What is the primary characteristic of a diprotic acid titration?

If 100 mL of 0.100 M diprotic acid is titrated with 0.050 M NaOH, what is the volume of NaOH required to reach the first equivalence point?

Calculate the pH of a buffer solution formed by 0.00375 moles of conjugate base and 0.00625 moles of weak acid using the Henderson-Hasselbalch equation. Assume pK_a = 1.8.

After the first equivalence point, 50 mL of 0.050 M KOH is added to 100 mL of 0.100 M diprotic acid. Calculate the pH considering the removal of the second acidic hydrogen. Assume K_a2 = 6.4 x 10^-8.

After the second equivalence point, 20 mL of 0.050 M KOH is added to 100 mL of 0.100 M diprotic acid. Calculate the resulting pH.