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### Heterogeneous Equilibria

Posted: Mon Jan 06, 2020 8:33 pm
For a heterogeneous equilibrium, what expression is utilized to find the equilibrium constant?

### Re: Heterogeneous Equilibria

Posted: Mon Jan 06, 2020 9:02 pm
aphung1E wrote:For a heterogeneous equilibrium, what expression is utilized to find the equilibrium constant?

K is always equal to [Products]/[Reactants]. Heterogeneous Equilibria just means that at least one of the components in the reaction, whether it be a reactant or a product, is in a different phase (gas, liquid, solid, aqueous). For Heterogeneous Equilibria, solids and liquids are not included when solving for K.

### Re: Heterogeneous Equilibria

Posted: Mon Jan 06, 2020 9:04 pm
For heterogeneous equilibria, you will use the same general equation to find the equilibrium constant as for homogeneous equilibria: $K_{c}=\frac{[C]^c[D]^d}{[A]^a[B]^b}$. However, in heterogeneous equilibria, you will NOT include any solids or pure liquids in the formula. I believe this is because they don't really affect the concentrations of reactants/products at equilibrium and it doesn't really make sense to talk about the concentration of a pure solid/liquid. You'll only include gases or aqueous solutions.

As an example, if you were given the chemical reaction: $P_{4}S_{10} (s) + 16H_{2}O (l) \rightleftharpoons 4H_{3}PO_{4} (aq) + 10H_{2}S (aq)$, the equation for the equilibrium constant would just be $[H_{3}PO_{4}]^{4} [H_{2}S]^{10}$ because you don't include the solids or liquids in the equation.