A sample of hydrazine sulphate `(N_(2)H_(6)SO_(4))` was dissolved in `100 mL` water. `10 mL` of this solution was reacted with excess of `FeCl_(3)` solution and warmed to complete the reaction. Ferrous ions formed were estimated and it required `20 mL` of `M//50 KMnO_(4)` solutions. Estimate the amount of hudrazine sulphate in one litre of solution.
Given `4Fe^(3+)+N_(2)H_(4)rarrN_(2)+4Fe^(2+)+4H^(+)`
`MnO_(4)^(-)+5Fe^(2+)+8H^(+)rarrMn^(2+)+5Fe^(3+)+4H_(2)O`

Explanation

The redox changes are:
`{:("For" FeCl_(3)",",e+Fe^(3+)rarrFe^(2+),,,),("For" N_(2)H_(6)SO_(4)",",N_(2)^(2-)rarr N_(2)^(o)+4e,,,),("For" KMnO_(4)",",5e+Mn^(7+)rarrMn^(2+),,,):}`
Meq.of `N_(2)H_(6)SO_(4)` in `10 mL "solution " = "Meq.of" KMnO_(4)`
`therefore (w)/(M//4)xx1000=2`
`( :. M.wt."of" N_(2)H_(6)SO_(4)=130)`
`:. w=(2xx130)/(4000)=0.065`
`:.` Wt.of `N_(2)H_(6)SO_(4)` in `10 mL=0.065 g`
Wt.of `N_(2)H_(6)SO_(4)` in `1000mL=6.5 "litre"^(-1)`