Topic 3 of 12 · 4 modules planned

Stoichiometry

Formulae, equations and the mole: how chemists count particles by weighing them.

Modules

Module 1 · syllabus 3.1
Formulae and equations
How do you balance a reaction?
This module is planned. It will have readings, an experiment, practice with self-checks and a final check.

Syllabus statements for this topic · for teachers · 19 statements

Core for every pupil · Supplement also for Extended entry. Paraphrased from the Cambridge IGCSE Chemistry 0620 syllabus (2026–2028); check the official syllabus for exact wording.

3.1 Formulae

3.1.1Formula recall across the required substance setC
3.1.2Molecular formula as atom inventoryC
3.1.3Formula from a particle modelC
3.1.4Word/symbol equations and physical statesC
3.1.5Empirical ratio versus molecular formulaS
3.1.6Ionic formula from charge balanceS
3.1.7Balanced ionic equations with state symbolsS
3.1.8Equation from unfamiliar reaction informationS

3.2 Relative masses of atoms and molecules

3.2.1Relative atomic mass and carbon-12 referenceC
3.2.2Relative molecular/formula massC
3.2.3Reacting masses using simple mass ratiosC

3.3 The mole and the Avogadro constant

3.3.1Mass and amount concentration unitsC
3.3.2Mole and Avogadro countS
3.3.3Mass, molar mass, moles and particle numberS
3.3.4Gas calculations at r.t.p.S
3.3.5Reaction amounts, limiting reagent, gas/solution volumes, concentrationS
3.3.6Titration amount/concentration calculationsS
3.3.7Empirical and molecular formula calculationsS
3.3.8Yield, mass composition and purityS