The amino acid histidine (H 3 C6 H 8 N 3 O 2 ) is a polyprotic acid with three protons and is titrated
with NaOH. Given that the pKaās of the protons in aqueous solution at 25 °C are as follows:
pK a1 = 1.82
pK a2 = 6.04
pK a3 = 9.17
how many equivalents of NaOH will need to be added in the titration to find when the pH = pK a2 ?