Question

In a vessel containing $S{O}_3\left(g\right),S{O}_2\left(g\right)$ and $O_2\left(g\right)$ at equilibrium, some helium gas is introduced so that the total pressure increases while temperature and volume remain constant. According to Le Chatelier principle the dissociation of $S{O}_3$.

• A. Increases
• B. Decreases
• C. Remains unaltered
• D. Changes unpredictably

Answer 1

The correct option is C Remains unaltered

The equilibrium inside the vessel will be:
$S{O}_3\left(g\right)\rightleftharpoons S{O}_2\left(g\right)+\frac{1}{2}{O}_2\left(g\right)$
Now inert gas is added to this system at constant volume.
Addition of an inert gas at constant volume to the equilibrium mixture does not affect the position. When an inert gas is added to the equilibrium system at constant volume, then the total pressure will increase. But the concentration of reactants and products (ratio of their moles to the volume of the container) will not change. Hence, the position of the equilibrium will be unaffected.