Empirical and Molecular Formulae
Use this landing page to move quickly between the key empirical and molecular formulae revision pages for this section. Each card links to a focused page covering the simplest whole-number ratio of atoms and how to use molar mass to find the actual molecular formula.
Choose an Empirical and Molecular Formulae Page
Empirical and molecular formulae connect experimental composition data with the actual formula of a compound. These pages build from finding the simplest whole-number ratio of atoms through to using relative molecular mass to scale up to the true molecular formula.
Key idea: The empirical formula gives the simplest whole-number ratio of atoms in a compound, while the molecular formula gives the actual number of each type of atom in one molecule.
Empirical Formulae
Revise how to convert masses, percentages or combustion data into mole ratios and then into the simplest whole-number formula.
Start revisingMolecular Formulae
Learn how the empirical formula mass and relative molecular mass are used to find the molecular formula of a compound.
Start revisingHow to Use These Pages
Start with empirical formulae so that you can confidently convert composition data into a ratio of moles. Then move to molecular formulae, where the empirical formula is treated as a repeat unit and scaled using the relative molecular mass.
Exam focus: In empirical formula calculations, divide each amount in moles by the smallest value before converting to whole numbers. In molecular formula calculations, compare the relative molecular mass with the empirical formula mass.
Copyright notice: This revision page, including its written explanations, layout and teaching sequence, is produced for Online Learning System by Dr. Mohammed Al-Fatah. It is intended for student revision and may not be copied, redistributed or republished without permission.
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