In: Chemistry
At a particular temperature the equilibrium constant for the
reaction:
H2(g) + F2(g) ⇔ 2HF(g)
is K = 64.0. A reaction mixture in a 10.00-L flask contains 0.23
moles each of hydrogen and fluorine gases plus 0.50 moles of HF.
What will be the concentration of H2 when this mixture
reaches equilibrium?
Equilibrium Quotient expression is
Qc = [HF]^2/[H2]*[F2]
= (0.05^2)/(0.023^1)*(0.023^1)
=4.73
comparing Q and k
since Q is lesser than K
reaction will move in forward direction
ICE Table:
[H2]
[F2]
[HF]
initial
0.023
0.023
0.05
change -1x -1x +2x
equilibrium 0.023-1x 0.023-1x 0.05+2x
Equilibrium constant expression is
Kc = [HF]^2/[H2]*[F2]
64.0 = (0.05 + 2*x)^2/(0.023-1*x)^2
sqrt(64.0) = (0.05 + 2*x)/(0.023-1*x)
8.0 = (0.05 + 2*x)/(0.023-1*x)
0.184-8*x = 0.05 + 2*x
0.134-10*x = 0
x = 0.0134
At equilibrium:
[H2] = 0.023-1x = 0.023-1*0.0134 = 0.0096 M
Answer: 0.0096 M