Equilibria chemistry - Gaseous equilibria - Core Idea

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Kp and heterogeneous equilibria

[INSERT GE_CI_05_ima]

Several important equilibria involve both gases and solids. These are examples of heterogeneous equilibria because some of the reactants and products are in dfifferent physical states. Just as in the case of K_c, when writing expressions for K_p for heterogeneous equilibria we don't include a term for the solid.

So for the equilibrium H₂O(g) + C(s) _∏ H₂(g) + CO(g):

$\inline \dpi{100} \large K_{\textup{p}}= \frac{(P_{\textup{H}_{2}})(P_{\textup{CO}})}{(P_{\textup{H}_{2}\textup{O}})}$

What would be the expression for K_p for the equilibrium 2NaHCO₃(s) _∏ Na₂CO₃(s) + CO₂(g) + H₂O(g)?

$\inline \dpi{100} \large K_{\textup{p}}= (P_{\textup{CO}_{2}})(P_{\textup{H}_{2}_}_{\textup{O}})$

What would be the expression for K_p for the equilibrium CaO(s) + CO₂(g) _∏ CaCO₃(s)?

$\dpi{100} \large K_{\textup{p}}= \frac{1}{(P_{\textup{CO}_{2}})}$