What is a displacement reaction? Explain the statement 'iron can displace copper from its salt solution, but copper cannot displace iron from its salt solution.'

Displacement reaction is a reaction in which one element displaces another element from its compound and takes its place there in.

It can be represented generically as:

A + B-C → A-C + B

This will most often occur if A is more reactive than B.

The following chemical reaction takes place iron reacts with copper sulphate:

In this reaction, iron is more reactive than copper. Hence it displaces copper from its sulphate and forms a new compound i.e., ferrous sulphate.

The following equation when copper reacts with iron sulphate:

Cu + FeSO₄→ FeSO₄ + Cu

In this reaction, copper is less reactive than iron. Hence it is not able to displace the iron from its sulphate and as a result, gives no reaction.