For example the formula of glucose is C6H12O6. The empirical formula is CH2O; this tells us that there is always 1 carbon for every 2 hydrogen atoms and one oxygen atom. This ratio between atoms applies on a molar level as well: for every one mole of carbon there are 2 moles of hydrogen and one mole of oxygen.

There are a few different types of empirical formula problems. 

1. You may be given percent compositions to determine the empirical formula

2. You may be given masses to determined the empirical formula

3. Combustion analysis

Determine the molecular formula:

1. Find the empirical formula: The empirical formula is the simplest ratio of atoms in the compound, found using experimental data.

2. Calculate the empirical formula mass: The empirical formula mass is the sum of the atomic masses of all the atoms in the empirical formula.

3. Determine the molecular formula mass: The molecular formula mass is the actual mass of one molecule of the compound, found using the molar mass.

4. Calculate the multiple: Divide the molecular formula mass by the empirical formula mass to find the multiple.

5. Multiply the empirical formula by the multiple: Multiply each subscript in the empirical formula by the multiple to obtain the molecular formula.