The pKa of a weak acid (HA) is 4.5. The pOH of an aqueous buffered solution of HA in which 50% of the acid is ionized is

For buffer solution :pH = pKa + log  SaltAcid = 4.5 + log  SaltAcid As HA is 50% ionized so  Salt = Acid pH = 4.5 pH + pOH = 14 ∴     pOH = 14 - 4.5 = 9.5