Formula masses and percent composition
of three theoretical compounds of Mg and O
Empirical Formula Example 2
2nd Step:  Formula Masses and their Percent Composition.
Mg = 24.31 g/mole
O = 15.999 g/mole
24.8
75.2
64.619
2(24.31) + 15.999 =
Mg2O
56.8
43.2
56.308
24.31 + 2(15.999) =
MgO2
39.7
60.3
40.309
24.31+15.999 =
**MgO
%O
%Mg
 
Formula Weight
Formula of Oxide MgxOy
Mg = 60.3%andO = 39.7%