Using electrolysis to extract metals

• Higher placed metals (above carbon) have to be extracted using electrolysis as they are too reactive and cannot be reduced by carbon
• • Lower placed metals can be extracted by heating with carbon which reduces
• • Electrolysis is very expensive as large amounts of energy are required to melt the ores and produce the electrical current
• • Aluminium oxide has a very high melting point so it is first dissolved in molten cryolite producing an electrolyte with a lower melting point, as well as a better conductor of electricity than molten aluminium oxide
• Aluminium forms at the negative cathode

  Oxygen forms at the positive anode.
• The positive electrode is made from graphite (carbon) which reacts with the oxygen to produce carbon dioxide

  For this reason the anode must be continually replaced as it loses its mass