Example

The molar mass of a compound containing only carbon and hydrogen has a molar mass of 114.0 g/mole. Further analysis determined the empirical formula of the compound to be C4H9. What is the molecular formula for this compound?

Step 1: Determine the number of empirical formula units in the compound.

Given: molar mass = 114.0 g/mole
Calculate: mass of empirical formula C4H9 = 57.0 g/mole




Step 2: Determine the molecular formula.

(Empirical formula)
x
(Number of empirical formula units)
 = Molecular formula
C4H9
x
2
= C8H18

The molecular formula is C8H18