Cambridge IGCSE·Co-ordinated Sciences 0654·Chemistry
Stoichiometry
Key knowledge — Stoichiometry
Formulas & equations
Moles = mass (g) ÷ molar mass (g/mol)Moles = volume (dm³) × concentration (mol/dm³)Moles of gas at RTP = volume (dm³) ÷ 24 (at room temperature and pressure)% yield = (actual yield ÷ theoretical yield) × 100% purity = (mass of pure substance ÷ total mass) × 100Empirical formula: simplest whole-number ratio of atoms. Molecular formula: actual ratio.
Key facts & rules
- Avogadro's number: 1 mole contains 6.02 × 10²³ particles.
- Molar mass: sum of Ar values from the periodic table for one formula unit.
- Balancing equations: atoms must be equal on both sides — only coefficients can change, not formulae.
- Limiting reagent: the reactant that runs out first, determining the maximum yield.
- Excess reagent: the reactant that is not used up.
IGCSE Chemistry — Stoichiometry
638 Cambridge IGCSE 0654 chemistry past paper questions on stoichiometry, organised by subtopic. Pick a subtopic to start practising.
About stoichiometry on IGCSE 0654
Relative atomic mass, the mole, formulae, balanced equations and reacting-mass calculations.