Short Answer
A basic salt is a salt that forms a basic solution (pH > 7) when dissolved in water. Basic salts are usually formed from a strong base and a weak acid.
For example, sodium acetate (CH₃COONa) is a basic salt because it is formed from sodium hydroxide (strong base) and acetic acid (weak acid). In water, the CH₃COO⁻ ion hydrolyzes to produce OH⁻ ions, making the solution basic.
Detailed Explanation :
Basic Salt
Basic salts are salts that give a pH greater than 7 in aqueous solutions. They are formed when a strong base reacts with a weak acid during neutralization. In such salts, the anion derived from the weak acid has a tendency to hydrolyze in water, producing hydroxide ions (OH⁻), which increases the pH of the solution. The cation from the strong base does not hydrolyze and remains neutral, so it does not affect the pH.
Basic salts are important in chemistry because they help explain the acid-base behavior of salts and are widely used in laboratories, industries, and chemical processes.
Formation of Basic Salts
Basic salts are formed through the reaction:
Strong base + Weak acid → Basic salt + Water
Examples:
- NaOH + CH₃COOH → CH₃COONa + H₂O
- KOH + HCN → KCN + H₂O
In these reactions:
- The strong base fully dissociates in water (e.g., Na⁺, K⁺).
- The weak acid partially dissociates (e.g., CH₃COOH, HCN).
- The anion of the weak acid hydrolyzes in water to produce OH⁻ ions.
How Basic Salts Work in Water
When a basic salt dissolves:
- It dissociates into cations and anions:
CH₃COONa → CH₃COO⁻ + Na⁺ - The anion of the weak acid hydrolyzes:
CH₃COO⁻ + H₂O → CH₃COOH + OH⁻ - The cation (Na⁺) remains neutral and does not react.
- The net result: OH⁻ ions increase → solution becomes basic.
This is the reason why salts formed from a strong base and weak acid give basic solutions.
Examples of Basic Salts
- Sodium acetate (CH₃COONa) – pH > 7 due to hydrolysis of CH₃COO⁻
- Sodium carbonate (Na₂CO₃) – CO₃²⁻ hydrolyzes → OH⁻ ions produced
- Potassium cyanide (KCN) – CN⁻ hydrolyzes → OH⁻ ions
- Sodium phosphate (Na₃PO₄) – PO₄³⁻ hydrolyzes → OH⁻ ions
These examples show that the anion from the weak acid is responsible for the basic nature of the solution.
Factors Affecting Basicity of Salts
- Strength of the Weak Acid
- Weaker acids produce anions that hydrolyze more readily → stronger basicity.
- Strength of the Strong Base
- Strong bases ensure cations do not hydrolyze, so the solution remains basic.
- Concentration of the Salt
- Higher concentration → more hydrolysis → higher pH.
- Temperature
- Hydrolysis reactions may slightly increase with temperature, slightly affecting pH.
Applications of Basic Salts
- Laboratory Chemistry
- Basic salts are used to study hydrolysis and buffer solutions.
- They help maintain slightly basic conditions in experiments.
- Industrial Applications
- Sodium carbonate and sodium acetate are used in detergents, food processing, and chemical production.
- Their basicity is important to control pH during processes.
- Biological Applications
- Certain basic salts are used in medicines and pH-regulating solutions.
- They help neutralize acidic conditions in biological systems.
- Environmental Applications
- Basic salts like carbonates can neutralize acidic soils or water, increasing alkalinity.
Summary of Basic Salts
- Formed from strong base + weak acid
- Anion hydrolyzes to produce OH⁻ ions
- Cation does not hydrolyze (neutral)
- Result: pH > 7 (basic solution)
- Examples: CH₃COONa, Na₂CO₃, KCN
This shows that hydrolysis of the anion is responsible for basic solutions.
Conclusion
A basic salt is a salt formed from a strong base and weak acid that produces a solution with pH greater than 7. The anion of the weak acid hydrolyzes in water to produce OH⁻ ions, while the cation remains neutral. Examples include sodium acetate, sodium carbonate, and potassium cyanide. Basic salts are widely used in laboratories, industries, biological applications, and environmental chemistry to maintain slightly alkaline conditions and control pH.