The molecular formulaChemical formula showing the actual number of atoms of each element in a molecule. of an alkane shows the number of carbon and hydrogen atoms in each molecule. It shows the ratio of carbon atoms (C) to hydrogen atoms (H).
For example the formula of ethane is C2H6. The ratio of C:H atoms is 2:6.
An empirical formulaThe simplest whole number ratio of the atoms of each element in a compound. shows the simplest whole number ratio of atoms of each element present in a substance.
The empirical formula of an alkane is based on the simplest ratio of carbon to hydrogen atoms:
the simplest form of the C:H ratio for ethane is 1:3
the empirical formula is CH3 (note that the 1 is not written)