Which of the following reactions is the metal displacement reaction ? Choose the right option.

The correct answer is:
${\mathrm{Cr}}_2{O}_3+2\mathrm{Al}\stackrel{\Delta }{\to }{\mathrm{Al}}_2{O}_3+2\mathrm{Cr}$

Step-by-Step Explanation:

To identify the metal displacement reaction, let us first define what a displacement reaction and a metal displacement reaction are, and then analyze the chemical equations shown in each image.

1. Understanding Metal Displacement Reactions:
A displacement reaction is a chemical reaction in which a more reactive element displaces a less reactive element from its compound.
Specifically, in a metal displacement reaction, a more reactive metal displaces a less reactive metal from its oxide, halide, or other salt solutions. The general form is:
$A+BX\to AX+B$
where metal A is more reactive than metal B, thereby displacing B from its compound BX.

2. Analyzing each option from the provided images:

Option 1 (Image 0):
The equation shown is:
$2K\mathrm{Cl}{O}_3\stackrel{\Delta }{\to }2K\mathrm{Cl}+3O_2$
This is a decomposition reaction (specifically, thermal decomposition) because a single reactant (potassium chlorate) breaks down under heat (indicated by the delta symbol Δ) into two simpler products (potassium chloride and oxygen gas).

Option 2 (Image 1):
The equation shown is:
${\mathrm{Cr}}_2{O}_3+2\mathrm{Al}\stackrel{\Delta }{\to }{\mathrm{Al}}_2{O}_3+2\mathrm{Cr}$
In this reaction, aluminium ($\mathrm{Al}$) is a more reactive metal than chromium ($\mathrm{Cr}$). When heated, the aluminium metal displaces the chromium metal from its oxide (${\mathrm{Cr}}_2{O}_3$), resulting in the formation of aluminium oxide (${\mathrm{Al}}_2{O}_3$) and pure chromium metal. Therefore, this reaction is a classic metal displacement reaction.

Option 3 (Image 2):
The equation shown is:
$\mathrm{Fe}+2H\mathrm{Cl}\to \mathrm{Fe}{\mathrm{Cl}}_2+H_2\uparrow$
Here, iron ($\mathrm{Fe}$) displaces hydrogen ($H$) from hydrochloric acid. Since hydrogen is a non-metal, this is classified as a non-metal displacement reaction (specifically, a hydrogen displacement reaction).

Option 4 (Image 3):
The equation shown is:
$2\mathrm{Pb}{\left(N{O}_3\right)}_2\to 2\mathrm{Pb}O+4N{O}_2+O_2\uparrow$
This is another example of a thermal decomposition reaction, where lead(II) nitrate decomposes into lead(II) oxide, nitrogen dioxide, and oxygen gas.

Conclusion:
Comparing all the choices, the reaction represented in Option 2 (Image 1) is the only metal displacement reaction.