Short Answer

Some salts form basic solutions because they are made from a strong base and a weak acid. In water, the anion of the weak acid reacts with water to produce OH⁻ ions, which increases the basicity of the solution.

For example, sodium acetate (CH₃COONa) forms a basic solution because CH₃COO⁻ (from weak acid CH₃COOH) reacts with water to produce OH⁻ ions. The stronger the base and weaker the acid, the more basic the solution becomes.

Detailed Explanation :

Basic Salts

Salts are formed from the neutralization of acids and bases. While many salts produce neutral solutions, some produce basic solutions due to the hydrolysis of ions in water. A basic salt solution has a pH greater than 7.

Basic solutions form when a salt is derived from a strong base (like NaOH or KOH) and a weak acid (like CH₃COOH or HF). The anion of the weak acid reacts with water, generating hydroxide ions (OH⁻), which makes the solution basic.

How Basic Solutions Form

When salts dissolve in water, they dissociate into ions:

Salt → Cation⁺ + Anion⁻

• The anion from the weak acid reacts with water:

A⁻ + H₂O → HA + OH⁻

• This reaction produces OH⁻ ions, increasing the basicity.
• The cation from the strong base (like Na⁺ or K⁺) does not hydrolyze because it is neutral and does not affect pH.

The overall result is a solution with excess OH⁻, which makes it basic.

Examples of Basic Salts

1. Sodium Acetate (CH₃COONa)

• Weak acid: CH₃COOH
• Strong base: NaOH
• Hydrolysis of CH₃COO⁻ produces OH⁻ → basic solution

1. Sodium Carbonate (Na₂CO₃)

• Weak acid: H₂CO₃
• Strong base: NaOH
• CO₃²⁻ reacts with water → OH⁻
• Solution pH > 7

1. Sodium Citrate (Na₃C₆H₅O₇)

• Weak acid: Citric acid
• Strong base: NaOH
• Produces slightly basic solution

Factors Affecting Basicity of Salt Solutions

1. Strength of Parent Acid

• Weaker acids produce anions that hydrolyze more readily → stronger basic solution.
• Strong acids (like HCl) produce anions that do not hydrolyze → neutral solution.

2. Strength of Parent Base

• Strong bases like NaOH or KOH ensure that cations do not hydrolyze and do not counteract the basicity.

3. Concentration of Salt

• Higher concentration → more anions available → more OH⁻ produced → higher pH.

4. Temperature

• Hydrolysis reactions can be slightly temperature-dependent, affecting OH⁻ production.

Explanation Using Hydrolysis

Basic salt formation is a type of salt hydrolysis:

• The anion of the weak acid reacts with water to form OH⁻:
  A⁻ + H₂O → HA + OH⁻
• The cation from the strong base does not react.

This selective hydrolysis explains why salts from strong base + weak acid always give basic solutions.

Applications and Importance

1. Laboratory Chemistry

• Basic salts are used to study hydrolysis, buffer solutions, and pH control in chemical experiments.

2. Industrial Processes

• Sodium carbonate and sodium acetate are used in:
  • Detergent production
  • Food preservation
  • Textile processing
• Their basicity is important for process control.

3. Environmental Chemistry

• Basic salts in water affect soil and water pH.
• For example, carbonate salts can increase the alkalinity of soil and natural waters.

4. Biological Systems

• Basic salts help maintain pH in certain biological fluids and are used in medications like antacids.

Summary of Why Some Salts Are Basic

• Salt is formed from a strong base and weak acid.
• The anion of the weak acid hydrolyzes in water.
• Hydrolysis produces OH⁻ ions, increasing pH.
• Cations from strong bases do not hydrolyze.
• Resulting solution is basic (pH > 7).

Conclusion

Some salts form basic solutions because they are composed of a cation from a strong base and an anion from a weak acid. The anion reacts with water to produce OH⁻ ions, which increases pH. Examples include sodium acetate, sodium carbonate, and sodium citrate. The extent of basicity depends on the strength of the parent acid, salt concentration, and temperature. Basic salts are important in laboratories, industries, environmental chemistry, and medicine, where controlling pH is essential.