‹ Chemistry simulationsChemistry · AS Level 9701 · 7 EquilibriaSix simulations covering Topic 7: dynamic equilibrium particle by particle, Le Chatelier and the Haber process with yields from the real equilibrium constant, Kc from an ICE table, Kp and the dissociation of dinitrogen tetroxide, strong and weak acids with the pH scale, and pH titration curves with indicator ranges.
In a closed system a reversible reaction reaches a point where the forward and backward reactions run at the same rate. Nothing stops: the concentrations stay constant only because every conversion one way is matched by one the other way. Watch the particles switch and the graph level off.
N₂ + 3H₂ ⇌ 2NH₃, ΔH = −92 kJ mol⁻¹. Change the pressure or the temperature and the position of equilibrium moves to oppose the change. The yield shown is calculated from the real equilibrium constant, so you can see why industry compromises at about 450 °C and 200 atm with an iron catalyst.
Kc is the ratio of product to reactant concentrations at equilibrium, each raised to its coefficient. It depends only on temperature. Fill in what was there at the start and how much of one species is left at equilibrium, and the ICE table does the rest.
For gases the equilibrium constant is written with partial pressures. N₂O₄ ⇌ 2NO₂ has Kp = 0.15 atm at 25 °C. Squeeze the mixture and it turns paler as the equilibrium shifts to the side with fewer molecules, yet Kp stays the same. Check the numbers.
A Brønsted-Lowry acid donates a proton; a base accepts one. A strong acid is fully ionised in water; a weak acid sets up an equilibrium with only a small fraction ionised. Compare the beakers and the pH.
As base is added to an acid the pH climbs slowly, jumps steeply near the equivalence point, then levels off. The shape depends on whether the acid and base are strong or weak, and an indicator only works if its colour change falls inside the steep part.
Dynamic equilibrium particle by particle with a rate graph, Le Chatelier and the Haber process with yields from the real equilibrium constant, Kc from an ICE table, Kp and the dissociation of dinitrogen tetroxide in 3D, strong against weak acids with the pH scale, and pH titration curves with indicator ranges.
Six simulations covering Topic 7: dynamic equilibrium particle by particle, Le Chatelier and the Haber process with yields from the real equilibrium constant, Kc from an ICE table, Kp and the dissociation of dinitrogen tetroxide, strong and weak acids with the pH scale, and pH titration curves with indicator ranges.
Equilibria is a free, browser-based simulation for Cambridge International AS & A Level Chemistry 9701 (topic 7 Equilibria). The same ideas are examined in Cambridge IGCSE Chemistry 0620 (topic 7 Acids, bases and salts, topic 6 Chemical reactions). The course is assessed in Paper 1 (Multiple Choice (AS)), Paper 2 (AS Structured), Paper 3 (Advanced Practical), Paper 4 (A Level Structured), Paper 5 (Planning, Analysis, Evaluation). Syllabus for examination in 2025-2027. There are 6 tabs, each a self-contained experiment with its own controls and live readings, and nothing to install: it runs on a laptop, tablet or classroom projector.
Full syllabus map: AS Level Chemistry 9701 topic 7.
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