A weak acid HX has the dissociation constant 1 ×10^-5 M. It forms a salt NaX on reaction with al

step 1 The hydrolysis reaction is given by x minus plus H2O will give HX plus OH minus. For a salt of w

A weak acid HX has the dissociation constant 1 ×10^-5 M. It...

A weak acid HX has the dissociation constant $1 \times 10^{-5} \mathrm{M}$. It forms a salt $\mathrm{NaX}$ on reaction with alkali. The percentage hydrolysis of $0.1 \mathrm{M}$ solution of $\mathrm{NaX}$ is
(a) $0.0001 \%$
(b) $0.01 \%$
(c) $0.1 \%$
(d) $0.15 \%$

Key Concepts

Dissociation Constant (Ka) and Its Role

The dissociation constant, Ka, represents the extent to which a weak acid dissociates into its constituents in solution. For a weak acid such as HX, a small Ka indicates limited ionization. In the context of the hydrolysis of its salt (NaX), the small value of Ka implies that the conjugate base X? is relatively stronger in its basic behavior (since Kb = Kw/Ka) and drives the hydrolysis equilibrium. Understanding Ka is thus crucial for predicting and calculating the degree of hydrolysis in salt solutions.

Percentage Hydrolysis

Percentage hydrolysis is a measure of the fraction of the salt that undergoes hydrolysis to form its weak acid (or weak base in the case of cations) in solution. It is computed by determining the concentration of the hydrolyzed species relative to the initial concentration of the salt, and then converting this fraction into a percentage. This concept is essential when assessing the extent to which a salt affects the pH of its aqueous solution.

Conjugate Base Hydrolysis Equilibrium

When a salt like one derived from a weak acid is dissolved in water, its anion acts as a conjugate base and hydrolyzes, reacting with water to form the weak acid and hydroxide ions. The equilibrium of this reaction is governed by the base hydrolysis constant, which is related to the acid dissociation constant (Ka) of the corresponding weak acid through the water dissociation constant (Kw). This relationship helps in quantifying the extent of hydrolysis.

Salt Hydrolysis

Salt hydrolysis refers to the reaction in which the anion or cation of a salt reacts with water to form the corresponding weak acid or weak base. For salts formed from a weak acid and a strong base, the anion (conjugate base) will react with water, typically producing OH? ions and creating a basic solution. This process is central to understanding how salts can affect the pH of a solution.

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