In the following system, PCl5(g) PCl3(g) + Cl2(g) at equilibrium, upon addition of xenon gas at constant T & p, the concentration of
- PCl5, PCl3 & Cl2 remain constant
- PCl3 will increase
- Cl2 will decrease
- PCl5 will increase
Answer
(2) PCl3 will increase
Solution
Xenon is an inert gas. At constant T and p, adding it increases the total volume of the mixture.
Partial pressure of each reacting gas falls: pi = xi p and every mole fraction xi decreases.
Qp = pPCl3 pCl2pPCl5 = nPCl3 nCl2nPCl5 pntotal
ntotal increases Qp < Kp
By Le Chatelier's principle the equilibrium shifts in the forward direction, towards more gaseous moles ( ng = +1).
More PCl5 dissociates; PCl3 (and Cl2) are formed, so PCl3 will increase.
Answer: (2)