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Displacement Reactions and the Reactivity Series
Look at the reaction below:
Here, we witness iron and copper competing to be compounds in solution. Iron wins as it displaces copper from copper sulphate solution. Green iron II sulphate is formed.
Other metals displace less reactive metals in a similar manner.
A compound will always displace a less reactive metal from solutions of its compounds.
Another example of 'competition' between metals to form compounds is observed in the reaction between metals and metal oxides.
Observe the reaction between iron and copper oxide, mixed and heated strongly.
Iron displaces the copper from the oxide - in fact iron is behaving as a reducing agent, since it is removing oxygen from the other metal.
Other metals compete in a similar way. The general rule is:
|When a metal is heated with the oxide of a less reactive metal, it will displace the metal from it.|
By comparing the reactions of metals in oxygen, water and acid, metal oxides and solutions of metal salts, we can arrange metals into a list of reactivity called the Reactivity Series.
The more reactive a metal is the more likely it is to form a compound.
The more reactive a metal, the more stable its compound.
The more reactive a metal the more difficult it is to extract from its compounds.
Copper, silver and gold appear as elements in the earth due to their unreactivity with their environment. They are easy to extract.
Reactive metals are more difficult to extract. They are often found as compounds or ores.
A method of extraction known as Electrolysis is used to remove the element from the remaining compound.