Question

a) Hydrolysis of salts.​

Answer 1

Answer:

A salt is an ionic compound that is formed when an acid and a base neutralize each other. Salt hydrolysis is a reaction in which one of the ions from a salt reacts with water, forming either an acidic or basic solution

Answer 2

Explanation:

Salt is a compound formed by the neutralization reaction between an acid and a base. They generally ionize in water furnishing cations and anions. The cations or anions formed during ionization of salts either exist as hydrated ions in aqueous solutions or interact with water to regenerate the acids and bases. The process of interaction between cations or anions of salts and water is known as hydrolysis of salts. On the basis of hydrolysis, salts are divided into three categories:

Acidic salts

Basic salts

Neutral salts

Let us discuss hydrolysis of salts of the following types:

Salts of strong acid and strong base: Salts formed by the neutralization of strong acid and strong base are neutral in nature as the bonds in the salt solution will not break apart. They generally get hydrated but do not hydrolyse. Therefore, such salts are generally known as neutral salts.

For example: NaCl

Salts of weak acid and strong base: Salts formed by the neutralization of weak acid and strong base are basic in nature. For example: CH3COONa

CH3COONa (aq) → CH3COO− (aq) + Na+ (aq)

Acetate ion formed undergoes hydrolysis to form acetic acid and OH– ions.CH3COO−(aq) + H2O ⇋ Ch3COOH(aq) + OH−(aq)

As we know acetic acid is a weak acid, it remains unionized in the solution. This results in an increase in concentration of OH– ions which makes the solution alkaline.pH of the solution is greater than7.

Salts of strong acid and weak base: Salts formed by the neutralization of strong acid and weak base are acidic in nature. For example: NH4Cl

NH4Cl(aq) → Cl−(aq) + NH+4(aq)

Ammonium ion formed undergoes hydrolysis to form ammonium hydroxide and H+ ions.

NH+4(aq) + H2O ⇋ NH4OH(aq) + H+(aq)

As we know ammonium hydroxide is a weak base, it remains unionized in the solution. This results in an increase in concentration of H+ ions which makes the solution acidic. pH of such solutions is less than 7.

Salts of weak acid and weak base: Salts formed by the neutralization of weak acid and weak base are acidic, basic or neutral depending on the nature of acids and bases involved. For example: CH3COONH4.General mechanism for the hydrolysis of ions formed from these salts:

CH3COO− + NH+4 + H2O ⇋ CH3COOH + NH4OH

Degree of hydrolysis in such cases is independent of the concentration of solution and pH of such solutions is given by:

pH= 7 + 12 (pKa – pKb)

Hence, we can say that the pH of a solution can be less than 7 or greater than 7 depending on the values of pKa and pKb.