Every
compound is represented by certain molecular formula or formula unit.
Determination of molecular formula or formula unit is based on percentage
composition of different elements in a given compound. According to the Law of Definite
Proportion, “compounds are made up of different elements in definite ratio”. On
the basis of chemical analysis, we can calculate percentage of each and every
element. An empirical formula is calculated with the help of the percentage
composition of elements in a compound.
Empirical Formula is defined as the simple ratio between constituent elements of compound.
For example, empirical formula
for Ethane (C2H6 – Molecular Formula) is CH3.
Empirical formula is determined by percentage composition in following manner
The
molecular formula is defined as exact ratio between constituent elements of the
compound. An empirical formula is converted into a molecular formula by
multiplication of factor n.
Molecular
Formula = Empirical Formula x n
Factor
n is defined as ratio between molecular weight and empirical weight.
The
molecular weight is calculated separately with the help of certain experimental
techniques or with the help of Vapour Density and empirical weight is
calculated with the help of empirical formula.
