निम्नलिखित अभिक्रयाओं में ऑक्सीकरण तथा अपचायक को पहचानिए -
(i) `Cl_(2)(g)+2Br^(-)(Aq)to2Cl^(-)(aq)+Br_(2)(aq)`
(ii) `CH_(4)(g)+4Cl_(2)(g)toC Cl_(4)(g)+4HCl(g)`
(iii) `I_(2)(aq)+2S_(2)O_(3)^(2-)(aq)to2I^(-)(Aq)+S_(4)O_(6)^(2-)`
(iv) `2H^(+)(Aq)+MnO_(2)(s)+C_(2)H_(2)O_(4)(aq)toMn^(2+)(aq)+2CO_(2)(g)+2H_(2)O(l)`

Explanation

`KMnO_(4):K=+1,Mn=+7,O=-2,K_(2)Cr_(2)O_(7):K=+1`,
`Cr=6,O=-2,KClO_(4):=+1,Cl=+7,O=-2`