electrolysis of aluminium oxide

• What is the purpose of electrolysis in metal extraction?

  To extract some metals from compounds
• Why is aluminium extracted using electrolysis?

  Because it is more reactive than carbon
• What is the compound used to extract aluminium?

  Aluminium oxide
• What is the melting point of aluminium oxide?

  Approximately 2000° C
• What compound is mixed with aluminium oxide to lower its melting point?

  Cryolite
• Why is cryolite added to aluminium oxide?

  To reduce energy needed for melting
• What materials are the electrodes made of in the electrolysis setup?

  Graphite
• Why is graphite used for electrodes in electrolysis?

  It conducts electricity and has a high melting point
• What ions are present in molten aluminium oxide?

  Aluminium ions $Al^{3+}$ and oxide ions $O^{2-}$
• What happens to aluminium ions at the cathode?

  They gain electrons to form aluminium atoms
• What is the half equation for the reaction at the cathode?

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

  They lose electrons to form oxygen atoms
• What is the half equation for the reaction at the anode?

  $O^{2-} \rightarrow \frac{1}{2}O_{2} +$$2e^{-}$
• What do the oxygen atoms formed at the anode do?

  They pair up to form oxygen molecules $O_{2}$
• Why must the anode be replaced regularly?

  It reacts with oxygen to form carbon dioxide
• What gas is produced when oxygen reacts with graphite at the anode?

  Carbon dioxide
• Why is electrolysis expensive for metal production?

  It requires a lot of energy for melting and electricity
• What are the two main energy costs in electrolysis?

  Melting the compound and producing electric current
• What are the steps involved in the electrolysis of aluminium oxide?

  1. Aluminium oxide is mixed with cryolite.
  2. Electric current is applied to molten aluminium oxide.
  3. Aluminium ions $Al^{3+}$ move to the cathode and gain electrons.
  4. Oxide ions $O^{2-}$ move to the anode and lose electrons.
  5. Oxygen atoms pair to form $O_{2}$ molecules.
  6. Anode must be replaced due to reaction with oxygen.
• What are the differences between reduction and oxidation in electrolysis?

  • Reduction: Gain of electrons (at cathode)
  • Oxidation: Loss of electrons (at anode)
• What are the properties of graphite that make it suitable for electrodes in electrolysis?

  • Good conductor of electricity
  • High melting point
  • Stable at high temperatures
• What are the implications of using electrolysis for metal extraction?

  • High energy costs
  • Requires careful management of resources
  • Environmental considerations due to gas emissions