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ignoring solids & liquids for K

Posted: Thu Jan 23, 2020 11:12 pm
by 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-?

Re: ignoring solids & liquids for K

Posted: Thu Jan 23, 2020 11:17 pm
by 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.

Re: ignoring solids & liquids for K

Posted: Thu Jan 23, 2020 11:19 pm
by Ryan Yoon 1L
The Calcium Hydroxide is dissolved in water making it an aqueous solution.

Re: ignoring solids & liquids for K

Posted: Tue Mar 17, 2020 12:48 am
by ursulavictorino1K
So an aqueous solution isn't considered a liquid?

Re: ignoring solids & liquids for K

Posted: Tue Mar 17, 2020 6:25 am
by Jiyoon_Hwang_2I
ursulavictorino1K wrote: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.

Re: ignoring solids & liquids for K

Posted: Tue Mar 17, 2020 10:46 pm
by Vuong_2F
ursulavictorino1K wrote: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.

Re: ignoring solids & liquids for K

Posted: Wed Mar 18, 2020 12:10 am
by 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.

Re: ignoring solids & liquids for K

Posted: Wed Mar 18, 2020 12:27 am
by Jeremy_Guiman2E
When ions dissociate in solution, they are considered aqueous and are therefore not considered solids/liquids.