Equilibria chemistry - The Equilibrium Law - Core Idea

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Additional Resources & Activities

Additional resources and activities

Units of Kc

There are no set units for K_c. Each equilibrium must be looked at separately because the units depend on the K_c expression.

Look at the following worked example, which shows how the units of K_c can be worked out for the equilibrium 2SO₂(g) + O₂(g) _∏ 2SO₃(g).

[INSERT CI_03_ani]

Ethanol and ethanoic acid form an equilibrium mixture with the ester ethyl ethanoate and water:

C₂H₅OH(l) + CH₃COOH(l) _∏ CH₃COOC₂H₅(l) + H₂O(l)

$\inline \dpi{100} \large K_\textup{c} = \frac{[\textup{CH}_{3}\textup{COOC}_{2}\textup{H}_{5}][\textup{H}_{2}\textup{O}]}{[\textup{C}_{2}\textup{H}_{5}\textup{OH}][\textup{CH}_{3}\textup{COOH}]}$

What are the units for K_c? Explain your answer.

K _c doesn't have any units because they all cancel out.