Question

Glutamic acid is triprotic amino acid with pKa values of 2.23, 4.42, and 9.95. You
are given a 0.100 M solution of it in its fully protonated form (H3A). How many moles of KOH must be added to 100 mL of this solution to make a solution with a pH of 5.00.

I used 2.23 as the pka to obtain the concentrations H+ and H2A-. From there I keep getting the wrong answer when I add OH-

Answer 1

I would think you would use the 4.42 value for pH = 5.0 buffer.