A 50mL solution of Histidine-HCl (Histidine: pKa1=1.8, pKa2=9.2, pKa3=6.0)is titrated with 0.500M NaOH. What is the expected pH of the histidine solution at the points in the titration when 14.0mL, 26mL, and 38mL of the NaOH titrant is added?

Answer 1

Here is a good tutorial on histidine HCl.
http://www.chem.uiuc.edu/CLCtutorials/104/AminoAcidTitrations/SeeIt.html