What are empirical formulas?
The empirical formula is the lowest term ratio of the atoms found in a molecule.
An example would be the empirical formula for a carbohydrate is
one carbon for two hydrogens for one oxygen
The carbohydrate glucose has a formula of
Notice that the ratio is 1 C to 2 H to 1 O.
For the alkane group of hydrocarbons the molecular formulas are
In each of these molecules the molecular formula can be determines from a base formula of
This is the empirical formula for all alkanes.
Here is a video which discusses how to calculate an empirical formula.
video from: Noel Pauller
I hope this was helpful.