K for Heterogeneous Equilibria

[Sarah Zhari 1D]

For heterogeneous equilibrium equations where there are both gases and aqueous products or reactants, would you write the equilibrium constant in terms of Kp or Kc?

[Kaitlyn Ang 1J]

Most of the time, if you’re dealing with aqueous solutions, you use Kc. Also, a lot of time, the problems just have K without the subscript c or p, so if you want to be safe, you can just solve for K.

[Naji Sarsam 1F]

For heterogeneous equilibrium problems, it may be confusing as to use either concentrations or pressure. But recognize, if there are any reactants which are aqueous, it does not make sense to use their partial pressure. Thus, you’d have to use concentration for all reagents in the equilibrium. If they give you the partial pressure of a gas, you can use PV=nRT to solve for the molarity.

[CosetteBackus_4F]

For heterogeneous substances, if there are aqueous reactants or products, it makes the most sense to use Kc, since Kp is just for gases.

[Charysa Santos 4G]

Kp is more particular to gases, and Kc applies to when concentrations are being used, so it would probably be safer to use Kc or just to leave K as is. I’m not completely sure, though...