Cambridge O Level Chemistry · Syllabus 5070 · Stoichiometry
Molecular formula
What is Molecular formula?
The molecular formula of a compound states the number and type of different atoms present in one molecule of that compound, for example C2H4 for ethene, which contains two carbon atoms and four hydrogen atoms per molecule.
This definition is part of the Stoichiometry chapter in Cambridge O Level Chemistry.
Questions students ask about Molecular formula
What is the difference between a molecular formula and an empirical formula?
The molecular formula gives the number and type of atoms in one molecule of a compound, for example \(\mathrm{C_6H_{12}O_6}\) for glucose. The empirical formula gives the simplest whole-number ratio of the different atoms or ions, so for glucose it is \(\mathrm{CH_2O}\). They describe the same substance but answer different questions. Simplify only when the numbers share a common factor: the empirical formula of \(\mathrm{CO_2}\) is still \(\mathrm{CO_2}\), because 1 : 2 is already the simplest ratio.