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Solubility rules for ionic compounds

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A few simple rules tell you whether a salt dissolves in water. You need them to plan how to make salts.

The rules

Using the rules

If two solutions are mixed and an insoluble combination of ions is possible, a precipitate forms.
Example: silver nitrate solution + sodium chloride solution gives a white precipitate of silver chloride.

Tips for remembering

Start with the 'always soluble' groups: sodium, potassium, ammonium and nitrates.
Then learn the exceptions for chlorides (silver, lead) and sulfates (barium, calcium, lead).
Worked example

Barium chloride solution is mixed with sodium sulfate solution. Will a precipitate form?

  1. Possible new pairs: barium sulfate and sodium chloride.
  2. Barium sulfate is an insoluble sulfate.
  3. Sodium chloride is soluble.

Answer: Yes, a white precipitate of barium sulfate.

Key idea

Sodium, potassium and ammonium compounds and all nitrates are soluble. Chlorides are soluble except silver and lead(II). Sulfates are soluble except barium, calcium and lead(II). Carbonates and hydroxides are insoluble except sodium, potassium and ammonium (carbonates) or sodium, potassium and calcium (hydroxides).

The interactive lesson includes the diagrams for this topic.

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