4.3.3 Using Electrolysis to Extract Metals

• Metals can be extracted from molten compounds via what?

  Electrolysis.
• When is electrolysis used?

  When the metal is too reactive to be extracted by reduction with carbon or if the metal reacts with carbon.
• How big are the amounts of energy used in the extraction process?

  Large.
• Why is electrolysis not used to extract all metals?

  Electrolysis is expensive because it requires a large amount of electricity.
• When should a metal be extracted by carbon reduction?

  When the metal is less reactive than carbon.
• Which method of metal extraction would be used to extract iron?

  Reduction with carbon.

  
• Why is electrolysis used to extract aluminium from its ores?

  It is more reactive than carbon.
• What is the name of the substance that is mixed with aluminium oxide to lower its melting point?


  Cryolite.
• Why is cryolite used to lower the melting point of aluminium oxide?

  To lower costs.
• _Al2O3 ➔_Al +_O2

  2, 4, 3.
• In electrolysis, which electrode are the Al3+ ions attracted to?

  Cathode.
• During the electrolysis of molten aluminium oxide, are the O2- ions oxidised or reduced?

  Oxidised.
• How is aluminium manufactured?

  By the electrolysis of a molten mixture of aluminium oxide and cryolite using carbon as the anode.
• Why is a mixture used as the electrolyte in electrolysis?

  Contains free ions to conduct electricity.
• Why must the positive electrode be continually replaced?


  It is carbon therefore reacts regularly with oxygen to produce carbon dioxide.