Liquids not used in Kc

[Samantha Chung 4I]

During class today, a pure substance is not used in Kc, when I watched the video modules, an example was given with a dilute solution. But if the liquid is a concentrated substance, will that change anything?

[Mona Lee 4L]

No. In a Kc expression, you do not need to include the solute. The change in the concentration of any solute will be insignificant.

[gwynlu1L]

I believe you meant solvent. In the equilibrium constant, pure substances such as solids, solvents, or pure liquids are omitted bc their concentrations do not change significantly. Since pure water is usually the solvent used in many reactions, you omit putting pure liquid H2O into the equilibrium constant. If (aq) is next to a substance in a chemical equation, it is only a solution and not pure, so you do include it in the equilibrium constant.