`3.92 g` of ferrous ammonium sulphate crystals are dissolved in `100 ml` of water, `20 ml` of this solution requires `18 ml` of `KMnO_(4)` during titration for complete oxidation. The weight of `KMnO_(4)` present in one litre of the solution is

Options

A. 34.76 g
B. 12.38 g
C. 1.23 g
D. 3.476 g

Answer

d

Explanation

The redox reaction involving the oxidation of `Fe^(2+)` is
`MnO_(4)^(-)+5Fe^(2+)+8H^(+)rarr5Fe^(3+)+Mn^(2+)+4H_(2)O`
Mol wt of ferrous ammonium suphate
`(NH_(4))SO_(4)FeSO_(4)6H_(23)O=392`
applyinhg molarity equation
`=(M_(2)V_(2))/(n_(2))`
or `(0.1xx20)/(5)=(M_(2)xx18)/(1)`
or `M_(2)=(0.1xx20)/(5xx18)=(M)/(45)`
Amount of `KMnO_(4)` present in one litre
=Molarity x mol wt
`1/45xx158=3.51` g
since 3.476 g is close to 3.51 g therefore option (d) is correct