Understanding Hydrolysis of Salts

Hydrolysis of salts is the reaction of salt ions with water to produce an acidic, basic, or neutral solution. It is an important concept in physical chemistry. In fact, the pH of a solution is also determined based on the nature of the salt and the ions it has in it.

Let us understand how hydrolysis happens in the case of salts. Read on to learn how salts undergo this process in detail.

What is Hydrolysis of Salts?

When the ions of a salt produce either H⁺ ions (for acidic solution), OH⁻ ions (for basic solution), or neither (for neutral solution) after reacting with water, then that reaction is referred to as the hydrolysis of that salt.

Breakdown of Hydrolysis of Salts

To know more about the hydrolysis of salts, it is important to know the electronic concept for the same.

Here is a brief drive into its concept.

When in water, the salt -

Salt → Cations + Anions

Whether hydrolysis occurs depends on whether the ions are derived from strong or weak acids and bases.

Types of Salts and Hydrolysis

The salts can be classified on the basis of the strength of acids/bases.

Strong Acid + Strong Base Salt:

No hydrolysis will occur
Neutral state of solution
pH ≈ 7
E.g., in salts like NaCl, KNO₃

Strong Acid + Weak Base Salt:

In this, the cation will hydrolyse with water
H⁺ ions produced → Acidic solution
pH < 7
E.g., in salts like NH₄Cl, AlCl₃

Weak Acid + Strong Base Salt:

In this, the anion will hydrolyse with water
OH⁻ ions produced → Basic solution
pH > 7
E.g., in salts like CH₃COONa, Na₂CO₃

Weak Acid + Weak Base Salt:

In this, both cation and anion will hydrolyse with water
pH will be based on the relative strength between acid and base
E.g., in salt like NH₄CH₃COO

Hydrolysis in NaCl

Forming of Hydrolysed Products in Hydrolysis of Salts

1. Product of Weak Base + Strong Acid → Acidic Salts

Since the cation (from a weak base) hydrolyses and releases H⁺ ions:

NH₄⁺ + H₂O ⇌ NH₃ + H₃O⁺

2. Product of Strong Acid + Strong Base → Neutral Salts

No hydrolysis occurs, solution remains neutral (pH ≈ 7):

Na⁺ + Cl⁻ → No hydrolysis

3. Product of Strong Base + Weak Acid → Basic Salts

Since the anion (from a weak acid) hydrolyses and releases OH⁻ ions:

CH₃COO⁻ + H₂O ⇌ CH₃COOH + OH⁻

Details At A Glance

Property	Details
Definition	Reaction of salt with water
Cause	Because of the presence of ions from weak acid or weak base
Types of Hydrolysis	Cationic, Anionic, Amphiprotic (both)
Neutral Salt Example	NaCl, KNO₃
Acidic Salt Example	NH₄Cl, AlCl₃
Basic Salt Example	CH₃COONa, Na₂CO₃
Weak Acid + Weak Base Salt	NH₄CH₃COO
Effect on pH	Solution can be acidic, basic, or neutral

Charge Density in Hydrolysis of Salts

The charge density on the ions decides the stability of the product, which is hydrolysed.

High charge density → Strong Hydrolysis

Summing Up

Thus, we can conclude by saying that the hydrolysis of salt is dependent on the strength of the parent acid and base. And in the salt solutions, they play a very important role in controlling the pH of that solution.