Empirical Formula

The empirical formula is the simplest whole-number ratio of atoms of each element in a compound.For example, ethane has the molecular formula C₂H₆ and the empirical formula CH₃.To find the empirical formula from mass or percentage data: divide the mass or percentage of each element by its A_r, then divide each answer by the smallest value to get the ratio.Example: a hydrocarbon contains 82.8% carbon and 17.2% hydrogen. C: 82.8 / 12.0 = 6.90. H: 17.2 / 1.0 = 17.2. Dividing by 6.90 gives C 1 : H 2.5. Doubling gives C₂H₅.If the ratio is not a whole number, multiply every value by the same small number (for example 2 or 3) until they are all whole numbers.