Question

Ionization constant of a weak base$MOH$, is given by the expression
${K_b} = \dfrac{{\left[ {{M^ + }} \right]\left[ {O{H^ - }} \right]}}{{\left[ {MOH} \right]}}$
Values of ionization constant of some weak base at particular temperature are given below:

Base dimethyl amine	Urea	Pyridine	Ammonia
${K_b} = 5.4 \times {10^{ - 4}}$	${K_b} = 1.3 \times {10^{ - 14}}$	${K_b} = 1.77 \times {10^{ - 9}}$	${K_b} = 1.77 \times {10^{ - 5}}$

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

Answer 1

We know that dissociation constant is an equilibrium constant which measures the tendency of a bigger object to separate reversibly into smaller components the equilibrium constant also can be called ionization constant.
For a general reaction:
${A_x}{B_y} \rightleftharpoons xA + yB$
The dissociation constant of the reaction is,
${K_d} = \dfrac{{{{\left[ A \right]}^x}{{\left[ B \right]}^y}}}{{\left[ {{A_x}{B_y}} \right]}}$
The equilibrium concentrations of A, B are$\left[ A \right]$,$\left[ B \right]$, and$\left[ {{A_x}{B_y}} \right]$.

Complete step by step answer:
A weak base may be a base that ionizes only slightly in a solution. Recall that a base is often defined as a substance, which accepts a proton from another substance. When a weak base like ammonia is dissolved in water, it accepts a Hydrogen ion from water, forming the hydroxyl ion and therefore the conjugate acid of the bottom, the ammonium .The numerical value of Kb may be a reflection of the strength of the bottom. Weak bases with relatively higher ${K_b}$ values are stronger than bases with relatively lower ${K_b}$values.
The Values of ionization constant of the weak base at given temperature are given below:

Base dimethyl amine	Urea	Pyridine	Ammonia
${K_b} = 5.4 \times {10^{ - 4}}$	${K_b} = 1.3 \times {10^{ - 14}}$	${K_b} = 1.77 \times {10^{ - 9}}$	${K_b} = 1.77 \times {10^{ - 5}}$

We know that the greater the value of ${K_b}$ stronger will be the base. Between the given bases, the strongest base is Dimethylamine.

Therefore, the order will beBase dimethyl amine>Ammonia>Pyridine>urea . .

Note: As we know that acids, bases can either be strong or weak, counting on their extent of ionization. A robust base may be a base, which ionizes completely in a solution . The foremost common strong bases are soluble metal hydroxide compounds like potash. Some metal hydroxides aren't as strong just because they're not as soluble. Lime is merely slightly soluble in water, but the portion that does dissolve also dissociates into ions.