GCSE Chemistry (AQA)

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Electrolysis of Molten Ionic Compounds

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Chemical changes Electrolysis

Electrolysis of Molten Ionic Compounds

5:31 Electrolysis of Ionic Compounds and Aluminium Extraction
Spec 4.4.3.2
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  • Simple ionic compounds can be separated into ions using electrolysis when in a molten state.
  • Each molecule in a simple ionic compound consists of two ions, one positive and one negative, held together by opposite charges.
  • Example: Electrolysis setup to separate lead and bromine from lead bromide.
  • Molten lead bromide allows charged ions to move freely, making it an electrolyte that can carry an electric current.
  • Graphite electrodes are used as they are good conductors and do not react with lead bromide.
  • Electrodes are connected to a power supply to create a complete circuit.
  • Metal is produced at the cathode, which gains a negative charge from the power supply.
  • Lead ions (Pb2+) are attracted to the negatively charged cathode, gain electrons, and form neutral lead atoms.
  • Liquid lead metal collects at the bottom.
  • Non-metal is produced at the anode, which is positively charged.
  • Bromide ions (Br-) are attracted to the positively charged anode, lose electrons, and form bromine gas (Br2).
  • Bubbles of bromine gas form at the anode.
  • Predicting products of electrolysis involves identifying ions present and their charges.
  • Example: Electrolysis of molten potassium chloride.
  • Potassium chloride consists of potassium ions (K+) and chloride ions (Cl-).
  • Potassium ions are attracted to the cathode, forming potassium metal.
  • Chloride ions are attracted to the anode, forming chlorine gas (Cl2).

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