Titration question

[virtualmaster999]

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Hi everyone!

I'm getting a little tripped up on a titration concept with a titration graph, which seems straightforward, but still confuses me.

I've gone over some questions where you are being asked, "which is mostly likely the acid being titrated?" and you have four answers, either with all pKa or pKb. Now I first thought that you are supposed to look at what kind of titration i.e strong acid, weak base etc. But it looks like the way to get the answer is by looking at the half eq pt to find the pH, which will equal the pKa. That pH gives me the answer (or i have to just solve for pKb). So is the way to solve these kinds of problems by looking at the 1/2 eq pt, and comparing the answers?

Thanks as always!

 

[DAT Destroyer]

Hi everyone!

I'm getting a little tripped up on a titration concept with a titration graph, which seems straightforward, but still confuses me.

I've gone over some questions where you are being asked, "which is mostly likely the acid being titrated?" and you have four answers, either with all pKa or pKb. Now I first thought that you are supposed to look at what kind of titration i.e strong acid, weak base etc. But it looks like the way to get the answer is by looking at the half eq pt to find the pH, which will equal the pKa. That pH gives me the answer (or i have to just solve for pKb). So is the way to solve these kinds of problems by looking at the 1/2 eq pt, and comparing the answers?

Thanks as always!

Yes.....for example.....if we are titrating a weak acid with a strong base,,,,,and given the curve ......we locate the ml to reach the Equivalence point..... say it is 50 ml.......we then realize that 25 ml is the HALF EQUIVALENCE point......then....extrapolate from the graph.....and note the pH. This means that pH = pKa since we are at the Half Equivalence point. If the pH was 9,,,,,,the pKa is also 9...thus the Ka is 1 x 10 exp -9. This is a favorite Freshmen Chem problem at NYU !!!!

If you have a specific question.....I can show an even faster way......

Dr. Romano

 

[virtualmaster999]

Yes.....for example.....if we are titrating a weak acid with a strong base,,,,,and given the curve ......we locate the ml to reach the Equivalence point..... say it is 50 ml.......we then realize that 25 ml is the HALF EQUIVALENCE point......then....extrapolate from the graph.....and note the pH. This means that pH = pKa since we are at the Half Equivalence point. If the pH was 9,,,,,,the pKa is also 9...thus the Ka is 1 x 10 exp -9. This is a favorite Freshmen Chem problem at NYU !!!!

If you have a specific question.....I can show an even faster way......

Dr. Romano

Thank you!!