Question
Ionisation constant of a weak base MOH, is given by the expression.$\text{K}_\text{b}=\frac{[\text{M}^+][\text{OH}^-]}{[\text{MOH}]}$
Values of ionisation constant of some weak bases at a particular temperature are given below:
Base
Dimethylamine
Urea
Pyridine
Ammonia
$K_b$
$5.4 \times 10^{–4}$
$1.3 \times 10^{–14}$
$1.77 \times 10^{–9}$
$1.77 \times 10^{–5}$
Arrange the bases in decreasing order of the extent of their ionisation at equilibrium. Which of the above base is the strongest?

Answer

Greater is the ionization constant ($K_b$) of a base, greater is the ionization of the base. Order of extent of ionization at equilibrium is dimethylamine > ammonia > pyridine > urea. Dimethylamine is the strongest base due to maximum value of $K_b​​​​​​​$.

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