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

Options

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

Answer

1

Explanation

`underset(=+7)underset(O.N of Mn)(MnO_(4)^(-))rarr underset(=+2)underset(O.N. of Mn)(Mn^(2+)) ("acidic soln")`
Since `ON` of `Mn` changes by 5 units, we conclude that 1 mol of `KMnO_(4)` provides 5 equivalents of `KMnO_(4)`.

Since the `ON` of `S` charges by 2 units, we can conclude that one mole of sulphite ion contains 2 equivalents of sulphite ion. Therefore, according to the law of equivalence we need 2 equivalents of `KMnO_(4)` to react with one mole of sulphite ion in acidic solution.
`5 Eqs KMnO_(4) -= 1 mol KMnO_(4)`
`1 Eq KMnO_(4) -= 1/5 mol KMnO_(4)`
`2 Eqs KMnO_(4) -= 2/5 mol KMnO_(4)`