When she introduced CO(g) and Cl2(g) into a 1.00 L evacuated container, so that the initial partial pressure of CO was 1.86 atm and the initial partial pressure of Cl2 was 1.27 atm, she found that the equilibrium partial pressure of COCl2 was 0.823 atm. Calculate the equilibrium constant, Kp, she obtained for this reaction.

Kp is 0.00177

Explanation:

We state the equilibrium:

CO(g) + Cl₂(g)  ⇆  COCl₂(g)

Initially we have these partial pressures

1.86 atm for CO and 1.27 for chlorine.

During the reaction, x pressure has been converted. As we have 0.823 atm as final pressure in the equilibrium for COCl₂, pressure at equilibrium for CO and chlorine will be:

1.86 - x for CO and 1.27 - x for Cl₂.

And x is the pressure generated for the product, because initially we don't have anything from it. So pressure in equilibrium for the reactants will be:

1.86 - 0.823 = 1.037 atm for CO

1.27 - 0.823 = 0.447 atm for Cl₂

Let's make, expression for Kp:

Partial pressure in eq. for  COCl₂ / P. pressure in eq. for CO . P pressure in eq. for Cl₂

Kp = 0.823 / (1.037 .  0.447) → 0.00177