Electrolysis of Copper Sulphate

A series of free IGCSE Chemistry Activities and Experiments (Cambridge IGCSE Chemistry).

Electrolysis of Copper(II) Sulphate Solution
This experiment is designed to demonstrate the different products obtained when the electrolysis of copper(II) sulfate solution is carried out first with inert graphite electrodes and then with copper electrodes. The use of copper electrodes illustrates how copper is refined industrially.

Using Graphite Rods

1. Set up an electrolysis cell using graphite rods as electrodes and copper(II) sulphate solution as electrolyte.
2. At the anode: Bubbles of gas (oxygen) are formed at the anode.
   Anode reaction: 4OH^-(aq) → O₂(g) + 2H₂O(l) + 4e^-
3. At the cathode: A deposit of copper forms on the cathode; this will often be powdery and uneven.
   Cathode reaction: Cu²⁺(aq) + 2e^- → Cu(s)

Using Copper Plates (Refining Copper)

1. Replacing the graphite rods with clean copper plates produces a different anode reaction.
2. At the anode: No oxygen is produced, rather the copper anode dissolves.
   Anode reaction: Cu(s) → Cu²⁺(aq) + 2e^-
3. At the cathode: A deposit of copper forms on the cathode.
   Cathode reaction: Cu²⁺(aq) + 2e^- → Cu(s)
   During this electrolysis, the mass gained of copper at the cathode is equal to the mass lost at the anode.
   

Electrolysis in the Lab

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Question:

1. Using a table, highlight the similarities and differences between using graphite electrodes and copper electrode for the electrolysis of copper sulphate.

Check out the following link to find out how electrolysis can be used for electroplating. Electroplating

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