MnO_4^(2-)undergones disproportionation reaction in acidic medium but MnO_4^(-)does not . Give reason .

MnO_4^(2-)undergones disproportionation reaction in acidic medium but

1.	MnO_4^(2-)undergones disproportionation reaction in acidic medium but MnO_4^(-)does not . Give reason .
Answer» Solution :In `MnO_4^(-)`. Mn is in the highest oxidation STATE (+7)Therefore , it cannot oxidised further and HENCE does not undergo disproportionate. However , in ` MnO_4^(2+)`is in + 6 oxidation state. Therefore , it can increase its O.N to+ 7 and decrease its O.N. to some LOWER value Thus, it undergones DISPROPORTIONATION as : `3MnO_4^(2+) +4H^(+)rarr2MnO_4^(-) +MnO_2+2H_2O` Here O.N. of Mn increases from +6 (in `MnO_4^(2-)` ) to +7 and decreases to +4 (in `MnO_2` )