The percentage composition of a compound may be obtained from the molecular formula of the compound. This is done as follows:
(i) Write down the molecular formula of the compound.
(ii) Calculate the mass of each element present in the molecule of the substance by multiplying the atomic mass of that element by the number of atoms in the molecule.
(iii) Calculate the molecular mass of the compound by adding the mass of all the atoms present in its molecules.
(iv) Calculate the mass percentage of each element by using the relationship.
Mass percentage of an element
= {Mass of the element in one molecule of the compound}/{Molecular mass of the compound} x 100
