Chemistry study notes
Chemical Equilibria
Explain a changing equilibrium, calculate its composition and connect the Haber process to rate and yield.
A-Level 8873, revised syllabus (2026-2027)
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Learning outcomes
8. Chemical Equilibria (8873, 2026 revision; examinations 2026 and 2027). Use the outcome map to find the explanation for a particular syllabus requirement.
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8(a) Explain reversible reactions and dynamic equilibrium.
- Both directions occur; equal forward and reverse rates give constant concentrations in a closed system.
8(b) Apply Le Chatelier's Principle qualitatively.
- State the principle; deduce concentration, pressure and temperature responses from supplied information.
Predict the response to a disturbanceChoose a useful production rate and yield
8(c) Identify changes that affect the equilibrium constant.
- Concentration, pressure and catalysts do not change Kc at fixed temperature; temperature does.
Predict the response to a disturbanceKc describes an equilibrium ratioChoose a useful production rate and yield
8(d) Deduce concentration equilibrium expressions.
- Correct species, coefficient powers and concentration units.
8(e) Calculate concentration equilibrium constants.
- Use equilibrium data and stoichiometry where needed.
Kc describes an equilibrium ratioUse the equation to link all the changes
8(f) Calculate equilibrium quantities.
- Use supplied data; no solving of quadratic equations is required.
8(g) Explain the Haber process conditions.
- Industrial compromise: temperature, pressure, iron catalyst, separation and recycling.