Question

For the reaction below, Kp= 28.09 at 800K. Calculate the equilibrium partial pressure of the reactants and products if the intitial pressure arePpCl5= 0.5300 atm and PpCl3= .5200 atm.

PCl5--> PCl3 + Cl2

PCl5=   

Cl2=

PCl3=

Answer 1

PCl4 --> PCl3 + Cl2, the Kp = 28.61 and is >> 1. so, we know from this that the products are heavily favored in this reaction.

using an ice chart just helps to visualize the changes that occur during the reaction

.............PCl5........PCl3....Cl2
Initial.....0.53..........0.52......0
change..-x...............+x....+x........ is based upon the balanced equation
eq.......0.53-x........0.52+x....x

Kp = [p PCl3][p Cl2] / [p PCl5]
28.09 = (0.52 + x)(x) / (0.53 - x)
28.09 = 0.52x + x^2 / 0.53-x
14.89 - 28.09x = 0.52x + x^2
x^2 + 29.61x - 14.89 = 0
quadratic equation
x = [p Cl2] = 0.495atm
[p PCl5] = 0.53 - 0.495 = 0.035atm
[p PCl3] = 1.015atm