Which type of reaction `MnO_(4)^(2-)`show with acid , dilute -alkali or water.

Answer

It is unstable in acidic medium and disproportionates
`3MnO_(4)^(2-)+4H^(+) to MnO_(2)+2MnO_(4)^(-)+2H_(2)O`
`3MnO_(4)^(2-)+2H_(2)O to 2MnO_(4)^(-)+MnO_(2)+4OH^(-)`