Question

In a vessel containing ${SO}_3,{SO}_2$ and $O_2$ at equilibrium, some helium gas is introduced so that total pressure increases while temperature and volume remain the same. According to Le Chatelier's principle, the dissociation of ${SO}_3$:

• A. increases
• B. decreases
• C. remains unalered
• D. changes unpredictably

Answer 1

Answer: (C)

remains unalered

The given reaction is :-

$2{SO}_{3\left(g\right)}\rightleftharpoons 2{SO}_{2\left(g\right)}+O_{2\left(g\right)}$

In this reaction at equation, keeping temperature and volume constant, Helium gas is introduced so that total pressure is increased. The forward reaction is accompanied by increase in no. of moles, so, if pressure is increased, then as per Le Chatelier's principle, equilibrium shift in the direction of decreasing no. of moles. So, dissociation of ${SO}_3$ is decreased.