An iron ore sample contains Fe2O3 plus other impurities. A 752-g sample of impure iron ore is heated with excess carbon, producing 453 g of pure iron by the following reaction:
Fe2O3 (s) + 3 C (s) → 2 Fe (s) + 3 CO (g)
What is the mass percent of Fe 2O3 in the impure iron ore sample? Assume that Fe 2O3 is the only source of iron and that the reaction is 100% efficient.