Electrolysis of Copper Sulfate (Oxford AQA IGCSE Chemistry)

Required Practical: Electrolysis of Copper Sulfate

Introduction

• To electrolyse copper(II) sulfate solution using inert(graphite) electrodes followed by the use of copper electrodes

Apparatus

• 250 cm³ beaker

• 2 graphite electrodes

• Beaker suitable for electrolysis

• 12 V DC. power supply  

• Leads and crocodile clips

• 400 cm³ copper(II) sulfate, about 0.5 mol dm^–3  

Diagram

Electrolysis of copper(II) sulfate using graphite electrodes

Method

Graphite electrodes

1. Pour copper(II) sulfate solution into a beaker

2. Place two graphite rods into the copper sulfate solution

3. Attach one electrode to the negative terminal of a DC supply, and the other electrode to the positive terminal

4. Completely fill two small test tubes with copper(II) sulfate solution and position a test tube over each electrode as shown in the diagram

5. Turn on the power supply and observe what happens at each electrode

6. Test any gas produced with a glowing splint and a burning splint

7. Record observations of what happens at each electrode, including the results of the gas tests

Practical tip

• The anode will always be the one where gas is produced, which means that you will see bubbles

Analysis of Results

Results table

Evaluation

• Copper metal is formed at the negative electrode and oxygen gas is formed at the positive electrode

Conclusion

• Copper ions are attracted to the negative electrode and are reduced (gain electrons)

  • Cu²⁺ (aq) + 2e^– → Cu (s)

• At the positive electrode, oxygen gas is formed.

  • The equation for this reaction is:

    • 2OH^– (aq) →  O₂ (g) + 2H⁺ (aq) + 4e^–