Topic 4 - Extracting Metals and Equilibria

• Series of reactivity:

  POtassium > Sodium > Calcuim > Magnesium > Aluminium > Carbon > Zinc > Iron > Hydrogen > Copper > Silver > GOld
• For higher reactivity: easier to form cation and less resistant to oxidation

  For lower reactivity: fo not eaily form cation and more resistant to oxidation
• Potasium, Sodium and Calcium:

  • vigorous reaction with water - forms metal hydroxide and hydrogen
  • Explosive with dilute acid - form salt and hydrogen
• Magnesium and Aluminium:

  • reacts with steam but not water - forms metal oxide and hydrogen
  • vigorous reaction with dilute acid - form salt and hydrogen
• Zinc and Iron:

  • reacts with steam but not water - forms metal oxide and hydrogen
  • with dilute acid, some bubbling form salt and hydrogen
• Copper, Silver and Gold:

  • no reaction at all
• Displacement reaction: when a more reactive element takes the place of a less reactive metal in a compund
• Redox reaction: Where one substance in a reaction is reduced and another is oxidised.
• Oxidation = gain of oxygen or loss of electron

  Reduction = gain of electron or loss of oxygen
• Most metals are extracted from ores taken from the earths crust
• Electrolysis: used for metals more reactive than carbon

  They are expensive and require a lot of energy
• Reduction using carbon: can only be used to extract metal less reactive than carbon

  HEating the ores with carbons reduce it, oxygen is removed
• Silver and Gold are foud as uncombined element
• Biological method of extraction:

  Photoextraction:

  1. soil contain metal compunds
  2. metals build up in leaves
  3. harvasted plant are burned, ashes countain metal compund

  Bacterial (Bioleaching)

  1. low grade ore is put with bacteria
  2. bacteria get energy from bond between atom in the ore, seperating out the metal in process
• Biological method compare to the traditional method (electrolysis and displacement reaction) :

  • can be used to extract metals from low - grade ore or from waste
  • doesn't produce CO2
  • it is slow
• Extraction by electrolysis:

  • cathode with aluminium ore and anode
  • anode attract oxygen and oxygen gas is formed
  • molten aluminium if formed
  • the solution is made with cryolite to lower the melting point of alumiium to make the energy reqired for electrolysis lesser
• Issues with extracting metals:

  • metals are non-renewable resources, they will eventually run out
  • mining metal damage the environment
  • fossil fuel needs burning to provide a lot of energy for extraction, causing pollution
• Benefit of recycling metal:

  • reduce the amount of waste send t landfill
  • reduce the need for mining, preserve the finite amount of metal
  • uses less energy than mining and extracting raw material
  • produce less CO2 = greenhouse gas = global warming
• LIfe cycle assessment: An assessment of the environmental impact of a product over each stage of life
• LCA:

  • Raw material:

  -metals need mining and extraction from ores

  -raw material often come from crude oil (non-renewable)

  • manufacturing

  -use a lot of energy and cause pollution

  -waste roduct need recycling or deposed of

  • using the product

  -could damage the environment by relasing toxic fumes or greenhouse gas

  • Product disposal

  -dispose on landfill can take up space
• Why electrolysis are use to extract from it's ore:

  • aluminium is very reactive
  • needs a lot of energy
• How is copper extracted from copper oxide?

  • mix copper with carbon
  • heat it strongley until no further change