Question

A sample $(5.6 \,g )$ containing iron is completely dissolved in cold dilute $HCl$ to prepare a $250\, mL$ of solution. Titration of $25.0 \,mL$ of this solution requires $12.5\, mL$ of $0.03 \,M \,KMnO _{4}$ solution to reach the end point. Number of moles of $Fe ^{2+}$ present in $250\, mL$ solution is $x \times 10^{-2}$ (consider complete dissolution of $FeCl _{2}$ ). The amount of iron present in the sample is $y \%$ by weight.
(Assume: $KMnO _{4}$ reacts only with $Fe ^{2+}$ in the solution
Use: Molar mass of iron as $56 \,g \,mol ^{-1}$ )
The value of $x$ is _______.

Answer 1

meq of $Fe ^{+2}=$ meq of $KMnO _{4}$
$x \times 10^{-2} \times 1000 \times 1=12.5 \times 0.03 \times 5 \times 10$
$x =1.875 \,mole$