A 2.80-g sample of haematite ore containing Fe3+ ions was dissolved in a concentrated acid and the solution was diluted to 250 mL. A 25.0 mL aliquot was reduced with Sn2+ to form a solution of Fe2+ ions. This solution of Fe2+ ions required26.4mL of a 0.0200 M K2Cr2O7 solution for complete oxidation back to Fe3+ ions. In the process Cr2O72- ions were converted to Cr3+.
masses, g/mol: Fe = 55.85 ; Fe2O3 = 159.7)
Calculate the percentage of Fe2O3 in the ore. (Molar
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