Taking an example, illustrate a displacement reaction.

The reaction between iron and copper sulphate is a displacement reaction.

Fe(s) + CuSO₄(aq) → FeSO₄(aq) + Cu(s)

Here, iron displaces copper from its solution of copper sulphate.

Illustration: Take two test tubes marked as (A) and (B). Add about 10 ml. copper sulphate in each test tube. Now suspend two clean iron nails in tube (B) with the help of a thread [Fig. 1.2(a)], After 20 minutes, take out the iron nails from tube (B). Compare the intensity of the blue colour of copper sulphate solutions in test tubes (A) and (B) [Fig. 1.2 (b)]. It will be observed

Fig. 1.2. (a) Iron nails dipped in copper sulphate solution (b) Iron nails and copper sulphate solutions compared before (A) and after the experiment (B).

that blue colour of copper sulphate fades in test tube (B) because Cu²⁺ ions are removed from solution which is deposited on iron nails which then appears brownish. This is due to fine deposition of copper on iron nails.