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Excluding H2O from Ka and Kb

Posted: Sat Jan 25, 2020 6:44 pm
by J Medina 2I
I know we don't include H2O (l) in caluclations for Kb and Ka but why is that?

Re: Excluding H2O from Ka and Kb

Posted: Sat Jan 25, 2020 6:46 pm
by Elena Bell 1C
H2O is typically used as a solvent in its liquid form, so the concentration does not change much before and after the reaction occurs. Since it mostly stays the same, it would not have an affect on the rate of the reaction.

Re: Excluding H2O from Ka and Kb

Posted: Sat Jan 25, 2020 6:49 pm
by Kayla Maldonado 1C
Water is a pure liquid and has an activity equal to 1, therefore, it does not affect the equilibrium constant.

Re: Excluding H2O from Ka and Kb

Posted: Sat Jan 25, 2020 6:57 pm
by Anika Chakrabarti 1A
When H2O is a solvent it is in so much excess that its concentration doesn't change.

Re: Excluding H2O from Ka and Kb

Posted: Sat Jan 25, 2020 7:14 pm
by rabiasumar2E
Solids and liquids don't affect the value of K, therefore we don't include them in the calculations!

Re: Excluding H2O from Ka and Kb

Posted: Sat Jan 25, 2020 7:16 pm
by Max Madrzyk Dis 4G
We don't include H2O (l) in our calculations of Ka and Kb because water is going to be present in so much excess in both the reactants and the products that if we plugged it into the equation the two numbers would just cancel each other out.