Displacement Reaction

Activity

1. Take three iron nails and clean them by rubbing with sand paper.
2. Take two test tubes marked as (A) and (B). In each test tube, take about 10 mL copper sulphate solution.
3. Tie two iron nails with a thread and immerse them carefully in the copper sulphate solution in test tube B for about 20 minutes [Fig. 1.8 (a)]. Keep one iron nail aside for comparison.
4. After 20 minutes, take out the iron nails from the copper sulphate solution.
5. Compare the intensity of the blue colour of copper sulphate solutions in test tubes and (B), [Fig. 1.8 (b)].
6. Also, compare the colour of the iron nails dipped in the copper sulphate solution with the one kept aside [Fig. 1.8 (b)].

 

Figure

(a) Iron nails dipped in copper sulphate solution

Figure (b) Iron nails and copper sulphate solutions compared before and after the experiment

Why does the iron nail become brownish in colour and the blue colour of copper sulphate solution fade?

The following chemical reaction takes place in this Activity–

In this reaction, iron has displaced or removed another element, copper, from copper sulphate solution. This reaction is known as displacement reaction.

Other examples of displacement reactions are

Zinc and lead are more reactive elements than copper. They displace copper from its compounds.