Question

In the hydrolysis of salt of a weak acid and weak base……
A) the degree of hydrolysis of cation and anion is different
B) the degree of hydrolysis of cation and anion is same
C) the degree of hydrolysis of cation and anion is different and they can never be assumed same
D) the degree of hydrolysis of cation and anion is different, but they are close to each other when they are getting hydrolysed in the presence of each other.

Answer 1

The principle of interaction of ions of salt thereupon of water is called salt hydrolysis. Weak electrolyte (weak acid and weak base) is dissociated to a little extent in solution and there’s an equilibrium between the undissociated electrolyte and therefore ions formed in solution.

Complete step by step answer: Salts of a weak acid and base: Salts resulting from the neutralisation reaction between a weak and weak base are often mildly basic, mildly acidic, or neutral counting on the nature of the bases and acids involved. The degree of hydrolysis and ionization of water is independent of the concentration of the solution. An example of such salts is $C{H_3}COON{H_4}$.

The mechanism of formation of such ions are as follows:
$C{H_3}CO{O^ - } + N{H_4}^ + + {H_2}O \rightleftharpoons C{H_3}COOH + N{H_4}OH$
The $pH$of the aqueous solution of such salts are dented as
$pH = p{K_a} + p{K_b}$
That is, the $pH$ depends on the $p{K_a}$ and $p{K_b}$ of the acid and the base, respectively.

Due to the common ion effect, the hydrolysis of both the ions occurs to a greater extent within the presence of every other. The hydrolysis of the ion having a smaller value of ${K_n}$ is affected to a greater extent than the hydrolysis of the other ion. Hence, cation and anion have a special degree of hydrolysis, but when they are becoming hydrolysed within the presence of every other, their degrees of hydrolysis are on the brink of one another.

So the answer to this present question is option D i.e. the degree of hydrolysis is of cation and anion is different, but they are close to each other when they are getting hydrolysed in the presence of each other.

Note: Salt of a weak acid and weak base undergoes both cationic and anionic hydrolysis. In cationic hydrolysis it gives a weak base and in anionic hydrolysis it gives a weak acid. The ionization constant may be a measure of acid strength; the higher the ${K_a}$ value, the greater the number of hydrogen ions liberated per mole of acid in solution and therefore the stronger is that the acid.