If `CO_(2)` is passed through a green aqueous solution of potassium manganate, the solution turns violet and gives a brown precipitate. Explain.

Explanation

`CO_(2)` is an acidic oxide. It supplies `H^(+)` ions in aqueous solution. Disproportionation of potassium manganate in acidic medium, gives a violet solution of potassium permanganate and a brown precipitate of `MnO_(2)`.
`CO_(2)+H_(2)O hArr H_(2)CO_(3)hArr 2H^(+)+CO_(3)^(2-)`
`overset(VI)(3Mn)O_(4)^(2-)+4H^(+)to overset(VII)(2Mn)O_(4)^(-)("violet")+overset(IV)(MnO_(2)darr)("brown")+2H_(2)O`