ignoring solids & liquids for K

[ursulavictorino1K]

If we are supposed to ignore solids and liquids when calculating K, why is it that in the example CaOH2(s) -> Ca2+(aq) + 2OH-(aq), we used the Ca2+ and OH-?

[Tauhid Islam- 1H]

I think it's because they are dissociated ions in the solution, and not solids or liquids. They are in an aqueous state meaning that the solid dissolved in the solvent (water i believe) and now exists as ions in the solvent.

[Ryan Yoon 1L]

The Calcium Hydroxide is dissolved in water making it an aqueous solution.

[ursulavictorino1K]

So an aqueous solution isn't considered a liquid?

[Jiyoon_Hwang_2I]

So an aqueous solution isn't considered a liquid?

No, only pure liquids (l) and solids (s) are exempt from calculating k. Aqueous solutions describe a solution or mixture containing a solute dissolved in a solvent which is water.

[Vuong_2F]

So an aqueous solution isn't considered a liquid?

Yes, they are different. To sum it up, you would omit a species from the equilibrium expression if it's in a solid(s) or pure liquid (l) state. If they are in an aqueous (aq) or gas (g) state, then you would include the species in the equilibrium expression.

[Gurmukhi Bevli 4G]

Since the Ca(OH)2 gets dissolved in water, it is an aqueous solution, which makes it included within the equilibrium constant calculation.

[Jeremy_Guiman2E]

When ions dissociate in solution, they are considered aqueous and are therefore not considered solids/liquids.