How many percent of Fe is in Fe2O3 and Fe3O4. How to determine?

The iron content in oxides, (mass fraction), w is calculated by the formula:

w = n * Ar (Fe) * 100% / Mr (oxide), where;

w – Iron content;

n is the number of atoms of the element in the compound;

Ar (Fe) is the atomic mass of iron (56);

Mr (oxide) is the molecular weight of the oxide;

Mr (oxide) – is calculated by the formula:

Mr = n (Fe) * Ar (Fe) + n (O) * Ar (O), where Ar (O) is the atomic mass of oxygen (16);

1) Mr = 2 * 56 + 3 * 16 = 112 + 48 = 160;

w = 2 * 56 * 100/160 = 70%, mass fraction of iron.

2) Mr = 3 * 56 + 4 * 16 = 232;

w = 3 * 56 * 100/232 = 72.41%, mass fraction of iron.