Pearson Edexcel International GCSE Chemistry · specification 4CH1 · Paper 2 | Whole paper: All content including bold C statements · Free · no account needed
3(c) Reversible reactions and equilibria (4CH1 specification)
Reactions that go both ways, dynamic equilibrium, and predicting which way a change pushes them.
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The Incandio page that teaches this — each explained in full, then proved in marked questions, taught back to an AI pupil and defended in a debate. Completely free.
- Dynamic Equilibrium — Nothing appears to be happening, everything is still happening — and that is what lets conditions shift it.
The teaching route this belongs to: Topic 3 · Physical chemistry (Chemistry) — the lessons in order, with every gate.
Specification coverage
Topic 3 Physical chemistry (c) Reversible reactions and equilibria — statements 3.21–3.28C (includes bold C statements assessed on Paper 2 only)
Assessment objectives: AO1, AO2. Suggested learning time: 70 minutes.
Required knowledge
- Reversible reactions and the meaning of dynamic equilibrium
- The effect of changing temperature, pressure and concentration on the position of equilibrium
- The Haber process: conditions used and the reasons for the compromise
- Bold C statements: the contact process and further equilibrium applications
Required skills
- Predict the direction of shift for a given change
- Explain why industrial conditions are a compromise between yield and rate
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
- Describing equilibrium as 'the reaction stopping'. Both reactions continue at equal rates — that is what dynamic means.
- Saying equilibrium means equal amounts of reactants and products. It means equal rates, not equal quantities.
- Explaining the Haber conditions only by yield. The chosen temperature is a compromise: a higher temperature lowers yield but raises rate.
This page maps the specification. The pages above teach it, and the Chemistry lessons hold the whole course — completely free.