Question

1. Magnetite is a mineral having the formula Fe₃O₄. A 1.1324 g sample of magnetite ore was dissolved in concentrated HCl to give a solution that contained a mixture of Fe²⁺ and Fe³⁺. Nitric acid was added and the solution was boiled for a few minutes, which converted all of the iron to Fe³⁺. The Fe³⁺ was then precipitated as Fe₂O₃×xH₂O by addition of NH₃. After filtration and washing, the residue was ignited at a high temperature to give 0.5394 g of pure Fe₂O₃. Calculate a) the percent Fe and b) the precent Fe₃O₄ in the sample.

Answer 1