Question

Which is in favour of forward reaction for reaction
$PC{I}_5\left(g\right)\rightleftharpoons PC{I}_3\left(g\right)+C{I}_2\left(g\right)$ at constant temperature:

• A. Addition of inert gas at constant volume
• B. Addition of $PC{I}_3\left(g\right)$ at constant volume
• C. Addition of $PC{I}_5\left(g\right)$ at constant volume
• D. Addition of $C{I}_2\left(g\right)$ at constant volume

Answer 1

Answer: (A)

Addition of inert gas at constant volume

According to Le chatelier's principle, if a system in equilibrium is disturbed by changes in determining factors, such as temperature, pressure, and concentration of components then the system will tend to shift its equilibrium position in such a way so as to counteract the effect of the disturbance.

At constant volume, there will be an increase in the total pressure of the system but the partial pressure of both the reactants and products remain the same. Hence, there will be no effect on the equilibrium.

At constant pressure, there will be an increase in total volume. Therefore, there will be a decrease in the number of moles per unit volume of each reactant and product. Hence, the equilibrium will shift towards the side where the number of moles is increased.

Thus, we can conclude that introducing inert gas at constant pressure will favor the forward reaction for the given reaction at constant pressure.