Question

The conversion of ozone into oxygen is exothermic under what conditions is ozone the most stable?
Option:
(A) At low pressure & low temperature
(B) At high pressure & high temperature
(C) At high pressure & low temperature
(D) At low pressure & high temperature

Answer 1

Hint: Try to write the reaction of ozone converting to oxygen & use the concept of Le-chateler’s principle to predict under what conditions ozone will be more stable

Complete solution:
First, we will write the reaction of how ozone converts into oxygen.

Reaction: ${20}_3\rightleftharpoons {30}_2$

$\Rightarrow$ 2 moles of ozone will convert into 3 moles of oxygen.

Now, here we will use the concept of le- chateler’s principle to determine at what conditions ozone will be stated.
Here, we want the reaction to proceed in a backward direction i.e. towards formation of ozone. i.e. a side where it has fewer moles.
Now, Le- chateler’s principle states that when a pressure increases during a reaction shifts to that direction with fewer numbers of moles.
Hence, ozone has 2 moles & ${\text{O}}_{\text{2}}$ has 3 moles. So, an increase of pressure will be favourable for the formation and stability of ozone.
Now, talking about the temperature, this reaction ${20}_3\rightleftharpoons {30}_2$is an exothermic reaction i.e. heat is released.
Which implies ${20}_3\rightleftharpoons {30}_2$ will definitely be a endothermic reaction, Now, according to Le-chatelier’s principle, increase of temperature will cause the equilibrium to shift to from the endothermic reaction.
Therefore high temperatures are favourable for the stability of ozone.
High temperature & high pressures one suitable for use stability of ozone

Correct option (B) High temperature & high pressure.

Note: Ozone can also be prepared in the laboratory in two ways: corona discharge & UV ozone generators. Ozone layers are very important to us as it helps save us from harmful UV rays coming from the sun.