explanation

Iodide ion reacts with persulphate ion (in presence of `Fe^(3+)`) according to equation :
`2I^(-)+S_(2)O_(8)^(2-)overset(Fe^(3+))rarr I_(2)+2SO_(4)^(2-)`
Role of `Fe^(3+)` ion : `2Fe^(3+)+2I^(-)rarr 2Fe^(2+)+I_(2)`
`2Fe^(2+)+S_(2)O_(8)^(2-)rarr 2Fe^(3+)+2SO_(4)^(2-)`