Ka of water defined with liquid water in the denominator?

[thebillsfan]

I believe this is the case, but i dont understand why considering liquid usually isnt included in equilibrium constants.

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[ratatat]

According to this, it doesn't include H2O. http://www.chemistry.adelaide.edu.au/external/soc-rel/content/equilibr.htm

"For the example of water, H2O

H+ + OH-, the equilibrium constant is:

[H+] [OH-]
Keq = ----------
[H2O] The concentration of water in a water solution is constant and this expression simplifies to:
Kw = (55.56 M)*Keq = [H+] [OH-]"

Maybe the thing you read forgot to simplify?

 

[thebillsfan]

it was from ek 1001 questions in chem. the question was what's the pKa of pure water. It took the pKw, 10^-14, and divided it by 55.6, the conc of water in pure water.

 

[RogueUnicorn]

Ka of pure water is 10^-7

 

[thebillsfan]

Ka of pure water is 10^-7

wow, then that's a MAJOR error on EKs part. they made it several times. alright im seriously getting off this site now =)