hot to calculate pKw

I know how to calculate pKa for a weak acid,eg CH3COOH. it's the pH when [CH3COO]= [CH3COOH], half way to the straight part of the titration curve.(not half way in the straight part of the curve) but what about pKw, is it the pH for the [H] when Kw =[OH], or is it just the pH, that is the pH for the [H] when [H]= Kw/[OH]. which one is it? by analogy i think it is that when Kw =[OH]?

Reply 1

mackin boi

isnt it always 14

Reply 2

TerrorSquad

i thinks pkW = 14 - pOH??

not too sure tough

Reply 3

corkskrew

pKw is -log of Kw....? Kw is always 1x10^-14 at RTP

Reply 4

mackin boi

so it is 14 yea...pKw = pH + pOH

Reply 5

mackin boi

TerrorSquad

i thinks pkW = 14 - pOH??

not too sure tough

thats pH uve calculated there :biggrin:

Reply 6

corkskrew

mackin boi

so it is 14 yea...pKw = pH + pOH

Kw = [H+] * [OH-]

So to find pH (of a base of known conc)....

[H+] = Kw / [OH-]

Then pH = -log [H+]

You just assume that of all the OH- ions in solution, they all come from the base and none come from water dissociating