Which of the following pairs will give a displacement reaction?

The correct option is D

${\mathrm{AgNO}}_3$solution and Copper metal

The explanation for the correct answer

(D) ${\mathbf{AgNO}}_{\mathbf{3}}\mathbf{}$solution and Copper metal

Displacement reaction

• The atom or a set of atoms displaced by another atom in a molecule is known as a displacement reaction.
• Less reactive metals in the salts are displaced by more reactive metals.
• A reaction does not take place when a less reactive metal is added to the solution of a more reactive metal.
• Here, $\mathrm{Cu}$is more reactive than$\mathrm{Ag}$. So displacement takes place.
• The reaction is given by
• $$\begin{gathered} \mathrm{Cu}\left(\mathrm{s}\right)+2{\mathrm{AgNO}}_3\left(\mathrm{aq}\right)\to \mathrm{Cu}{\left({\mathrm{NO}}_3\right)}_2\left(\mathrm{aq}\right)+2\mathrm{Ag}\left(\mathrm{s}\right) \\ \left(\mathrm{Copper}\right)(\mathrm{Silver}\mathrm{Nitrate})\left(\mathrm{Copper}\right(\mathrm{II})(\mathrm{Silver}) \\ \mathrm{Nitrate}) \end{gathered}$$
• Here Copper metal oxidized to${\mathrm{Cu}}^{2+}$.
• Silver cation reduced to Silver metal.

Hence, Option (D) ${\mathbf{AgNO}}_{\mathbf{3}}\mathbf{}$solution and Copper metal are correct.

The explanation for the Incorrect Answer
(A) $\mathbf{NaCl}$ solution and copper metal

• $\mathrm{Cu}$metal is less reactive than $\mathrm{Na}$in the salt
• So displacement reaction does not occur.

(B) ${\mathbf{MgCl}}_{\mathbf{2}}$solution and aluminum metal

• $\mathrm{Al}$metal is less reactive than $\mathrm{Mg}$in the salt.
• So displacement reaction does not occur.

(C) ${\mathbf{FeSO}}_{\mathbf{4}}$ solution and silver metal

• $\mathrm{Ag}$metal is less reactive than $\mathrm{Fe}$in the salt
• So displacement reaction does not occur.

Therefore, Option (D) ${\mathbf{AgNO}}_{\mathbf{3}}\mathbf{}$solution and Copper metal are correct.