For the reaction : PCl 5 g ⇌ PCl 3 g +Cl 2 g . The forward reaction at constant temperature is favoured by

Step-by-step solution

PCl 5 g ⇌ PCl 3 g + Cl 2 g mole at equilibrium a − x x x K C = x 2 a - x V Addition inert gas at constant V has no effect on reactions having Δ n = 0 or Δ n ≠ 0 . But addition of inert gas at constant P has effect on reactions having Δ n ≠ 0 ; and no effect if Δ n = 0 . The given reaction has Δ n ≠ 0 : on addition of inert gas at constant P, volume increases. To have K C constant, x must increase.