The pressure at which equilibrium constant in term of pressure is found to be equal to that in terms of mole fraction for the equilibrium, 

${\mathrm{PCl}}_{5\left(g\right)}\rightleftharpoons {\mathrm{PCl}}_{3\left(g\right)}+{\mathrm{Cl}}_{2\left(g\right)}\text{ is : }$