Empirical, Molecular and Structural Formalae

The utility of the mole concept is further illustrated by the
problems of determining the empirical and molecular formulae of
the compounds. Empirical formula represents the simplest set of
whole numbers expressing the relative numbers of atoms in the
compound and anything that can be said about relative numbers of
atoms may be said about the relative numbers of moles of atoms. A
calculation of the relative numbers of moles of each element in
the compound will, therefore, lead us to the empirical formula of
the compound. The empirical formula implies nothing about how
many moles of atoms are actually in one mole of the compound.In fact, the molecular formula expresses the actual numbers of moles of atoms of each element present in one mole of the compound. The molecular formula weight is the whole number multiple of the empirical formula weight for a given compound.Molecular formula weight/Empirical formula weight = n(say)Thus if X represents the empirical formula of a compound, its molecular formula will be represented as (X)n.