What is a key difference between diprotic and monoprotic buffers?

Calculate the pH of a buffer solution containing 0.1 M HSO₃^- and 0.05 M SO₃^2- with pK_a2 = 7.2.

How do you convert 0.5 moles of a substance into molarity if the solution volume is 2 liters?

Calculate the moles of H₂A in a 0.5 L solution with a concentration of 0.2 M.

In a diprotic buffer system with H₂A, HA^-, and A^2-, which form should be used with pK_a2 in the Henderson-Hasselbalch equation?