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Topic: how to calculate % dissociation from PKa value and PH/conc.?  (Read 5848 times)

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Offline fiona_loveroy

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how to calculate % dissociation from PKa value and PH/conc.?
« on: October 20, 2008, 10:00:53 AM »
Hello, guys, anyone know how to find the extent of dissociation using PKa values and PH/conc.?

example: x (which is an organic acid) is only 1% dissociated in water....how do I find that 1% if I only know PKa and PH or
  • ?  ???


please help me! I'm down on my knees.. :'( :-[
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Offline Astrokel

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Re: how to calculate % dissociation from PKa value and PH/conc.?
« Reply #1 on: October 20, 2008, 10:16:07 AM »
huh? you want to find extent of dissociation but you were told it is 1%?
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Offline fiona_loveroy

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Re: how to calculate % dissociation from PKa value and PH/conc.?
« Reply #2 on: October 20, 2008, 10:27:43 AM »
no, that's just an example I gave....I don't know how that 1% has come from...that's why I need somebody to explain to me how to get that percentage if I know the PKa and conc. of that specific acid...
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Offline fiona_loveroy

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Re: how to calculate % dissociation from PKa value and PH/conc.?
« Reply #3 on: October 20, 2008, 10:30:29 AM »
I'm just giving a specific number to explain what I meant by 'extent of dissociation' just in case people don't understand my question.... :-[

just ignore the second paragraph if that helps... :-\
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Offline Astrokel

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Re: how to calculate % dissociation from PKa value and PH/conc.?
« Reply #4 on: October 20, 2008, 11:10:16 AM »
First find the amount of H+ dissociates using the acid dissociation formula(ICE table), and

extent of dissociation = (amt of H+ ionized / amount of initial acid ) x 100%
                              = [H+eqm] / [Acidinitial] x 100%
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Offline fiona_loveroy

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Re: how to calculate % dissociation from PKa value and PH/conc.?
« Reply #5 on: October 20, 2008, 11:23:24 AM »
thank you so much...! you saved my life^_^ ;D
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