Chemists studied the formation of phosgene by sealing 0.96 atm of carbon monoxide and 1.15 atm of chlorine in a reactor at a certain temperature. The pressure dropped smoothly to 1.47 atm as the system reached equilbrium. Calculate Kp (in atm-1) for CO(g) + Cl2(g) ↔ COCl2(g)

3.9

Explanation:

Let's consider the following reaction at equilibrium.

CO(g) + Cl₂(g) ↔ COCl₂(g)

We can find the pressures at equilibrium using an ICE chart.

       CO(g) + Cl₂(g) ↔ COCl₂(g)

I       0.96       1.15            0

C        -x           -x            +x

E    0.96-x    1.15-x           x

The sum of the partial pressures is equal to the total pressure.

pCO + pCl₂ + pCOCl₂ = 1.47

(0.96-x) + (1.15-x) + x = 1.47

2.11 - x = 1.47

x = 0.64

The pressures at equilibrium are:

pCO = 0.96 - x = 0.32 atm

pCl₂ = 1.15 - x = 0.51 atm

pCOCl₂ = x = 0.64 atm

The pressure equilibrium constant (Kp) is:

Kp = pCOCl₂ / pCO × pCl₂

Kp = 0.64 / 0.32 × 0.51

Kp = 3.9