## Reason for not including water

Acidity $K_{a}$
Basicity $K_{b}$
The Conjugate Seesaw $K_{a}\times K_{b}=K_{w}$

Gurvardaan Bal1L
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### Reason for not including water

Do we not include water in the acidity/basicity constants because it is a pure liquid or because it is in excess? I heard both from different people and wanted to know which is correct or if both are correct.

kaushalrao2H
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### Re: Reason for not including water

for K (acid/base) constants, we only use concentrations of aqueous or gaseous substances, and leave out pure substances (solid and liquid).

Nha Dang 2I
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### Re: Reason for not including water

Yeah, you don't include water because it is a liquid. Liquids and solids aren't included in the constants because they don't affect the reactant amount at equilibrium.

JamesAntonios 1E
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### Re: Reason for not including water

Both your reasons that you stated are equally correct. Remember though than in Le Chatelier's Principle, the concentration of everything can be affected by the addition or subtraction of water.

AnuPanneerselvam1H
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### Re: Reason for not including water

Since water is the solvent, it's concentration will barely be affected. Therefore it is not included in the equilibrium ratio.

Jorge Gomez3F
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### Re: Reason for not including water

We do not include water because it present in such a great quantity that the reaction will not change how much there is. Also water is a pure liquid and a solvent therefore it can technically be both.

Matt_Fontila_2L_Chem14B
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### Re: Reason for not including water

Water is the solvent in which the reaction occurs. It's not included in the K expression.