Required practical: Electrolysis of solutions (e.g. copper sulfate) with inert electrodes

Aim

To observe electrolysis of an aqueous ionic compound, identify products at each electrode, and link to ion discharge rules.

Method (step-by-step)

1. Set up d.c. supply with inert electrodes (graphite) in electrolyte.
2. Note observations at anode and cathode (gas, colour changes, mass change if copper plating).
3. Keep current roughly stable if comparing time; rinse and dry electrodes before massing.
4. Write half-equations where required (O₂ at anode from OH⁻ in sulfate solution, etc., depending on setup).

Equipment

• Power pack
• graphite rods
• beaker
• wires
• electrolyte

Variables

• Independent: Electrolyte or electrode material (if comparing).
• Dependent: Mass change / volume of gas / observation.
• Control: Current; time; volume of solution

Results & analysis

Relate products to reactivity series vs H⁺ in aqueous solution; explain preferential discharge.

Graphs & interpretation

Usually qualitative / mass gain table rather than a plotted graph at GCSE.

Exam-style question prompts

• Explain what happens at the cathode in CuSO₄ solution with graphite electrodes.

Exam tips

• OIL RIG for electron direction
• Link to ionic equations

Related topic revision

• Electrolysis
• Electrolysis of aqueous solutions