Kw at 25oC is 1.0?10-14.Likewise, the weaker an acid is, the smaller its Ka and the stronger its conjugate base (with a larger Kb).The stronger an acid is, the larger its Ka and the weaker its conjugate base (with a smaller Kb).-Anions of Weak Acids Anion of weak acids react with water to some extent to form OH-(and the conjugate acid).This relationship allows you to find Kb for the conjugate base of a weak acid or Ka for the conjugate acid of a weak base.