A mixture of 10 moles of A, 5 moles of B and 15 moles of C is placed in a one liter container at a constant temperature. The reaction is allowed to reach equilibrium. At equilibrium the number of moles of B is 9. Calculate the equilibrium constant for the reaction.

Equilibrium constant is 0.0873

Explanation:

For the reaction:

A + B ⇄ C

Equilibrium constant is defined as:

K = [C] / [A] [B]

concentrations in equilibrium of each reactant are:

[A] = 10 - X

[B] = 5 - X

[C] = 15 + X

If concentration in equilibrium of B is 9, X is:

[B] = 5 - X = 9 → X = - 4

Replacing:

[A] = 10 - (-4) = 14

[B] = 5 - (-4) = 9

[C] = 15 + (-4) = 11

K = 11 / (14*9) = 0.0873

Thus, equilibrium constant is 0.0873