Phosphorus pentachloride dissociates as follows, in a closed...

Phosphorus pentachloride dissociates as follows, in a closed reaction vessel, $\mathrm{PCl}_5(\mathrm{~g}) \rightleftharpoons \mathrm{PCl}_3(\mathrm{~g})+\mathrm{Cl}_2(\mathrm{~g})$ If total pressure at equilibrium of the reaction mixture is $\mathrm{P}$ and degree of dissociation of $\mathrm{PCl}_5$ is $\mathrm{x}$, the partial pressure of $\mathrm{PCl}_3$ will be