Question

Explain with an example how displacement reactions help to distinguish between more reactive and less reactive elements.

Answer 1

• A displacement reaction is the one wherein the atom or a set of atoms is displaced by another atom in a molecule.
• The general representation of this reaction type is
• A + B-C → A-C + B
• When an iron nail is placed in copper sulphate solution iron displaces copper to form ferrous sulphate and copper metal.
• $\underset{\mathrm{Iron}}{\mathrm{Fe}\left(\mathrm{s}\right)}+\underset{\mathrm{Copper}\mathrm{sulphate}}{{\mathrm{CuSO}}_4\left(\mathrm{aq}\right)}\to \underset{\mathrm{Ferrous}\mathrm{sulphate}}{{\mathrm{FeSO}}_4\left(\mathrm{aq}\right)}+\underset{\mathrm{Copper}}{\mathrm{Cu}\left(\mathrm{s}\right)}$
• When we put copper in ferrous sulphate solution we observe no reaction taking place.
• $\underset{\mathrm{Ferrous}\mathrm{sulphate}}{{\mathrm{FeSO}}_4\left(\mathrm{aq}\right)}+\underset{\mathrm{Copper}}{\mathrm{Cu}\left(\mathrm{s}\right)}\to \mathrm{No}\mathrm{reaction}$
• This helps us understand that Iron is more reactive than copper and displaced it, but copper can not displace iron in a ferrous sulphate solution.