Extraction by Electrolysis (SQA National 5 Chemistry): Revision Note

Electrolysis of ionic compounds

• Electrolysis is the process of breaking down (decomposing) an ionic compound into its elements using electricity

• For electrolysis to work, the ionic compound must be in a state where its ions are free to move

  • This means it must be either molten (melted into a liquid) or dissolved in water (in an aqueous solution)

• This conductive liquid or solution is called the electrolyte

Basic electrolysis set up

• The setup requires:

  • An electrolyte (the molten or dissolved ionic compound)

  • Two conductive rods called electrodes, which are placed into the electrolyte

  • A direct current (DC) power supply to connect the electrodes

Ion movement

• When the power is switched on, the charged ions in the electrolyte start to move

  • Positive ions are attracted to the negative electrode

  • Negative ions are attracted to the positive electrode

Redox at the electrodes

• When the ions reach the electrodes, redox reactions occur

• At the negative electrode, positive ions gain electrons

  • This is reduction

• At the positive electrode, negative ions lose electrons

  • This is oxidation