Question

A $1.0g$ sample of $F{e}_2{O}_3$ solid of $55.2\%$ purity is dissolved in acid and reduced by heating the solution with zinc dust. The resultant solution is cooled and made upto $100.0ml$. An aliquot of $25.0ml$ of this solution requires $17.0ml$ of $0.0167M$ solution of an oxidant for titration. Calculate the number of moles of electrons taken up by the oxidant in the reaction of the above titration.

Answer 1

The number of millimoles of $F{e}_2{O}_3=\frac{1\times 55.2}{100\times 159.7}=3.456$ millimoles

Out of $100$ mL of solution, only $25$ mL is used.

Hence, the number of millimoles of $F{e}_2{O}_3$ used $=\frac{3.456}{4}=0.2839$ millimoles

The number of millimoles of the oxidant used per mole of $Fe$ atoms $=\frac{0.864}{0.2839}=3$ millimoles

The number of millimoles of the oxidant used per mole of $F{e}_2{O}_3$ $=2\times 3=6$ millimoles