Practical questions
You will complete eight required core practical activities if you are studying GCSE Chemistry, and 18 if you are studying GCSE Combined Science (five of these are in Chemistry).
You could be asked questions about the apparatus, methods, safety precautions, results, analysis and evaluation of these experiments.
There are three core practical activities in the Chemical changes section:
- investigate the change in pH when adding powdered calcium hydroxide or calcium oxide to a fixed volume of dilute hydrochloric acid
- investigate the preparation of pure, dry hydrated copper sulfate crystals, starting from copper oxide (including the use of a water bath)
- investigate the electrolysis of copper sulfate solution with inert electrodes and copper electrodes
Edexcel questions courtesy of Pearson Education Ltd.
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Dr Alex Lathbridge answers questions about practicals.
Sample question 1 – Foundation
Question
The fertiliser ammonium sulfate was made by reacting ammonia solution with dilute sulfuric acid. In the first step, 25 cm3 of dilute sulfuric acid was placed in a beaker.
Give the name of a piece of apparatus that could be used to measure out the 25 cm3 of dilute sulfuric acid.
[1 mark]
- Burette/pipette. [1]
Sample question 2 – Foundation
Question
Electrolysis is carried out on different solutions. Electricity is passed through each solution, as shown in the diagram.
State an improvement that can be made to the circuit to show that a current is flowing during the electrolysis.
[1 mark]
- Connect a lamp/ammeter in the circuit. [1]
Sample question 3 – Higher
Question
Lead sulfate is an insoluble salt. The method used to make the lead sulfate is:
- Pour 100 cm3 lead nitrate solution into a beaker.
- Add drops of sodium sulfate solution until a precipitate is seen.
- Allow the precipitate to settle to the bottom of the beaker.
- Pour off the liquid.
- Use a spatula to transfer the solid lead sulfate onto a filter paper.
Explain two ways of improving this experimental method to increase the amount and quality of lead sulfate obtained from the same volume of lead nitrate solution.
[3 marks]
Two improvements with their reason, eg two from:
- add excess sodium sulfate solution rather than a few drops [1] so more reaction occurs to form more lead sulfate [1]
- filter the reaction mixture rather than pour off the liquid [1] so none of the lead sulfate is lost on separation [1]
- wash the lead sulfate [1] so the impurities are removed [1]
- place the lead sulfate in an oven/warm place [1] so the lead sulfate is dry [1]
Sample question 4 – Higher
Question
Ammonium nitrate is produced from ammonia and nitric acid on a large scale in industry.
Ammonium nitrate can also be made in the laboratory by titrating ammonia solution with dilute nitric acid solution:
NH3(aq) + HNO3(aq) → NH4NO3(aq)
Ammonium nitrate crystals can then be obtained by heating to evaporate the water from the solution.
Give two reasons why this laboratory method is not suitable for use on a large scale in industry.
[2 marks]
- Volumes of solution are too large for titration method. [1]
- Large volumes of liquid need to be heated and then allowed to crystallise. [1]
