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What does a mole of a substance represent?
Avogadro's number (6.02 x 10^23) of particles of that substance A mole is a unit of mass equal to the relative molecular mass in grams of any substance
Quantitative Chemistry is a core part of GCSE Chemistry. Revise the key concepts and common mistakes below, then lock them in with the free games.
Key concepts Percentage composition Mass of an element ÷ Mr of compound × 100
Theoretical yield Mass of product predicted by the equation
Actual yield Mass of product actually obtained in the lab
Percentage yield Actual yield ÷ theoretical yield × 100
Atom economy Mr of useful products ÷ Mr of all reactants × 100
Sustainable reaction High yield and high atom economy — less waste
n = m / Mr Moles = mass in grams divided by relative formula mass
Mole ratio The ratio of moles from the balanced equation coefficients
Limiting reactant The reactant fully used up — it limits the product
Excess reactant A reactant left over after the reaction stops
Empirical formula Simplest whole-number ratio of atoms in a compound
Molecular formula Actual numbers of each atom in a molecule
Mole An amount of substance containing 6.02 × 10²³ particles
Avogadro constant 6.02 × 10²³ particles per mole
Show all 14 key concepts What your exam board covers Where Quantitative Chemistry sits in each exam board's specification. Tap a board to see what it lists.
AQA Quantitative chemistry Spec 8462 Chemical measurements, conservation of mass and the quantitative interpretation of chemical equations Use of amount of substance in relation to masses of pure substances Yield and atom economy of chemical reactions (chemistry only) Using concentrations of solutions in mol/dm³ (chemistry only) Use of amount of substance in relation to volumes of gases (chemistry only) Source: AQA GCSE Chemistry (8462) specification — Subject content , accessed 23 June 2026.
CCEA Quantitative chemistry Spec 1110 Part of: Unit 1 — Structures, trends, chemical reactions, quantitative chemistry and analysis
Source: CCEA GCSE Chemistry (2017) specification , accessed 9 July 2026.
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Common mistakes to avoid Questions where students often pick the tempting wrong answer — make sure you know the right one:
What does a mole of a substance represent? ✗ A mole is a unit of mass equal to the relative molecular mass in grams of any substance. ✓ Avogadro's number (6.02 x 10^23) of particles of that substance.
Why do industries care about atom economy? ✗ It makes reactions faster ✓ Higher atom economy means less waste and more sustainability
At room temperature and pressure, what volume does 1 mole of any gas occupy? ✗ Heavier gases occupy a smaller volume per mole because their particles are denser. ✓ Approximately 24 dm^3 (24,000 cm^3), regardless of the identity of the gas.
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