Hydrogen peroxide solution `(20 mL)` reacts quantitatively with a solution of `KMnO_(4) (20 mL)` acidified with dilute of `H_(2)SO_(4)`. The same volume of the `KMnO_(4)` solution is just decolourised by `10 mL` of `MnSO_(4)` in neutral medium simultaneously forming a dark brown precipitate of hydrated `MnO_2`. The brown precipitate is dissolved in `10 mL` of `0.2 M` sodium oxalate under boiling condition in the presence of dilute `H_(2)SO_(4)`. Write the balanced equations involved in the reactions and calculate the molarity of `H_(2)O_(2)`.

Explanation

Meq of oxalate `= 10 xx 0.2 xx 2 = 4`
Meq.of `MnO_(2)` formed = Meq. of oxalate `=4`
Meq of `KMnO_(4)` in `20 mL = 4`
`rArr` Normality of `H_(2)O_(2) xx 20 = 4`
`rArr` Normality of `H_(2)O_(2) = 0.20 N`
`rArr` Molarity of `H_(2)O_(2) = (0.20)/(2) = 0.10 M`
The balanced reactions are
`2KMnO_(4) + 5H_(2)O_(2) + 3H_(2)SO_(4) rarr 2MnSO_(4) + 5O_(2) + K_(2)SO_(4) + 8H_(2)O`
`MnO_(2) + Na_(2)C_(2)O + 2H_(2)SO_(4) rarr MnSO_(4) + Na_(2)SO_(4) + 2CO_(2) + 2H_(2)O`