Pearson Edexcel International GCSE Chemistry · specification 4CH1 · Paper 2 | Whole paper: All content including bold C statements · Free · no account needed
1(e) Chemical formulae, equations and calculations (4CH1 specification)
The quantitative core of the course: moles, masses, concentrations, gas volumes, yields — the part most learners avoid and most marks depend on.
Learn it on Incandio
The 8 Incandio pages that teach this — each explained in full, then proved in marked questions, taught back to an AI pupil and defended in a debate. Completely free.
- The Mole — Chemists have to count atoms and can only weigh them. The mole is the one idea that turns a mass on a balance into a number of particles.
- Reacting Masses and Percentage Yield — How much product a reaction should give, how much it actually gives, and why the two are never the same.
- Empirical and Molecular Formulae — Working out a formula you were never told, from nothing but the masses on a balance.
- Concentration and Gas Volumes — Counting particles in a solution you can only measure by volume, and in a gas you cannot weigh at all.
- Ionic Bonding — Why atoms give electrons away or take them, how far you can predict that from the periodic table, and how to draw it.
- Ionic Structures and Their Properties — Why salt melts at 800 °C, why it will not conduct until it does, and why both facts come from the same lattice.
- Covalent Bonding — What two atoms do when neither can afford to give an electron away.
- Simple Molecular Substances — Strong bonds inside, feeble forces outside — and why that makes methane a gas.
The teaching route this belongs to: Topic 1 · Principles of chemistry (Chemistry) — the lessons in order, with every gate.
Specification coverage
Topic 1 Principles of chemistry (e) Chemical formulae, equations and calculations — statements 1.27–1.48C (includes bold C statements assessed on Paper 2 only)
Assessment objectives: AO1, AO2. Suggested learning time: 140 minutes.
Required knowledge
- Writing formulae for compounds from ion charges
- Writing and balancing chemical equations, including state symbols
- Relative formula mass
- The mole, and the relationship between moles, mass and relative formula mass
- Calculating reacting masses from a balanced equation
- Concentration in g/dm³ and mol/dm³
- Bold C statements: percentage yield, empirical and molecular formulae, and the molar volume of a gas
Required skills
- Balance any equation reliably
- Convert between mass, moles and number of particles
- Work reacting-mass problems using the mole ratio from a balanced equation
- Calculate percentage yield and empirical formula (Paper 2)
How it is examined
- Multiple-choice and short-answer recall
- Application of the content to an unfamiliar context
- Extended open-response, marked on the quality of a connected explanation
Common mistakes
- Skipping the balanced equation and assuming a 1:1 ratio.
- Using volume in cm³ with a concentration in mol/dm³ without dividing by 1000.
- Rounding moles to one significant figure mid-calculation and carrying the error through.
- Giving a percentage yield above 100%, which always means the theoretical yield was calculated wrongly.
This page maps the specification. The pages above teach it, and the Chemistry lessons hold the whole course — completely free.