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### Topic: Finding the Ka value of oxalic acid  (Read 16179 times)

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#### LilyFFC

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##### Re: Finding the Ka value of oxalic acid
« Reply #15 on: February 07, 2011, 03:13:42 PM »
Okay so the Ka2 = [H+][C2O42-] / [HC2O4-]

I know [H+] = 10-8.2

Would [HC2O4-] = [H2C2O4] ? And I'm not sure what [C2O42-] is equal to.

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##### Re: Finding the Ka value of oxalic acid
« Reply #16 on: February 07, 2011, 04:05:43 PM »
from the values of your experiment you can calculate how much OH- reacted with protons from the acid.

for each molecule of oxalic acid between 1 and 2 protons have reacted. The first proton will have reacted from each of the oxalic acid molecules, the second from only a portion; you can calculate exactly from how many using the amount of OH- that reacted

so: how many mole of OH- has reacted?
how many moles of oxalic acid has reacted?
so from how many moles of oxalic acid did the second proton react as well?

#### LilyFFC

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##### Re: Finding the Ka value of oxalic acid
« Reply #17 on: February 07, 2011, 04:23:35 PM »
I still don't follow - how am I supposed to calculate how much OH- reacted and how much I started with?

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##### Re: Finding the Ka value of oxalic acid
« Reply #18 on: February 07, 2011, 04:28:54 PM »
well, you know with how many moles of OH you started, right? (the number of moles of NaOH)

you know the pH at the end, and thus the concentration H+ at the end, right?

Do you remember the relation between [H+] and [OH-]? If you don't, then look it up and remember it!

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