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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: lifesayko on April 22, 2006, 12:11:05 PM

Title: Theoretical titration of an amino acid
Post by: lifesayko on April 22, 2006, 12:11:05 PM

Hi,
We recently did the titration of amino acids, and covered such things as the zwitter ion etc., and I understand these concepts, and I can identify them in a graph, but..
I was given theoretical solution of alanine, (100% protonated), and told to calculate the pH at various steps during titration. At the very beginning, I suppose I simply consider COOH as an acid, but as I approach the zwitter ion state, don't I need to consider both acids? How do I calculate that?

thanks in advance

Title: Re: Theoretical titration of an amino acid
Post by: Mitch on April 22, 2006, 08:12:39 PM

Can't you look up the pKa?

Title: Re: Theoretical titration of an amino acid
Post by: Equi on April 23, 2006, 03:54:07 AM

Quote from: Mitch on April 22, 2006, 08:12:39 PM

Can't you look up the pKa?

exactly, take a look at the Henderson-Hasselbalch equation (http://en.wikipedia.org/wiki/Henderson-Hasselbalch_equation).