ses Learning Goal: Determine the pH of a solution of an amino acid with two func

Question

ses Learning Goal: Determine the pH of a solution of an amino acid with two functional groups relevant to acid-base chemistry Hom The amino acid glycine, the simplest of the 20 natural amino acids, combines a carboxylic acid and an amine in a single molecule. The pKat for the carboxylic Ka2 acid is 2.34, the pks2 for the amino group is 9.60. This resuits in 4 distinct protonation states for this small moleule, which are depicted above. For e Matesimplicity, we can assume that both functional groups can be treated independently. L.e. that their pka does not depend on the protonation state of the other functional group Ka,1 1 11 Ka1 Set up the required system of equations to calculate the pH of this solution for a given total concentration of glycine. You may find the website below useful, but you can use approximations that simplity this problem somewhat without NH2CH2C0o- affecting the accuracy http:l/keisan.casio.com/exed/system/1181809416 Ka,2 Test your results by double-checking that all your equations are fufilled by your solution and do not result in unphysical properties Sci bisor

Explanation / Answer

Part A)

Glycine + H2O <==> glycinate + H3O+

let x amount dissociated

Ka1 = [glycinate][H3O+]/[glycine]

4.6 x 10^-3 = x^2/0.1

x = [H3O+] = 0.0214 M

pH = -log[H3O+] = 1.669

Part B)

Glycine + H2O <==> glycinate + H3O+

let x amount dissociated

Ka1 = [glycinate][H3O+]/[glycine]

4.6 x 10^-3 = x^2/0.01

x = [H3O+] = 0.0068 M

pH = -log[H3O+] = 2.169

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