Casino_of_Envy

An ore containing magnetite, Fe3O4, was analysed by dissolving a 4.9 g sample in concentrated HCl, giving a mixture of Fe2 and Fe3 . After adding HNO3 to oxidize any Fe2 to Fe3 , the resulting solution was diluted with water and the Fe3 precipitated as Fe(OH)3 by adding NH3. After filtering and rinsing, the residue was ignited, giving 2.8 g of pure Fe2O3. Calculate the %w/w Fe3O4 in the sample (Fe3O4 =231.54 g/mol, Fe2O3 = 159.69 g/mol)