A substance's solubility is a measure of the maximum mass that will dissolve in a given volume of solvent, at a particular temperature. Substances that are very soluble have high solubilities. Substances that are insoluble or sparingly soluble (almost none dissolves) have low solubilities.
The table summarises whether common ionic compounds are soluble or insoluble in water.
|All common sodium, potassium and ammonium salts|
|Most common chlorides||Silver chloride, lead chloride|
|Most common sulfates||Lead sulfate, barium sulfate, calcium sulfate|
|Sodium carbonate, potassium carbonate, ammonium carbonate||Most common carbonates|
|Sodium hydroxide, potassium hydroxide, ammonium hydroxide||Most common hydroxides|
For example, a precipitate of lead iodide forms when potassium iodide solution and lead nitrate solution are mixed:
potassium iodide + lead nitrate → potassium nitrate + lead iodide
2KI(aq) + Pb(NO3)2(aq) → 2KNO3(aq) + PbI2(s)
The formation of a precipitate, when two solutions are mixed, can be predicted using the solubility rules in the table:
Silver nitrate solution is mixed with sodium chloride solution. Predict whether a precipitate forms, and name any precipitate.
A precipitate of silver chloride will form.
Potassium sulfate solution is mixed with barium chloride solution. Predict whether a precipitate forms, and name any precipitate.
A precipitate of barium sulfate will form.