Question

0.31 gm of an alloy Fe+ Cu was dissolved in excess dilute H₂SO₄ and the solution was made up to 100 ml . 20 ml of this solution required 3 ml of N/30K-2Cr₂O₇ solution for exact oxidation. The % purity (in closest value) of Fe in wire is ____________.

Answer 1

The student's question involves calculating the percentage purity of iron in an alloy using stoichiometry based on a redox titration with potassium dichromate. Determining the moles of dichromate used allows for the calculation of moles, mass, and ultimately the percentage of iron in the original alloy sample.

Step-by-step explanation:

The question involves a titration procedure to determine the percentage purity of iron (Fe) in an alloy using potassium dichromate (K2Cr2O7) as the titrating agent in an acidic medium. The titration is based on the redox reaction where iron (II) ions are oxidized to iron (III) by dichromate ions. Using stoichiometry of the redox reaction and the normality of the potassium dichromate solution, we can calculate the amount of iron in the original sample and hence the percentage purity.

During the titration, each mole of K2Cr2O7 reacts with six moles of Fe2+ because the dichromate ion (Cr2O72-) requires six electrons to reduce to two chromium(III) ions (Cr3+), while Fe2+ donates one electron to form Fe3+.

Since 20 ml of the iron solution required 3 ml of N/30 potassium dichromate solution, we can calculate the moles of K2Cr2O7 and hence find the moles of iron that reacted. From the moles of iron, the mass and eventually the percentage purity are obtained. This percentage purity represents the amount of iron in the original 0.31 g sample of the alloy.