3. By definition the pH of a dilute solution of a weak acid equals its pKa only when the concentrations of unionized acid [HA] equals the concentration of its ionized conjugate base (A). At any given pH an acid will be mostly ionized or unionized depending on its pka. Given the following weak acids and their pka's decide whether the acid is mostly ionized or mostly unionized at the pH shown. [a] CHCOOH (pka = 4.76) at pH = 5.76 [b] HC(=O)OH [pKa = 3.75) at pH = 2.75 (c) CH,CHCHNH, fpka = 10.7) at pH = 8.7 (d) HS ipka 7.00 at pH=2 le] CH, OH Ipka = 15.5) at pH=9.5