Preparing Insoluble Salts (Cambridge O Level Chemistry)
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Preparing Insoluble Salts
- Insoluble salts can be prepared using a precipitation reaction
- The solid salt obtained is the precipitate, thus in order to successfully use this method the solid salt being formed must be insoluble in water, and the reactants must be soluble
Using two soluble reactants
Diagram showing the filtration of the mixture to remove the precipitate
Method:
- Dissolve soluble salts in water and mix together using a stirring rod in a beaker
- Filter to remove precipitate from mixture
- Wash filtrate with distilled water to remove traces of other solutions
- Leave in an oven to dry
Example: Preparation of pure, dry lead(II) sulfate crystals using a precipitation reaction
Soluble Salt 1 = lead(II) nitrate
Soluble Salt 2 = potassium sulfate
Method:
- Dissolve lead(II) nitrate and potassium sulfate in water and mix together using a stirring rod in a beaker
- Filter to remove precipitate from mixture
- Wash precipitate with distilled water to remove traces of potassium nitrate solution
- Leave in an oven to dry
Equation of reaction:
lead(II) nitrate + potassium sulfate → lead(II) sulfate + potassium nitrate
Pb(NO3)2 (aq) + K2SO4 (aq) → PbSO4 (s) + 2KNO3 (aq)
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