Empirical formula is the simplest ratio of atoms or elements present in a compound. It is the simplest formula showing relative amounts of different constituent atoms, and obtainable from the percentage composition of various atoms. Molecular formula is based on the actual number of atoms. It is the same or a simple multiple of the empirical formula. Determination of molecular formula of a compound requires an unequivocal idea of the exact molecular weight in addition to elemental composition or empirical formula. For example ribose (C5H10O5), formaldehyde (CH2O) glucose (C6H12O6), and acetic acid (CH3CO2H) all have different molecular formulae, but these four compounds have the same empirical formula of CH2O.
Emperical formula is the simplest ratio of atoms found in a compound, while a molecular formula identifies the number and types of atoms in each molecule. For example ribose (C5H10O5), formaldehyde (CH2O) glucose (C6H12O6), and acetic (C2H4O2) have different molecular formulas, but these four compounds have the emperical formula of CH2O.