The degree of dissociation of P C l 5 ( g ) for the equilibrium P C l 5 g ⇌ P C l 3 g + C l 2 ( g ) is approximately related to the pressure at equilibrium (P) by the relation [ α ≪ 1 ]

Step-by-step solution

PCl 5 ⇌ PCl 3 + Cl 2 Total pressure = P 1 0 0 1 - α α α ∴ K P = α P 1 + α α 1 + α P 1 - α 1 + α P = α 2 1 - α 2 P ≈ α 2 P α ≪ 1 Neglecting ' α 2 ' K P = α 2 P ∴ α = K P P