Pyridinium hydrochloride is a salt of a weak base (pyridine) and a strong acid (HCl). The pH of an aqueous solution of this salt is given by the relation:
pH = \(\frac{1}{2}\) [pKw - pKb - logC]
3.44 = \(\frac{1}{2}\) [14+logkb - log (0.02)]
6.88 = 14 + log Kb + 1.7
log Kb = -8.82
∴Kb = antilog(-8.82) = 1.514 x 10-9
