Write complete chemical equation for :
(i) Oxidation of `Fe^(2+)"by" Cr_(2)O_(7)^(2-)` in acid medium
(ii) Oxidation of `S_(2)O_(3)^(2-) "by" MnO_(4)^(-)` in neutral aqueous medium

Explanation

(i)Acidified potassium dichromate oxidses iorn (II) salt to iron (III)
`Cr_(2)O_(7)^(2)+14H^(+)+6Fe^(2+)rarr2Cr^(3+)+6Fe^(3+)+7H_(2)O`
(ii) In neutral acqueolus median thisulphate is oxidised almost quantitatively to sulphate
`8MnO_(4)^(-)+3S_(2)O_(3)^(2)+H_(2)rarr8MnO_(2)+6SO_(4)^(2-)+2OH^(-)`