Question

When lead powder is added to copper chloride solution, a displacement reaction occurs and solid copper is formed.
i) Write the equation for the reaction
ii) Why does the displacement reaction occur?

Answer 1

Hint: We know that chemical reactions are those changes in which new substances form which possess completely different physical and chemical properties than the reactants. There are four types of chemical reaction, decomposition reaction, combination reaction displacement reaction and double displacement reaction.

Complete step by step answer:
Let’s discuss reactivity or activity series of metals in detail. . Activity series of metals is a list of metals arranged according to their reactivity. The highly reactive metal displaces less reactive metal in displacement reaction. As potassium is the highest reactive metal it can displace all other metal atoms from their compounds.

(Image drawn by SME)


Let’s discuss the displacement reaction in detail. A reaction where displacement of a less reactive metal from its compound occurs by a more reactive metal is termed as displacement reaction.
An example of displacement reaction is,
\[{\rm{Fe}} + {\rm{CuS}}{{\rm{O}}_{\rm{4}}} \to {\rm{FeS}}{{\rm{O}}_{\rm{4}}} + {\rm{Cu}}\]
As reactivity of iron is more than copper, so it displaces copper from copper sulphate.

(i) Here, the reactants are given as lead and copper chloride. To undergo a displacement reaction, the reactivity of lead must be more than copper. And from the reactivity series of metals, we can see that lead is above copper. So, reactivity of lead is more than copper.
So, the displacement reaction is,
${\rm{Pb}} + {\rm{CuC}}{{\rm{l}}_2} \to {\rm{PbC}}{{\rm{l}}_{\rm{2}}} + {\rm{Cu}}$


(ii) The displacement reaction occurs between lead and copper chloride because reactivity of lead is more than copper. So, displacement of copper by lead takes place.

So, the correct answer is Option A.

Note: In a double displacement reaction, the exchange of ions of two ionic compounds takes place. The reaction between potassium nitrate and aluminium chloride represents a double displacement reaction.

\[{\rm{KN}}{{\rm{O}}_{\rm{3}}} + {\rm{AlC}}{{\rm{l}}_{\rm{3}}} \to {\rm{Al}}{\left( {{\rm{N}}{{\rm{O}}_{\rm{3}}}} \right)_3} + {\rm{KCl}}\]