PCl5(g) <-----> PCl3(g) + Cl2(g) initial pressure .. 0.48 <-----> 0 + 0 at equilibrium pressure will be .. (0.48-x) <-----> x + x
given total pressure = 0.806 so partial pressure of PCl5 + partial pressure of PCl3 + partial pressure of Cl2 = 0.806 (0.48-x) + x + x = 0.806 0.48 + x = 0.806 x = 0.806-0.48 = 0.326
so at equilibrium partial pressure of PCl5 = 0.48-x = 0.48-0.326 = 0.154 atm partial pressure of Cl2 = x = 0.326 atm partial pressure of PCl3 = x = 0.326 atm so Kp = P(PCl3) X P(Cl2)/P(PCl5) = 0.326 X 0.326/0.154 = 0.690