A molecular formula shows the actual number of atoms of each element present in a single molecule of a compound.
Key points:
- Unlike the empirical formula, which shows only the simplest ratio, the molecular formula gives the true composition of the molecule.
- It is always a whole-number multiple of the empirical formula.
- To find it, chemists often use experimental data such as the compound’s molar mass.
- The molecular formula provides more detailed information about the compound’s identity and properties.
Examples:
- Glucose has the molecular formula C₆H₁₂O₆. Its empirical formula is CH₂O.
- Hydrogen peroxide has the molecular formula H₂O₂. Its empirical formula is HO.
- Water has both empirical and molecular formula H₂O, since it cannot be simplified further.
In short: The molecular formula tells us the exact number of each type of atom in a molecule.