Which of the following is a redox reaction ?

Options

A. `2CuSO_(4)+4KI rarr Cu_(2)I_(2)+2K_(2)SO_(4)+I_(2)`
B. `SO_(2)+H_(2)O rarr H_(2)SO_(3)`
C. `Na_(2)SO_(4)+BaCl_(2) rarr BaSO_(4)+2NaCl`
D. `CuSO_(4)+4NH_(3) rarr [Cu(NH_(3))_(4)]SO_(4)`

Answer

A

Explanation

O.N of Cu decreass from +2 in `CuSO_(4)` to +1 in `Cu_(2)I_(2)` while that of iodine increases from -1 in KI to 0 to `I_(2)`
`:.` reaction (A) is a redox reaction.