AQA GCSE Chemistry

Revision Notes

4.3.5 Required Practical: Electrolysis of Aqueous Solutions

Required Practical 3: Electrolysis of Aqueous Solutions

Objective:
To investigate what happens when aqueous solutions are electrolysed using inert electrodes

Hypothesis:
A metal will be produced at the negative electrode because metal ions are positive

Materials:

  • Test tubes
  • Electrolyte solutions
  • 100 cm3 beaker
  • Stand and clamp
  • Two carbon rod electrodes
  • Two crocodile / 4 mm plug leads
  • Low voltage power supply
  • Blue litmus paper

Electrolysis - Apparatus Inverted Test Tubes, IGCSE & GCSE Chemistry revision notes

Diagram showing the electrolysis of aqueous solutions

Practical Tip:
Make sure the test tubes do not cover the electrodes completely and fall to the bottom of the cell or the conductivity will fall considerably and the rate of electrolysis will be very slow

Method:

  1. Set up the apparatus as shown in the diagram
  2. Add the aqueous solution to the beaker
  3. Add two graphite rods as the electrodes and connect this to a power pack or battery
  4. Turn on the power pack or battery and allow electrolysis to take place
  5. Record the results in a suitable table (see below) and repeat for another solution, checking the electrodes in between runs to see if any metal has been deposited
  6. The following aqueous solutions are suitable for this investigation: copper chloride, copper sulfate, sodium chloride, sodium bromide, sodium nitrate
  7. The gases produced can be collected in the test tubes to be tested later

Results: Record your results in a suitable table:

Electrolysis of Aqueous Solutions Table

Investigating Electrolysis of Aqueous Solutions Table, downloadable IGCSE & GCSE Chemistry revision notes

Evaluation:
The gases and corresponding tests are:

  • Hydrogen – lighted splint goes out with a squeaky pop
  • Oxygen – a glowing splint relights
  • Chlorine – damp blue litmus paper turns red and is then bleached white

Conclusion:
Describe how the results obtained compare with the expected results based on the hypothesis

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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