The empirical formula represents the simplest formula for a compound.
Concept #1: Empirical Formula vs. Molecular Formula
Example #1: What is the empirical formula of dimethylhydrazine, C2H8N2, a colorless liquid used as a rocket fuel?
The empirical formula represents the lowest ratio of moles of each element within the compound.
Example #2: Elemental analysis of a sample of an ionic compound showed 2.82 g of Na, 4.35 g of Cl, and 7.83 g of O. What is the empirical formula and name of the compound?
Whenever you are given the mass or percentages of elements you can assume it is out of 100 grams.
Example #3: After a workout session, lactic acid (M = 90.08 g/mol) forms in muscle tissue and is responsible for muscle soreness. Elemental analysis shows that this compound contains 40% C, 6.7% H and 53.3% O. Determine the molecular formula.