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`

Answer

`(6.5gL^(-1))`

Explanation

Meq of `MnO_(4)^(-)` required `= 20 xx (1)/(50) xx 5 = 2`
`rArr` Meq of `Fe^(2+)` present in solution `= 2`
`rArr` millimol of `Fe^(2+)` present in solution `= 2` (n-factor `=1`)
Also,
`because` 4 millimol of `Fe^(2+)` are formed from 1 millimol `N_(2)H_(4)`
`because` 2 millimol `Fe^(2+)` from `(1)/(4) xx 2 = (1)/(2)` millimol `N_(2)H_(4)`
Therefore, molarity of hydrogen sulphate solution
`= (1)/(2) xx (1)/(10) = (1)/(20)`
`rArr` In `1 L` solution `(1)/(20)` mol `N_(2)H_(6)SO_(4)` is present.
`rArr` Amount of `N_(2)H_(6)SO_(4) = (1)/(20) xx 130 = 6.5 gL^(-1)`