The purple colour of `KMnO_4`, will not be discharged by which of the following reagents? 1)M n S O 4 / Z n 2 + 2)H 2 O 2 / H + 3)K N O 3 4)K 2 S / H +

Options

A. `MnSO_4//Zn^(2+)`
B. `H_2 O_2// H^+`
C. `KNO_3`
D. `K_2S//H^+`

Answer

C

Explanation

`Mn^(2+)` (in presence of `Zn^(2+)`), `H_2O_2 " and " S^(2-)` are reducing agents and reduce `Mn^(2+)` by which colour is discharged. While in `KNO_3`, nitrogen is in +5 oxidation state and cannot be further oxidized and hence, cannot act as reducing agent.