Identify the conjugate acid and base of H₂PO₃^–.

Provide the K_a expressions for the ionization of citric acid (H₃C₆H₅O₇).

Which of the following is correct based on the relationship of the successive pK_a and K_b values for most polyprotic acids?

I. K_a1 < K_b1

II. K_a1 > K_a2 > K_a3

III. pK_a3 > pK_a2 > pK_a1

IV. K_b1 > K_b2 > K_b3

V. pK_b1 > pK_b2 > pK_b3