How are empirical and molecular formulas related?
The molecular formula is always a whole number multiple of the empirical formula.
The empirical formula is by definition the simplest whole number ratio defining constituent atoms in a species. The molecular formula is always a whole number ratio of the empirical formula.
Typically an organic compound would be combusted where its combustion products,
These data allow an empirical formula to be calculated. Given a molecular mass (by some other means), the molecular formula may be adduced.
So the take home message:
And of course