Sample Calculation:

An unknown solid contains 1.76 g of Aluminum and 1.57 g of Oxygen.

   1.76 g Al        = 0.0652 mol Al

29.68 g/mol Al

    1.57 g O    = 0.0981 mol O

16.00 g/mol O

Molar Ratio Between Aluminum and Oxygen:

(0.0652 mol Al) : (0.0981 mol O)  = 1.00 mol Al : 1.50 mol O

(0.0652 mol Al)   (0.0652 mol Al)

                                                 = 2.00 mol Al : 3.00 mol O

Empirical Formula:

Al2O3