Part A Carbonyl fluoride, COF2, is an important intermediate used in the product

Question

Part A

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),    Kc=8.20

If only COF2 is present initially at a concentration of 2.00 M, what concentration of COF2 remains at equilibrium?

Part B

Consider the reaction

CO(g)+NH3(g)?HCONH2(g),    Kc=0.790

If a reaction vessel initially contains only CO and NH3 at concentrations of 1.00 M and 2.00 M, respectively, what will the concentration of HCONH2 be at equilibrium?

Explanation / Answer

2COF2(g)?CO2(g)+CF4(g)

At t = 0

[COF2] = 2 , [CO2] = 0 , [CF4]=0

at t = t at equillibrium

[COF2] = 2 - 2x , [CO2] = x , [CF4]=x

Kc = (x * x) / (2-2x)2

8.20 = x^2 / (4 + 4x^2 -8x)

x^2 = 32.8 x^2 - 65.6 x + 32.8

31.8 x^2 -65.6x + 32.8 = 0

Solving this quadratic equation for x, we get

x = 1.212 or x =0.851

So,

[COF2] at equillibrium = 2 - 2x = 2 - 2 * 0.851 = 0.298 M (x = 1.212 ignored as [COF2] will become negative)

B)

Kc = [HCONH2] / [CO] * [NH3]

0.790 =  [HCONH2] / 1 * 2

[HCONH2] = 2 * 0.790 = 1.58 M

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