Required Practical: Separating Mixtures
Chemistry: AQA GCSE Higher, topic 4.3.5
Required Practical - Separating Mixtures
The aim of this practical is to produce a pure, dry sample of a soluble salt from an insoluble oxide or carbonate.
Preparation
- Use a Bunsen burner to gently warm the acid.
- Add the insoluble solid (with stirring) until the reaction no longer happens.
Filtration
- Filter the solution to remove the excess insoluble solid.
- This will leave a solution of the salt dissolved in water.
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Crystallisation
- Heat the solution in an evaporating basin above a beaker of water.
- The 'water bath' ensures gentle heating.
- Let the solution cool and allow more water to evaporate.
- As water evaporates, the solution will become more concentrated and the salt will begin to crystallise.
Test yourself on Required Practical: Separating Mixtures
Why can filtration not be used to separate a dissolved salt from water?
Why does the dissolved salt begin to crystallise as the solution cools and water evaporates?
Why is an insoluble oxide or carbonate reacted with the acid, rather than a soluble substance?
Why must the reaction mixture be filtered before the crystallisation stage can begin?
Why is the insoluble solid added to the acid until no more of it reacts, rather than adding one fixed amount?