Electrolysis of Aluminium Oxide

• What should you be able to describe by the end of the video on electrolysis?

  Why electrolysis is used to extract some metals
• What is the process used to extract aluminium from its compound?

  Electrolysis
• Why are metals more reactive than carbon extracted using electrolysis?

  Because they cannot be reduced by carbon
• What is the compound from which aluminium is extracted?

  Aluminium oxide
• Why is cryolite mixed with aluminium oxide during extraction?

  To lower the melting point and reduce energy costs
• What is the melting point of aluminium oxide?

  Approximately 2000° C
• What materials are the cathode and anode made of in the electrolysis setup?

  Graphite
• Why is graphite used for the electrodes in electrolysis?

  Because it is a good conductor of electricity and has a high melting point
• What happens to aluminium ions at the cathode during electrolysis?

  They gain three electrons to form aluminium atoms
• What type of reaction occurs at the cathode during the extraction of aluminium?

  A reduction reaction
• What is the half equation for the reaction at the cathode?

  $\text{Al}^{3+} +$$3e^- \rightarrow \text{Al}$
• What happens to oxide ions at the anode during electrolysis?

  They lose two electrons to form oxygen atoms
• What type of reaction occurs at the anode during the extraction of aluminium?

  An oxidation reaction
• What is the half equation for the reaction at the anode?

  $\text{O}^{2-} \rightarrow \text{O} +$$2e^-$
• What do the oxygen atoms formed at the anode do?

  They pair up to form oxygen molecules, O2
• Why must the anode be replaced regularly during electrolysis?

  Because it reacts with oxygen to form carbon dioxide
• What are the two reasons why producing metals by electrolysis is expensive?

  High energy required to melt compounds and to produce electric current
• What is the temperature of the electrodes during the electrolysis process?

  Around 900° C
• What are the steps involved in the extraction of aluminium by electrolysis?

  1. Aluminium oxide is mixed with cryolite to lower the melting point.
  2. An electric current is applied to the molten mixture.
  3. Aluminium ions move to the cathode and gain electrons to form aluminium.
  4. Oxide ions move to the anode and lose electrons to form oxygen.
  5. Oxygen atoms pair up to form O2 molecules.
  6. The anode must be replaced regularly due to reaction with oxygen.
• What are the key differences between reduction and oxidation reactions in the context of electrolysis?

  • Reduction: Gain of electrons (e.g., aluminium ions at the cathode)
  • Oxidation: Loss of electrons (e.g., oxide ions at the anode)