[T]

Hello,

How would you find the equilibrium constant of a reaction that contains both gases and aqueous solutions? Or are these reactions impossible? Do you use Kp or Kc or another equation?

Thanks

[Borek]

Actually you can mix pressures and concentrations, for example

CaCO₃(s) + CO₂(g) + H₂O(l) Ca²⁺(aq) + 2HCO₃^-(aq)

has equilibrium constant of

[tex]K = \frac{[Ca^{2+}][HCO_3^-]^2}{P_{CO_2}[H_2O]}[/tex]

(I should add some disclaimers here, but let's not worry about minute details for a moment).

[T]

Hello Borek,

Why did you add H₂O in the equilibrium equation?

Also what are disclaimers?

Thanks

[Borek]

Why did you add H₂O in the equilibrium equation?

Because it is present in the reaction equation. Typically - in water solutions - concentration of water is constant and doesn't change during the reaction, so we can ignore it (it is equivalent of assuming it is just a part of the equilibrium constant). But just because we typically ignore it doesn't mean it is not there.

Also what are disclaimers?

Way above your head. Don't worry about them for now, just be prepared it is not yet a full picture. What you already know should be enough for solving many problems.

Actually I doubt anyone has a full picture.

[T]

Ok, thank you very much Borek

Do you always exclude solids and liquids from the equilibrium constant in a heterogenous reaction fpr both Kp and Kc?

[Borek]

Do you always exclude solids and liquids from the equilibrium constant in a heterogenous reaction fpr both Kp and Kc?

Yes. Technically they are there, we just assume their concentration/activity equals 1.