# Example 1 - Molecular Formula

The percentage composition of a compound is 92.26% C and 7.74% H. The relative molecular mass of the compound is 78. Determine its molecular formula of the compound

In order to find molecular formula of a chemical compound, we need to find the empirical formula of the compound before hand.

Finding the empirical formula:
 Element C H Percentage $92.26%$ $7.74%$ Mass in 100g $92.26g$ $7.74g$ Number of mole Simple ratio $1$ $1$

The empirical formula of the compound = CH

Finding the molecular formula

Let's say the molecular formula of the compound
= CnHn

where n is a round number.

The relative molecular mass of  CnHn
= n(12) + 4(1) = 78
13n = 78
n = 78/13 = 6

The molecular formula of the compound
C6H6