Higher and foundation tier
Displacement reactions are a clear way to demonstrate the order of reactivity of metals. In a displacement reaction a more
reactive metal will remove or displace a less reactive metal from its compound or solution.
The reactivity series for metals is shown lower down this page, it will help you work out what is happening in the equations below. You may notice that two non-metals, carbon and hydrogen have
been included. This is simply because these are common reagents that are reacted with metal compounds, hydrogen and carbon are often used to extract metals from their ores.
Consider the following displacement reaction. A strip of zinc metal is dipped into a copper sulfate solution for about 60 seconds. When the strip of zinc is removed it is covered in a thin layer of black copper powder (note copper is usually a bronze colour but damp copper powder appears black!).
Displacement reactions involving solutions are fun and safe to carry out in the lab. However reactions involving solids are much more violent and much more care is needed to ensure they are carried out safely. The diagram below illustrates the reaction between magnesium powder and copper oxide. Here the more reactive magnesium displaces or removes the less reactive copper from the solid copper oxide. The reaction is violent.
Equations for this reaction are:
In both these examples the more reactive metal is oxidised, it loses electrons and the less reactive metal is reduced, gains electrons. These reactions are displacement reactions but they are also redox reactions.
Hydrogen, though not a metal reacts in many cases as if it was a metal. In terms of reactivity hydrogen sits just above copper in the reactivity series. This means that it can be used to displace any metal below it in the reactivity series such as copper or silver. The image below shows how copper oxide can be reduced to copper using a stream of hydrogen gas from a cylinder.