Chemistry

Analytical Chemistry question: Find the pH and the concentration of each species of lysine in a solution of 0.0010 M lysine*HCL.

I know that the pKAs of lysine are
(1.77)(CO2H)
9.07 (�-NH3)
10.82 (�-NH3)
but I am not sure where to go from there.

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  1. Note: I am unfamiliar with how the alha amino acids dissociate so look at what follows with a skeptical eye. Here is what I think.
    With a concn of 0.001 the hydrochloride will consist of the fully protonated amino acid plus the chloride ion. You can assign 0.001 to (Cl^-) right off the bat.
    Then you note that the pKa2 and pKa3 is so much higher than pKa1 so the ionization of the first group (the COOH) can be calculated and ignore that from pKa2 and pKa3. Thus, treat the first ionization just like you would a simple monoprotic acid, HA
    ........HA ==> H^+ + A^-
    I....0.001.....0......0
    C......-x......x......x
    E....0.001-x...x.......x

    Solve for x and convert to pH. Undoubtedly you will need to use the quadratic equation. Here is a web site that may prove useful to you. The information on this site does not ignore the other species as I have done.
    http://www.cmu.edu/bio/education/courses/03310/HomeworkProblems/ProblemC1.pdf

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    posted by DrBob222

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