What is the ph of the resulting solution - histidine has

Question

1. The pk_a values of a compound with two ionizable groups are pk₁=4.10 and pk₂ between 7 and 10. We have 10 mL of a 1.0 M solution of this compound at a pH of 8.0. She adds 10.0 mL of 1.0 M HCL, which changes the pH to 3.20. What is pk₂?

2. Histidine has ionizable groups with pKa values of 1.8, 6.0, and 9.2. A biochemist makes up 100 mL of a 0.100 M solution of histidine at a pH of 5.40. She then adds 40 mL of 0.10 M HCl. What is the pH of the resulting solution?