Percentage composition:
- The percentage composition of a compound is the percentage by weight of each element present in the compound.
- Quantitative determination of the constituent elements by suitable methods provides the percent elemental composition of a compound.
- If the percent total is not 100, the difference is considered as percent oxygen.
- From the percentage composition, the ratio of the atoms of the constituent elements in the molecule is calculated.
Empirical formula:
The simplest ratio of atoms of the constituent elements in a molecule is called the empirical formula of that compound. e.g. The empirical formula of benzene is CH
Molecular formula:
- Molecular formula of a compound is the formula which indicates the actual number of atoms of the constituent elements in a molecule.
e.g. The molecular formula of benzene is C6H6.
- It can be obtained from the experimentally determined values of percent elemental composition and molar mass of that compound.
- Molecular formula can be obtained from the empirical formula if the molar mass is known.
Molecular formula = r\(\times\) Empirical formula
\(r =
\frac{Molecular\ mass}{
Empirical\ for\ mulamass}\)
