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

Options

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

Answer

B

Explanation

The ionic equation for the reaction is :
`2MnO_(4)^(-)+6H^(+)+5SO_(3)^(2-)rarr2Mn^(2+)+5SO_(4)^(2-)+3H_(2)O`
5 mole of `SO_(3)^(2-)` ions are oxidised by `MnO_(4)^(-)` ions = 2 mol
1 mole of `SO_(3)^(2-)` ions is oxidised by `MnO_(4)^(-)` ions = 2/5 mol.