moles of Fe = 1.26/56 = 0.0225 moles of O2 = (1.8-1.26)/16 = 0.03375 so, for every atom of Fe there is 3/2 moles of O so, empirical formula is Fe2O3 Solution moles of Fe = 1.26/56 = 0.0225 moles of O2 = (1.8-1.26)/16 = 0.03375 so, for every atom of Fe there is 3/2 moles of O so, empirical formula is Fe2O3.