Give reason: The brown colour of an acidified dilute solution of iodine in aqueous potassium iodide is intensified by addition of sulphite.

Explanation

Nitrite ion being stronger oxidising agent than iodine ion, oxideses `I^(Theta) to I_(2)` and itself gets reduced to `NO`. Thus the brown colour is intensified.
`NO_(2)^(Theta) + 2I^(Theta)+4H^(o+) to 2NO+I_(2)+2H_(2)O`
Whereas sulphite is weaker oxidising agent than iodide and hence `I_(2)` is reduced to `I^(Theta)` and the solution becomes colourless or the brown colour is discharged.
`I_(2)+SO_(3)^(2-)+H_(2)O to SO_(4)^(2-)+2H^(o+)+2I^(Theta)`.