Practical Organic Chemistry
6.0 Determination of Empirical Formula and Molecular Formula
6.0 Determination of Empirical Formula and Molecular Formula
Determination of Empirical Formula: The empirical formula of a molecule is determined using the % of elements present in it./ The following method is adopted.
| Element | % | Relative No. of atoms = % /at. wt. | Simplest Ratio | Empirical formula |
Relative No. of Atoms: Divide the percentage of each element present in a compound by its atomic weight. This gives the relative number of atoms of an element in the molecule.
Simplest Ratio: Find out the lowest value of a relative number of atoms and divide each value of a relative number of atoms by this value to get the simplest ratio of elements.
If the simplest ratio obtained is not complete integers, multiply them by a common factor to get integer values of simplest ratio.
Empirical Formula: Write all constituent atoms with their respective number of atoms derived in simplest ratio. This gives the empirical formula of the compound.
Molecular Formula: Molecular formula $ = n \times $empirical formula where $‘n’$ is the whole number of obtained by $$n = \frac{{{\text{molecular weight of compound}}}}{{{\text{empirical formula weight of compound}}}}$$
a molecular weight of the organic compound can be determined by any method for which data is given.
