Question -
Answer -
Mass percent of iron (Fe) = 69.9% (Given)
Masspercent of oxygen (O) = 30.1% (Given)
Number of moles of iron present in the oxide 
= 1.25
Number of moles of oxygenpresent in the oxide 
= 1.88
Ratio ofiron to oxygen in the oxide,
= 1 : 1.5
= 2 : 3
Theempirical formula of the oxide is Fe2O3.
Empirical formula mass of Fe2O3 = [2(55.85) + 3(16.00)] g
Molar mass of Fe2O3 = 159.69 g
Molecular formula of a compound is obtainedby multiplying the empirical formula with n.
Thus, the empirical formula of the givenoxide is Fe2O3 and n is 1.
Hence, the molecular formula of the oxide isFe2O3.