Decolourisation of acidified permaganate in fast by Mohr's salt , but is solw by oxalate . Expalin .

Explanation

Oxalate, `.^(-)OOC-COO^(-)`, on oxidation gives `CO_(2)`. It is involves breaking of C-C bond, which requires energy.
Hence decolourisation of `MnO_(4)^(-)` by `C_(2)O_(4)^(2-)` is slow. On the other hard Mohr.s salt is a complex salt containing `Fe^(2+)` ions.