Magnetite is a binary compound containing only iron and oxygen. The percent, by weight, of iron is 72.360 %. What is the empirical formula of magnetite?

Fe3O4

Explanation:

We can deduce the empirical formula from the percentage compositions.

Since it contains only two atoms, the % composition of the oxygen is 100 - 72.36 = 27.64

Now, we divide each by the relative atomic masses of each. The relative atomic mass of iron is 56 and that of oxygen is 16.

Fe = 72.36/56 = 1.292

O = 27.64/16 = 1.7275

Now we divide by the smallest:

Fe = 1.292/1.292 = 1

O = 1.7275/1.292 = 1.33 = 4/3

The ratio is thus 1:1.33 or 1:4/3

Multiplying through by 3 will yield: 3:4

The empirical formula is thus Fe3O4