Determination of
molecular formula
•Can only obtain empirical formula from just the percents by mass.
•In order to get the molecular formula, the molar mass of the compound must be given. For cumene, the molar mass of cumene is 120.2 g/mol.
(from the problem)
•Determine the empirical formula weight. Divide this formula weight into the molar mass, you should get very close to a whole number.
•Multiply the empirical formula by this whole number to get the molecular formula.