Topic 3 - Archived

• All metals are found in the Earth's crust
• Some unreactive metals are found by themselves as pure metals ("native"), such as gold and silver. Other metals are found as ores (in rocks) chemically combined with another element, which is usually oxygen. For example, iron ore is iron oxide. Once the oxygen has been removed the metals has been extracted and can be used.
• Different metals have different reactivities (they react at different speeds). The reactivity of a metal controls the way it is removed from its ore (rock).
• A more reactive metal can displace a less reactive metal from its compound. The reaction is called a displacement reaction.
• Iron is removed from the ore (mostly iron oxide) using a blast furnace
• Extraction of Iron - Blast furnace:

  • Raw materials: coke, limestone, iron ore and hot air
  • Products: slag and molten iron
• In the extraction of iron in a blast furnace:

  • Iron ore is used as it is the source of the iron. It is added through the top of the furnace.
  • Coke (pure carbon) is the fuel and produces carbon monoxide. It is added through the top of the furnace.
  • Limestone (calcium carbonate) removes impurities. It is added through the top of the furnace.
  • Hot air is needed for the coke to burn (the source of the oxygen). It is added near the bottom of the furnace.
• Blast furnace reactions (1/3)

  Oxygen in the blasts of hot air reacts with coke (carbon) to form carbon dioxide. This is an example of a combustion reaction.

  Carbon + Oxygen -> Carbon Dioxide

  C + O₂ -> CO₂
• Blast furnace reactions (2/3)

  The carbon dioxide then reacts with coke (carbon) to produce carbon monoxide.

  Carbon + Carbon Dioxide -> Carbon Monoxide

  C + CO₂ -> 2CO
• Blast furnace reactions (3/3)

  The carbon monoxide then reacts with the iron ore (iron(III) oxide) to produce molten iron, which collects at the base of the furnace. The waste gases leave at the top of the furnace.

  Iron(III) Oxide + Carbon Monoxide -> Iron + Carbon Dioxide

  Fe₂O₃ + 3 CO -> 2 Fe + 3 CO₂

  The iron (III) oxide is reduced. The carbon monoxide is oxidised.
• Limestone reactions:

  The iron ore contains sand. This would make the iron weak so it must be removed. This happens in two steps.

  1. Firstly, the limestone (calcium carbonate) breaks down when healed to produce calcium oxide (and carbon dioxide). This is an example of a thermal decomposition reaction.
  2. The calcium oxide then reacts with the sand (silicon dioxide) to produce slag (calcium silicate). The molten slag floats on top of the molten iron and can be removed.