We already know the molar mass of C is 12.01g/mol, of H is 1.008 g/mol, and of O is 16g/mol.
If the molecular formula were also the empirical formula (which is CH2O), then it would have a molar mass of:
12.01g/mol +2*(1.008g/mol)+ 16g/mol= 30.03g/mol
However, the actual molar mass of the molecular formula is 60.g/mol, which is about twice as large as 30.03g/mol. Therefore, we have to multiply the empirical formula by 2.
The molecular formula of this compound is (2) C2H4O2.
Hope this would help~