Precipitation and ionic equations sim
Mix drops of thirteen solutions on a spotting tile, see which pairs make a precipitate and why the spectator ions drop out, build the ionic equation, and graph how much solid forms.
Equations: precipitation, solubility rules and ionic equations · covers the O-Level, IGCSE, GCSE topic
What the sim shows
When two solutions of ionic compounds are mixed, four kinds of ion meet. Each solution's own pair was already dissolved, so only the two new pairs can form a solid: the cation of one solution with the anion of the other. If a new pair is insoluble, it comes out of solution as a precipitate; the other ions stay dissolved, unchanged, and are called spectator ions. The ionic equation leaves the spectators out and shows only the ions that form the solid, with state symbols: for example Pb²⁺(aq) + 2I⁻(aq) → PbI₂(s). It must balance in atoms and in charge. The solubility rules: all sodium, potassium and ammonium salts and all nitrates are soluble; chlorides (and iodides) are soluble except silver and lead(II); sulfates are soluble except barium, lead(II) and calcium (slightly); carbonates and hydroxides are insoluble except sodium, potassium and ammonium (calcium hydroxide is slightly soluble). Every bottle is 0.1 mol/dm³. In the graph, 10.0 cm³ of one solution is in the boiling tube and the other is added 1.0 cm³ at a time; the mass is what the precipitate would weigh after filtering, washing and drying. It rises until the ion in the tube is used up, then levels off. Model limits: every precipitate forms at once and completely; the dried mass is worked out from the moles, not weighed; real cases that break the simple rules are shown and explained (silver oxide, silver sulfate, barium hydroxide, iron(III) with carbonate, copper(II) and iron(III) with iodide).
- Spotting tile: one drop of each solution in a well
- Dropper bottles 1–13: all 0.1 mol/dm³
- Boiling tube: 10.0 cm³, then 1.0 cm³ portions for the graph
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