GCSE Combined Science (AQA)

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Electrolysis of Solutions

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Chemical changes Electrolysis

Electrolysis of Solutions

9:59 Electrolysis of Ionic Compounds and Aluminium Extraction
Spec 4.4.3.4
Previous H+ Concentration and pH Next Communities & Ecosystems
  • Water molecules can break down into hydrogen ions (H+) and hydroxide ions (OH-).
  • Electrolysis involves separating positive and negative ions in a compound to convert them into atoms or molecules.
  • In electrolysis, two conducting electrodes are submerged in an ionic solution or molten compound to create a circuit.
  • The positive anode loses electrons, while the negative cathode gains electrons.
  • During electrolysis, H+ ions travel to the negative cathode, and OH- ions travel to the positive anode due to opposite charges attracting.
  • All ions, including hydrogen and hydroxide ions, must be considered in the electrolysis of an aqueous solution like sodium chloride.
  • At the cathode, either hydrogen ions or metal ions can be discharged depending on their reactivity.
  • The reactivity series helps determine which ions are discharged; metals more reactive than hydrogen will not be discharged.
  • Sodium is more reactive than hydrogen, so hydrogen ions are discharged at the cathode, forming H2 gas.
  • Copper is less reactive than hydrogen, so copper ions are discharged at the cathode, forming copper metal.
  • At the anode, if halide ions are present, they are discharged, producing halogen gas.
  • If no halide ions are present, hydroxide ions are discharged, producing oxygen gas.
  • In the electrolysis of copper sulfate solution, copper metal forms at the cathode, and oxygen forms at the anode.

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