The number of moles of `KMnO_(4)` that will be needed to react with one mole of sulphite ion in acidic solution is

Options

A. `3/5`
B. `4/5`
C. `2/5`
D. 1

Answer

C

Explanation

`MnO_(4)^(-)+8H^(+)+5e^(-) rarrMn^(2+)+ 4H_2O " "....(i)`
(Reduction of `MnO_4^(-)` in acidic solution)
`SO_(3)^(2-) +H_2O rarr SO_(4)^(2-) +2H^(+) + 2e^(-) " "...(ii)`
(Oxidation of sulphite ion to sulphate ion)
Eq. (i) `xx2 +` Eq. (ii)`xx5` :
`2MnO_(4)^(-) + 5SO_(3)^(2-) +6H^(+) rarr 2Mn^(2+) +5SO_(4)^(2-) +3H_2O`
5 moles of sulphite ion needed = 2 moles of `MnO_(4)^(-)`
1 mole of sulphite ion needed = 2 / 5moles of `MnO_(4)^(-)`