Displacement Reaction

What is Displacement Reaction?

Reaction in which a more reactive element takes the place of a less reactive element in a chemical compound is called Displacement Reaction.

Example 1

When a piece of iron nail is placed in blue colored copper sulphate solution , iron sulphate and copper is formed as shown below

Fe(s) + CuSO ₄ (aq) → FeSO ₄ (aq) + Cu(s)

In this case, 

• Blue colored copper sulphate solution fades because of formation of colorless iron sulphate solution.
• Brownish red color of copper takes place on iron nail

Reason

In this reaction, iron displaces copper from copper sulphate solution

This displacement Reaction occurs because iron is more reactive than copper.

How to determine which element will replace and which will not?

This  is determined by the reactivity series .

It is a series of elements arranged in decreasing order of reactivity.

(Most reactive on top, least reactive on bottom)

The reactivity series is as follows

It can be memorized as, 

“Please Send Berries, Carrots, Mangoes All Zipped IN The Large Handbag”, Charlie MSG-ed (Messaged) Paul

Example 2

When a piece of Zinc (Zn) is placed in blue colored Copper Sulphate (CuSO 4 ) solution

Zinc Sulphate and Copper is formed as shown below,

Zn(s) + CuSO ₄ (aq)  → ZnSO ₄ (aq) + Cu(s)

Zinc is more reactive than copper

(It lies above copper in the reactivity series)

As a result, Zinc displaces copper from its solution

Thus forming, Zinc Sulphate and Copper

Example 3

When a piece of Lead (Pb) is placed in Copper Chloride (CuCl 2 ) solution

Lead Chloride and Copper is formed as shown below,

Pb(s) + CuCl 2 (aq) → PbCl 2 (aq) + Cu(s)

Lead is more reactive than Copper

(It lies above Copper in the reactivity series)

As a result, Lead displaces Copper from its solution

Thus forming, Lead Sulphate and Copper

Note - If a less reactive metal is made to react with a compound containing more reactive metal, then the displacement reaction does not take place. 

Example 1 : Cu(s) + FeSO ₄ (aq) → No reaction

Reaction does not take place as Cu lies below Fe in the reactivity series

Example 2 : Cu(s) + PbCl ₂ (aq) → No reaction

Reaction does not take place as Cu lies below Pb in the reactivity series

Intext Question - Page 13 Q1

NCERT Exercise - Q2, Q3, Q14