The empirical formaul represents the simplest formula for a compound.
Concept: Empirical Formula vs. Molecular Formula3m
Example: What is the empirical formula of dimethylhydrazine, C2H8N2, a colorless liquid used as a rocket fuel?1m
The empirical formula represents the lowest ratio of moles of each element within the compound.
Example: 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?5m
Whenever you are given the mass or percentages of elements you can assume it is out of 100 grams.
Example: 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.7m
Combustion analysis is a technique where an organic compound is combusted (exploded!!!) and the products are quantitatively measured.
Concept: Understanding Combustion Analysis2m
In a combustion reaction the organic compound is combusted to form carbon dioxide and water as products.
Example: A 0.2500 g sample contains carbon, hydrogen and oxygen and undergoes complete combustion to produce 0.3664 g of CO2 and 0.1500 g of H2O. What is the empirical formula of the compound?12m