Question

Carbonyl fluoride, COF2, is an important intermediate used in the production of fluorine-containing compounds. For instance, it is used to make the refrigerant carbon tetrafluoride, CF4 via the reaction 2COF2(g)⇌CO2(g)+CF4(g), K=7.80 at 850 K If only COF2 is present initially at a pressure of 240 kPa, what is the partial pressure of COF2 at equilibrium? You can convert the units of pressure from kPa to bar, using the relation 1 kPa=0.01 bar. Express your answer with the appropriate units.

Answer 1

2COF2(g)⇌CO2(g)+CF4(g) K = 7.80

Intial partial pressure of COF2 = 240 kPa = 240 x 0.01 bar = 2.4 bar

2COF2(g) ⇌ CO2(g) + CF4(g)

Initial partial pressure 2.4 bar 0 0

Equilibrium partial pressure 2.4-2X X X

Hence, Equilibrium partial pressures are

P_COF2 = 2.4-2X

P_CO2 = X

P_CF4 = X

K = P_CO2 . P_CF4 / P²C_OF2

7.8 = X.X / (2.4-2X)²

44.93 + 31.2 X²- 74.88 X =  X²

30.2 X²- 74.88 X + 44.93 = 0

On solving, X = 1.02 bar

Hence,

Partial pressure of COF2 at equilibrium = 2.4 - 2X = 2.4 - (2x1.02) = 0.36 bar

Therefore,

partial pressure of COF2 at equilibrium = 0.36 bar