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Chemical Changes

Electrolysis of copper sulfate solution

  • 2 things to know
  • Paper 3

Overview

How the anode loses mass and the cathode gains it when copper sulfate solution is electrolysed with copper electrodes, why the blue colour stays, and purifying copper with an impure anode, a pure cathode and copper sulfate electrolyte.

What you need to know

Answer each one before you reveal it.

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Key term

Describe what happens at each electrode when copper is purified by electrolysis of copper sulfate solution with copper electrodes.

Key term

Describe what happens to the mass of the anode when copper sulfate solution is electrolysed using copper electrodes.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Describe what happens to the mass of the anode when copper sulfate solution is electrolysed using copper electrodes.

    Model answer

    The anode loses mass as copper from it goes into the solution.

  2. 2

    Describe what happens to the cathode when copper sulfate solution is electrolysed using copper electrodes.

    Model answer

    It gains mass as a fresh layer of copper builds up on it.

  3. 3

    Explain why the blue colour of the solution does not fade when copper sulfate solution is electrolysed with copper electrodes.

    Model answer

    Copper ions enter the solution from the anode as fast as they are removed at the cathode.

  4. 4

    State which electrode is made of impure copper when copper is purified by electrolysis.

    Model answer

    The anode is made of the impure copper.

  5. 5

    State what the cathode is made from when copper is purified by electrolysis.

    Model answer

    The cathode is a thin sheet of pure copper.

  6. 6

    Explain what happens to the impurities in the copper during electrolytic purification.

    Model answer

    The impurities do not go into solution and collect as a sludge beneath the anode.

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