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Working out pKa from titration curve graph

I hve a book(http://www.amazon.co.uk/Calculations-AS-A-Level-Chemistry/dp/0582411270) that says that you can work out the pH and pKa from a titration curve.
It says all this stuff about how pKa and pH are equal and you need to half the volume...I have no idea what it means!
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Reply 1
Avatar for lamalas600
lamalas600
1
Before you get the neutralisation point, adding aicd/alkali doesn't do much, as it is a buffer solution.
This also means that [HA]=[A-]
leaving Ka=[H+] in the acid equation
getting -logKa=-log[H+]
which is pka=pH
Original post by lamalas600
Before you get the neutralisation point, adding aicd/alkali doesn't do much, as it is a buffer solution.
This also means that [HA]=[A-]
leaving Ka=[H+] in the acid equation
getting -logKa=-log[H+]
which is pka=pH


:eek: huh?
Reply 3
Avatar for lamalas600
lamalas600
1
Maybe I'm awful at explaining... lol what don't you understand from that? :smile:
Confusion number 1 how'd you know it's a buffer solution?
Reply 5
Avatar for lamalas600
lamalas600
1
When you do a titration, there are no changes at all until a sudden colour change, this means that the pH isn't changing that much when your adding alkali/acid, until the neutralisation point.
Buffer - Resists changes in pH when small amounts of acid/alkali are added to it.
Original post by lamalas600
When you do a titration, there are no changes at all until a sudden colour change, this means that the pH isn't changing that much when your adding alkali/acid, until the neutralisation point.
Buffer - Resists changes in pH when small amounts of acid/alkali are added to it.


So it acts as a buffer until the equivalence point (or is it the end point)?
Reply 7
Avatar for lamalas600
lamalas600
1
Original post by The Illuminati
So it acts as a buffer until the equivalence point (or is it the end point)?


Yes, and equivalence point and end point are the same thing

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