Question

Consider the following reaction and associated equilibrium constant:
aA(g)+bB(g)⇌cC(g), Kc = 5.0

Part A. Find the equilibrium concentrations of A, B, and C for a=1, b=1, and c=2. Assume that the initial concentrations of A and B are each 1.0 M and that no product is present at the beginning of the reaction.

Part B. Find the equilibrium concentrations of A, B, and C for a=1, b=1, and c=1. Assume that the initial concentrations of A and B are each 1.0 M and that no product is present at the beginning of the reaction.

Answer 1

A(g) + B(g) <--------------> 2 C(g)

1.0       1.0                             0

1-x        1-x                              2x

Kc = (2x)^2 / (1-x)^2

5 = (2x)^2 / (1-x)^2

x = 0.528

equilibrium concentrations

[A] = 1 - x = 0.472 M

[B] = 0.472 M

[C] = 1.056 M

Part B :

A(g) + B(g) <-------------->   C(g)

1.0       1.0                             0

1-x        1-x                              x

Kc = (x)^2 / (1-x)^2

5 = (x)^2 / (1-x)^2

x = 0.691

equilibrium concentrations

[A] = 1 - x = 0.309 M

[B] = 0.309 M

[C] = 0.691 M