Question

A.) The reversible chemical reaction A+B⇌C+D has the following equilibrium constant: Kc=[C][D][A][B]=3.9 Initially, only A and B are present, each at 2.00 M. What is the final concentration of A once equilibrium is reached? Express your answer to two significant figures and include the appropriate units.

B.)What is the final concentration of D at equilibrium if the initial concentrations are [A] = 1.00 M and [B] = 2.00 M ? Express your answer to two significant figures and include the appropriate units.

Answer 1

ICE Table:

[A] [B] [C] [D]

initial 2.0 2.0 0 0

change -1x -1x +1x +1x

equilibrium 2.0-1x 2.0-1x +1x +1x

Equilibrium constant expression is

Kc = [C]*[D]/[A]*[B]

3.9 = (1*x)^2/(2-1*x)^2

sqrt(3.9) = (1*x)/(2-1*x)

1.9748417658131499 = (1*x)/(2-1*x)

3.95-1.975*x = 1*x

3.95-2.975*x = 0

x = 1.3277

At equilibrium:

[A] = 2.0-1x = 2.0-1*1.3277 = 0.6723 M

[B] = 2.0-1x = 2.0-1*1.3277 = 0.6723 M

[C] = +1x = +1*1.3277 = 1.3277 M

[D] = +1x = +1*1.3277 = 1.3277 M

A)

0.67 M

B)

1.3 M