In presence of `H_(2)SO_(4)`25mL of 0.1 M `K_(2)Cr_(2)O_(7)` solution is required to oxiside`Fe^(2+)`ions in 25mL. Of a solution of ferrous salt. Estimate the amount of iron present per lite of the solution of ferrous salt.

Explanation

In acid medium ,`K_(2)Cr_(2)O_(7)`oxidises `Fe^(2+)`ions and itself gets reduced to `Cr^(3+)` ion.
Reaction :
`Cr_(2)O_(7)^(2-)+7Fe^(2+)+14^(+)to2Cr^(3+)+6Fe^(3+)+7H_(2)O`
So, 1mol of `K_(2)Cr_(2)O_(7)`-=6molof `Fe^(2+)`ions
or,1000mL. of 1M`K_(2)Cr_(2)O_(7)`solution -=6mol of `Fe^(2+)`ions.
or 1000mL of 1 M `K_(2)Cr_(2)O_(7)`solution `=6xx10^(-3)` mol of `Fe^(2+)`ions
or, 25mL of 0.1 M `K_(2)Cr_(2)O_(7)` solution
`=6xx10^(-3)xx25xx0.1`mol of `Fe^(2+)`ions
`=6xx10^(-3)xx25xx0.1xx55.85g of Fe^(3+)`ions
=0.3777g of `Fe^(3+)`[Atomic mass of Fe of =55.85g]
Therefore ,25mL,of the solution of ferrous salt contains 0.8377g of iorn .
`therefore`1L of this solution contains `(0.8377xx1000)/(25)`
=33.508 of Fe