For the following endothermic reactions: `PCl_(5)hArrPCl_(3)(g)+Cl_(2)(g)` (a) At constant temperature, what will be the effect of pressure? (b) At constant volume, what will be the effect of addition of chlorine gas and nitrogen gas on the position of equilibrium?

Explanation

(a) In the given reversible reaction, the number of gas molecules increses in the forward direction, while it decreases in the reverse direction. So, according to Le Chatelier's principle, at constant temperature, the increase in pressure will shift the equilibrium to the left and decrease in pressure will shift the equilibrium to the right.
(b) AT constant temperature and volume, adding `Cl_(2)(g)` [one of the products] to the reaction system at equilibrium increases the concentration of `Cl_(2)(g)` , thereby causing the equilibrium to shift to the lift.
At constant temperature and volume, adding `N_(2)(g)` [an inert gas] to the reaction systemm at equilibrium does not affect the position of the equilibrium. this is because addition of `N_(2)(g)` although increases the total pressure of the reaction system. it causes no change in the partial pressures of `PCl_(5)(g),PCl_(3)(g) and Cl_(2)(g)`.