Question

Part A

Phosgene (carbonyl chloride), COCl2, is an extremely toxic gas that is used in manufacturing certain dyes and plastics. Phosgene can be produced by reacting carbon monoxide and chlorine gas at high temperatures:

CO(g)+Cl2(g)⇌COCl2(g)

Carbon monoxide and chlorine gas are allowed to react in a sealed vessel at 478 ∘C . At equilibrium, the concentrations were measured and the following results obtained:

Gas	Partial Pressure (atm)
CO	0.870
Cl2	1.20
COCl2	0.150

What is the equilibrium constant, Kp, of this reaction?

In Part A, you were given the equilibrium pressures, which could be plugged directly into the formula for K. In Part B however, you will be given initial concentrations and only one equilibrium concentration. You must use this data to find all three equilibrium concentrations before you can apply the formula for K.

Part B

The following reaction was performed in a sealed vessel at 740 ∘C :

H2(g)+I2(g)⇌2HI(g)

Initially, only H2 and I2 were present at concentrations of [H2]=3.20M and  [I2]=2.85M. The equilibrium concentration of I2 is 0.0100 M . What is the equilibrium constant, Kc, for the reaction at this temperature?

Answer 1

Part A

Kp=p(COCl2)/p(CO) *p(Cl2)

Where p=partial pressure of gases

Kp=(0.150 atm) /(0.870 atm)*(1.20 atm)=0.144 atm^-1

Part B

H2(g)+I2(g)⇌2HI(g)

[H2]=3.20M and [I2]=2.85M. The equilibrium concentration of I2 is 0.0100 M .

Change in conc at equilibrium for I2=x=2.85-0.0100=2.84 M

ICE table

	[H2]	[I2]	[HI]
Initial	3.20	2.85	0
change	-2.84	-2.84	+2*2.84=+5.68
equilibrium	3.20-2.84=0.36	2.85-2.84=0.01	5.68

Kc=[HI]^2/[H2] [I2]=(5.68 M)^2/(0.36 M)(0.01 M)=8961.78 (answer)

Kc=8961.78