Solubility Rules (Edexcel IGCSE Chemistry)
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Spec point — know the general rules for predicting the solubility of ionic compounds in water: • common sodium, potassium and ammonium compounds are soluble • all nitrates are soluble • common chlorides are soluble, except those of silver and lead(II) • common sulfates are soluble, except for those of barium, calcium and lead(II) • common carbonates are insoluble, except for those of sodium, potassium and ammonium • common hydroxides are insoluble except for those of sodium, potassium and calcium (calcium hydroxide is slightly soluble).
Solubility rules
- Ionic compounds are generally soluble in water compared to covalent substances, but there are exceptions
- A knowledge of the solubility of ionic compounds helps us to determine the most appropriate method for the preparation of salts
- The solubility of common ionic compounds is shown below:
Solubility of the common salts
| Salts | Soluble | Insoluble |
|---|---|---|
| Sodium, potassium and ammonium | All | None |
| Nitrates | All | None |
| Chlorides | Most are soluble | Silver and lead(II) |
| Sulfates | Most are soluble | Barium, calcium and lead(II) |
| Carbonates | Carbonates of sodium, potassium and ammonium | Most are insoluble |
| Hydroxides | Hydroxides of sodium potassium and ammonium (calcium hydroxide is sparingly soluble) | Most are insoluble |
- Note that calcium hydroxide is slightly soluble in water
Exam Hint Calcium hydroxide solution is more commonly know as limewater and is used to test for carbon dioxide.
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