25. Ionisation constant of a weak base MOH, is given expression

Kb=[M+][OH-][MOH]

Values of ionisation constant of some weak bases at a particular temperature are given below

BaseKb Dimethylamine5.4×10-4 Urea1.3×10-14 Pyridine1.77×10-9 Ammonia1.77×10-5

Arrange the bases in decreasing order of the extent of their ionisation at equilibrium. Which of the above base is the strongest?


Given that, ionisation constant of a weak base MOH
Kb=[M+][OH-][MOH]
Larger the ionisation constant (Kb) of a base, greater is its ionisation and stronger the base.
Hence, dimethyl amine is the strongest base.
Kb Dimethylamine5.4×10-4>Ammonia1.77×10-5>Pyridine1.77×10-9>Urea1.3×10-14