`PCl_(5) (g) hArr PCl_(3) (g) + Cl_(2) (g)` - What effects on equilibrium of the reaction will be observed when (a) chlorine gas and (b) nitrogen gas are added separately at constant pressure and constant volume at equilibrium at a constant temperature ?

Explanation

If `Cl_2` gas is added to the reaction system at equilibrium, keeping temperature and pressure constant, the parital pressure of `Cl_(2)` gas is the mixture will increase, thereby making the equilibrium of the reaction disturbed. Accroding to Le Chatelier's principle, the reaction system responds to this distrubance by causing the net reaction to proceed in the reverse directoin os that some of the added `Cl_(2)` gas is consumed in the reaction with `PCl_(3)` gas and the effect of the increase in the partial pressure of `Cl_(2)` is offset. As a result , the equilibrium position of the reaction shifts to the left.
If `Cl_(2)` gas is added to the reaciton system at equilibrium , keeping temperature and volume constant, the concentration of `Cl_(2)` gas in the mixture held increase, thereby making the equlilbrium of the reaction disturbed. According to Le Chatelier's principle , the reaction system responds to this disturbance by causing the reverse reaction to occur to a greater extent so that the effect of the increase in the concentration of `Cl_(2)` is nullified. This results in shifting of the equilibrium position to the left.