A buffer solution is a special type of solution that resists changes in pH when small amounts of an acid or a base are added.
Key Features:
- It contains a weak acid and its salt with a strong base (acidic buffer) or a weak base and its salt with a strong acid (basic buffer).
- The weak acid/base and its salt work together to neutralize added H⁺ or OH⁻ ions, keeping the pH nearly constant.
- Buffers are important in biological systems, industry, and laboratories where maintaining a stable pH is necessary.
Examples:
- Acidic buffer: A mixture of acetic acid (CH₃COOH) and sodium acetate (CH₃COONa). Maintains pH around 4–6.
- Basic buffer: A mixture of ammonia (NH₃) and ammonium chloride (NH₄Cl). Maintains pH around 9–11.
- Biological buffer: Blood contains a carbonic acid–bicarbonate buffer system that keeps pH near 7.4.
In short: A buffer solution is a mixture that prevents large pH changes, making it essential for chemical and biological stability.