Moles (HT only) — AQA GCSE Chemistry
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Moles (HT only) explained
The mole is the unit used to measure chemical amount.
Read the full explanation
Its symbol is mol. One mole contains the Avogadro number of particles, 6.02 × 10²³, where the particles may be atoms, molecules, ions or electrons. The mass of one mole of a substance is its molar mass, found by adding the relative atomic masses in the formula and expressed in g/mol. For example, the molar mass of water, H₂O, is 18 g/mol, so 36 g of water is 2 mol. The relationship amount in moles equals mass divided by molar mass allows you to convert between mass and chemical amount. Always write mol after the number, for example 2 mol, not 2 m.
Your focus
- State the unit and symbol for chemical amount.
- Describe the number of particles in one mole.
- Calculate the amount in moles from mass and molar mass.
Moles (HT only) exam tips
Marking Points
- State that the mole is the unit of chemical amount and its symbol is mol.
- State that one mole contains 6.02 × 10²³ particles.
- Calculate molar mass by adding relative atomic masses from the formula.
- Use the relationship amount in moles equals mass divided by molar mass.
- Give the unit mol with any calculated chemical amount.
Examiner Tips
- 💡Write mol after every amount to secure the unit mark.
- 💡Show the molar mass calculation before substituting into the moles equation.
- 💡Check that mass is in grams and molar mass is in g/mol before dividing.
Common Mistakes
- Writing m as the symbol for mole; correct this by writing mol.
- Using relative atomic mass as a mass in grams without converting to molar mass; correct this by expressing molar mass in g/mol.
- Forgetting to state the type of particle when using the Avogadro number; correct this by naming the particles, such as atoms or molecules.