The diprotic acid H2A has pK1 = 4.00 and pK2 = 8.00.
(a) At what pH is [H2A] = [HA-]?
(b) At what pH is [HA-] = [A2-]?
(c) Which is the principal species at pH 2.00: H2A, HA-, or A2-?
(d) Which is the principal species at pH 6.00?
(e) Which is the principal species at pH 10.00?