How do you find the equilibrium constant?

Question

CH3COOCH3(g) + H2O(g) <--> CH3COOH(g) + CH3OH(g)

You prepared a mixture with [CH3COOCH3]initial = 0.2318M and [H2O]initial =0.1952M.

After reaction reaches equilibrium, [CH3COOCH3]equilibrium = 0.0512M. What is the value of the equilibrium constant for this reaction under these conditions?

Answer 1

Set up an ICE table

CH3COOCH3(g) + H2O(g) <--> CH3COOH(g) + CH3OH(g)

0.2318....................0.1952..................0...................0..............Initial

-x............................-x......................+x....................+x.............Change

0.2318-x...............0.1952-x................x......................x.............Equilibrium

0.2318-x = 0.0512

x = 0.1806

Final Concentrations @ Equilibrium

[CH3COOCH3] = 0.0512 M

[H2O] = 0.1952 - 0.0512 = 0.144 M

[CH3COOH] = 0.1806 M

[CH3OH] = 0.1806 M

Writing the Keq expression, we have...

K = [CH3COOH][CH3OH] / [CH3COOCH3][H2O] ... note that [H2O] is included as it is a gas not a liquid

K = (0.1806)(0.1806) / (0.0512)(0.144)

K = 4.42