What is empirical formula and how is it worked out?

This is the lowest/simplest ratio of the molecule. For example propene has the formula C₃H₆ - if we look a the subscript numbers _{(the ones down here!)} we can see that smaller numbers are possible. It is important to know the relationship between these numbers. In this case you can write this simply as C_nH_2n. Therefore the empirical formula for propene is CH₂.Another example is propane which is C₃H_8. We can work out that the relationship is as follows: C_nH_2n+2 and therefore the empirical formula is CH₄.