A compound contains 28.9% sodium, 7.53% carbon and 30.2% oxygen. Calculate its empirical formula.

Question

A compound contains 28.9% sodium, 7.53% carbon and 30.2% oxygen. Calculate its empirical formula.

Answer 1

Let's assume we have 100 g of the unknown. This way, we can convert % to grams.

28.9 g Na x 1 mol Na / 23.0 g = 1.26 mols Na

7.53 g C x 1 mol C / 12 g = 0.628 mols C

30.2 g O x 1 mol O / 16 g = 1.89 mols O

Divide all by 0.628 in an effort to get whole numbers:

1.26 / 0.628 = 2.0 mols Na

0.628 / 0.628 = 1.0 mols C

1.89 / 0.628 = 3.0 mols O

Empirical formula = Na₂CO₃ (sodium carbonate)