Which of the following is a redox reaction?

Options

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

Answer

A

Explanation

Since Cl in `CrO^(-)` has an O.N. of +1 which is higher than the lowest O.N. of +5 and lower than the highest O.N. of +5, therefore, `CIO^(-)` can act as an oxidising as well as a reducing agent.