Here 4 moles of inert gas argon also present. ∴ Total moles of mixture present at equilibrium, nT=5+x+4 =9+x At equilibrium, total pressure (pT)=6atm Volume (v)=100L Temperature =610K ∴ using ideal gas equation, PTV=nTRT ⇒6×100=(9+x)×0.082×610 ⇒x=3 Now, KP=
PPCl3×PCl2
PPCl5
=
[
3
9+3
×6]×[
3
9+3
×6]
[
5
9+3
×6]
=
27
12
=
9
4
=2.25atm Note : Inert gas always contribute to total mole and pressure calculation.