Question

For the reaction PC15(9) =PC13(g) + Cl2(g), the forward
reaction at constant temperature is favoured by
(a) introducing an inert gas at constant volume
(b) introducing Cl2 at constant volume
(c) introducing PC15 at constant volume
(d) reducing the volume of the container.​

Answer 1

Introducing an inert gas at constant pressure

• 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 increase in 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 equilibrium.

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

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