The empirical formula Empirical formula of a compound is the simplest, whole number ratio of atoms of each element in a compound. of a compound is the simplest, whole number ratio of atoms of each element in a compound.
The molecular formula Shows the actual number of atoms of each element present in a compound. shows the actual number of atoms of each element present in a compound.
Example:
Molecular formula
Empirical formula
C6H12
CH2
C6H6
CH
CH4
CH4
Molecular formula
C6H12
Empirical formula
CH2
Molecular formula
C6H6
Empirical formula
CH
Molecular formula
CH4
Empirical formula
CH4
Converting empirical formulae to molecular formulae
You can work out the molecular formula from the empirical formula, if you know the relative mass formula (Mr) of the compound.
Add up the atomic masses of the atoms in the empirical formula.
Example:
The empirical formula of a hydrocarbon is CH2 and its Mr is 42.
the mass of the atoms in the empirical formula is 14
42 Ă· 14 = 3
multiply the numbers in the empirical formula by 3