Two oxides of a metal contain 27.6% and 30.0% of Oxygen, respectively. If the formula of the first be M3O4. Find that of the second.
First oxide Second oxide
Oxygen = 27.6% Oxygen = 30.0%
Metal = 72.4% Metal = 70.0%
Formula = M3O4 Formula = ?
Let the atomic weight the metal be x.
Therefore, percentage by weight of the metal in the compound M3O4 = 3×x×1003x+64=72.4(given)
Hence, x = 55.97 = 56.
Thus, having known the atomic weights of the metal and oxygen, empirical formula of the second oxide can be worked out as under
Thus, the formula of the second oxide is M2O3.