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.

Consider the following reaction and associated equilibrium constant:

aA (g) + bB (g) ⇌cC (g), Kc = 4.0

The equation for Kc:

Kc = [C]² / [A] [B]

Let the equilibrium concentration of C be x

Then,

the equilibrium concentration of A = 1-x

the equilibrium concentration of B = 1-x

The equation becomes:

4 = x² / (1 - x) ²

3x² - 8x + 4 = 0

x = 2, x = 2/3

The first answer is not possible so x = 2/3

[A] = 1 - 2/3 = 1/3

[B] = 1 - 2/3 = 1/3