‹ Chemistry simulationsChemistry · A Level 9701 · 27 Group 2 (A Level)Four simulations covering Topic 27: a carbonate ion in 3D with each Group 2 cation beside it, showing how a small, highly charged cation drags the electron cloud out of the anion; heating Group 2 carbonates and nitrates with a temperature slider to find when each one finally decomposes; lattice enthalpy set against hydration enthalpy as you move down the group for sulfates and hydroxides; and a solubility bench where sulfuric acid and sodium hydroxide are added to Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺ solutions.
A positive ion attracts the electron cloud of a neighbouring anion and pulls it out of shape. A small cation with a 2+ charge has a high charge density and distorts the carbonate ion strongly; a large cation spreads the same charge over more volume and distorts it less. The cation is held at the same distance each time so you can compare the stretch directly.
Heat a sample of each salt in a test tube and pass any gas given off through limewater. Raise the flame temperature and wait for the sample to catch up: the salt does nothing until it passes its own decomposition temperature, and that temperature climbs as you go down the group.
To dissolve a solid you pay the lattice enthalpy to pull the ions apart and get back the hydration enthalpies as water surrounds them. The bar above the line is the energy you pay, the bar below is the energy you get back. Whichever falls faster as the cations get bigger decides whether the salt gets more or less soluble.
Four test tubes hold solutions of magnesium, calcium, strontium and barium ions. Add dilute sulfuric acid and the heavier the metal the more precipitate you get; add sodium hydroxide and it runs the other way. Each white sphere is a cluster of precipitate settling to the bottom.
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Four interactive simulations for Cambridge A Level Chemistry 9701 topic 27 Group 2: the polarisation of a carbonate ion by Mg2+, Ca2+, Sr2+ and Ba2+ drawn in 3D with charge density worked out for each cation, a heating test for Group 2 carbonates and nitrates with a temperature slider, limewater and the decomposition equations, an energy-bar comparison of lattice enthalpy and hydration enthalpy that explains why sulfates become less soluble and hydroxides more soluble down the group, and a test-tube bench showing the precipitates formed with dilute sulfuric acid and sodium hydroxide.
Four simulations covering Topic 27: a carbonate ion in 3D with each Group 2 cation beside it, showing how a small, highly charged cation drags the electron cloud out of the anion; heating Group 2 carbonates and nitrates with a temperature slider to find when each one finally decomposes; lattice enthalpy set against hydration enthalpy as you move down the group for sulfates and hydroxides; and a solubility bench where sulfuric acid and sodium hydroxide are added to Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺ solutions.
Group 2 trends is a free, browser-based simulation for Cambridge International AS & A Level Chemistry 9701 (topic 27 Group 2). 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 4 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: A Level Chemistry 9701 topic 27.
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