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