A sample (5.6 ~g) containing iron is completely dissolved in cold...

Moles of ${Fe}^{2 +}$ present in $250ml$ solution $= x \times {10}^{- 2}$

Moles of ${Fe}^{2 +}$ present in $25ml$ solution $= x \times {10}^{- 3}mole$

At equivalence point

eq. of ${Fe}^{2 +}$ = eq. of ${KMnO}_{4}$

\left(Moles\right){Fe}^{2 +} \times \left(vf\right){Fe}^{2 +} = {\left(Moles\right)}_{{KMnO}_{4}} \times {\left(vf\right)}_{{KMnO}_{4}}$</p><p>$x \times {10}^{- 3} \times 1 = 0 .03 \times 12 .5 \times {10}^{- 3} \times 5$</p><p>$x = 1 . 875mole$</p><p>Moles of${Fe}^{2 +}$present in$250ml$solution$= 1 . 875 \times {10}^{- 2}$</p><p>Mass of${Fe}^{2 +}$present in$250ml$solution</p><p>$= 1 . 875 \times {10}^{- 2} \times 56gm$</p><p>$= 1 . 05gm$</p><p>$Fe\left(y\right) = \dfrac{1 .05}{5 .6} \times 100$</p><p>$= 18 . 75 %