Separating Metals from Metal Oxides

• Most metals aren't found in the earth as pure lumps. Instead, you have to extract them from a compound meaning more work is required
• Metals often have to be separated from their oxides
• Lots of common metals, like iron and aluminium, react with oxygen to form oxides. This process is an example of oxidation. These oxides are often the ores that the metals need to be extracted from
• A reaction that separates a metal from its oxide is called a reduction reaction
• An ore is a type of rock that contains metal compounds
• Formation of metal ore:

  • Oxidation = gain of oxygen
  • E.g. magnesium is oxidised to make magnesium oxide = 2Mg + O2 -> 2MgO
• Extraction of metal:

  • Reduction = loss of oxygen
  • E.g. copper oxide is reduced to copper = 2CuO + C -> 2Cu + CO2
• Some metals can be extracted by reduction with carbon
• Some metals can be extracted from their ores chemically by reduction using carbon
• In this reaction, the ore is reduced as oxygen is removed from it, and carbon gains oxygen so is oxidised:

  Iron (III) oxide + carbon -> iron + carbon dioxide

  2Fe2O3 + 3C -> 4Fe + 3CO2
• The position of the metal in the reactivity series determines whether it can be extracted by reduction with carbon
• Metals higher than carbon in the reactivity sseries have to be extracted using electrolysis, which is expensive

  
• Metals below carbon in the reactivity series can be extracted by reduction using carbon. E.g. iron oxide is reduced in a blast furnace to make iron. This is because carbon can only take the oxygen away from metals which are less reactive than carbon itself is

  
• Some metals are so unreactive they are in the earth as the metal itself. E.g. gold is mined as its elemental form