When `KMnO_(4)` solution is added to oxalic acid solution , the decolourisation is slow in the beginning but becomes instantaneous after some time because

Options

A. `CO_(2)` is formed as the product
B. reaction is exothermic
C. `MnO_(4)^(-)` catalyses the reaction
D. `Mn^(2+)` acts as autocatalyst

Answer

D

Explanation

When `KMnO_(4)` solution is added to oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after some time because `Mn^(2+)` acts as autocatalyst.
Reduction half `MnO_(4)^(-)+8H^(+)+5e^(-)rarrMn^(2+)+4H_(2)O]xx2`
Oxidation half `" "C_(2)O_(4)^(2-)rarr2CO_(2)+2e^(-)]xx5`
Overall equation
`" "2MnO_(4)^(-)+16H^(+)+5C_(2)O_(4)^(2-)rarr2Mn^(2+)+10 CO_(2) + 8H_(2)O`
End point of this reaction Colourless to light pink.