1.8 Determine the molecular formula of an oxide of iron, in which the mass percent of iron and oxygen are 69.9 and 30.1, respectively.
Mass percent of iron (Fe) = 69.9%
Mass percent of oxygen (O) = 30.1%
Number of moles of iron present in the oxide = = 1.25
A number of moles of oxygen present in the oxide = 30.1/16.0
= 1.88
Ratio of iron to oxygen in the oxide,
= 1.25:1.88
=
= 1 : 1.5
= 2 : 3
The empirical formula of the oxide is .
Empirical formula mass of Fe2O3 = 159.69 g
Molecular formula of a compound is obtained by multiplying the empirical formula with n.
Thus, the empirical formula of the given oxide is and n is 1.
Hence, the molecular formula of the oxide is .
