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Topic: PKa(H3O+/H2O) and PKa(H2O/HO-)  (Read 16614 times)

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Offline Shah

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Re: PKa(H3O+/H2O) and PKa(H2O/HO-)
« Reply #15 on: February 14, 2011, 09:08:53 AM »
http://www.chembuddy.com/?left=pH-calculation&right=pH-buffers-henderson-hasselbalch

in this site it is written that if we mix  0.1 M of dichloroacetic acid of pKa=1.5 and 0.05 M NaOH. The pH won't be 1.5 . Proper pH value can be calculated using pH calculator - and it is 1.78. The reason is simple. Dichloroacetic acid is strong enough to dissociate on its own and equilibrium concentration of conjugate base is not 0.05 M (as we expected from the neutralization reaction stoichiometry) but 0.0334 M.

The question is: through my own calculations, the equilibrium concentration of conjugate base was approximately 0.0666 and not 0.0334, while the equilibrium concentration of the acid was 0.0334. Am i right or what is written in the site is right?


Offline Shah

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Re: PKa(H3O+/H2O) and PKa(H2O/HO-)
« Reply #16 on: February 15, 2011, 08:41:42 AM »
What i meant to ask is: if we prepared a solution of 1 liter that contains  0.1 M of dichloroacetic acid of pKa=1.5 and 0.05 M NaOH. Can anybody calculate the concentration of conjugate base?

plzzzzzzzzzz help and thanks

Offline Shah

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Re: PKa(H3O+/H2O) and PKa(H2O/HO-)
« Reply #17 on: February 15, 2011, 02:35:15 PM »
would the number of moles of the conjugate base be 0.0334 M or 0.0666? i would be thankful if you could show me the calculations?

Offline Shah

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Re: PKa(H3O+/H2O) and PKa(H2O/HO-)
« Reply #18 on: February 18, 2011, 07:49:46 AM »
can't anybody help ????

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