Two oxides of a metal contain 27.6% and 30% oxygen, respectively. If the formula of the first compound is M3O4, find the formula of the second compound.
In the case of the 1st oxide, Mass of oxygen = 27.6
Mass of metal = 100 - 27.6 = 72.4
In the case of the 2nd oxide, Mass of oxygen = 30
Mass of metal = 100 - 30 = 70
Formula of the 1st oxide is M3O4
Number of atoms of metal in the 2nd oxide = (3/72.4) x 70
Number of atoms of oxygen in the 2nd oxide = (4/27.6) x 30
Ratio of metal : oxygen in the 2nd oxide = 2.9 : 4.35 or ≈ 2 : 3
The Formula of the 2nd oxide is M2O3.