A. Carbonyl fluoride, COF2, is an important intermediate used in the production

Question

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=8.60

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

B.Consider the reaction

CO(g)+NH3(g)HCONH2(g),    Kc=0.900

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

A. 2 COF2 <=> CO2 + CF4
2.00 -2x <=> x & x

K = [CO2] [CF4] / [COF2)2

8.60 = [x] [x] / [2 - 2x]2  

8.60 [2 - 2x]2 = [x]2

8.60 [4 - 8x +4x2] = [x]2

33.4x2 - 68.8x + 34.4 = 0

x = 0.85 and 1.2 { 2x < 2.0 M , 1.2 is not possible so 0.85 is x}

what concentration of COF2 remains at equilibrium:
2.00 - 2x = 0.30 M

B. Kc = [HCONH2] / [CO][NH3]
let X = moles/L of HCONH2 formed
[CO] = 1.00 M - X
[NH3] = 2.00 M - X
[HCONH2] = X
0.90 = [X] / [1.00-X] [2.00-X] = [X ] / 2.00 - 3.00 X + X2
0.90X2 - 3.7X + 1.80 = 0
X = 0.56 and 3.54 { x < 1,2 so x = 0.56}
HCONH2 = 0.56 M

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