AQA GCSE Chemistry

Revision Notes

4.2.5 Required Practical: Preparation of a Soluble Salt

Required Practical 1: Preparation of a Soluble Salt

Objective:
To prepare a pure, dry sample of a soluble salt from an insoluble oxide or carbonate using a Bunsen burner and dilute acid

Hypothesis:
A salt can be prepared and separated by an acid-base neutralisation reaction

Materials:

  • 1.0 mol/dm3 dilute sulfuric acid
  • Copper (II) oxide
  • Spatula & glass rod
  • Measuring cylinder & 100cm3 beaker
  • Bunsen burner
  • Tripod, gauze & heatproof mat
  • Filter funnel & paper, conical flask
  • Evaporating basin and dish.

IGCSE & GCSE Chemistry revision notes

The steps in the preparation of a soluble salt

Practical Tip:
The base is added in excess to use up all of the acid, which would become dangerously concentrated during the evaporation and crystallisation stages

Method:

  1. Add 50cm3 dilute acid into a beaker and warm gently using a Bunsen burner
  2. Add the insoluble oxide slowly to the hot dilute acid and stir until the base is in excess (i.e. until the base stops dissolving and a suspension of the base forms in the acid)
  3. Filter the mixture into an evaporating basin to remove the excess base
  4. Gently heat the solution in a water bath or with an electric heater to evaporate the water and to make the solution saturated
  5. Check the solution is saturated by dipping a cold glass rod into the solution and seeing if crystals form on the end
  6. Leave the filtrate in a warm place to dry and crystallise
  7. Decant excess solution and allow the crystals to dry

Results:
Hydrated copper(II) sulfate crystals should be bright blue and regularly shaped

Evaluation:
Describe how your crystals compare to the description in the results section. If different suggest an explanation

Conclusion:
Acid-base reactions produce salt and water with the regular shape of the salt reflecting the ionic lattice structure in its bonding

Exam Tip

Make sure you learn the names of all the laboratory apparatus used in the preparation of salts.

Author: Francesca

Fran has taught A level Chemistry in the UK for over 10 years. As head of science, she used her passion for education to drive improvement for staff and students, supporting them to achieve their full potential. Fran has also co-written science textbooks and worked as an examiner for UK exam boards.
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