Buffer Solution: What is Buffer Capacity and Solution

What is a buffer solution?

A buffer solution or hydrogen ion buffer is defined as an aqueous solution comprising a mixture of a weak acid and its conjugate base or vice versa.

There is a change in pH when a small amount of a strong base or acid is added.

What is buffer capacity?

The ability of buffer to resist pH change of solution on adding hydroxide ions. It is also called buffer index, efficiency, coefficient, or value.

The symbol β denotes it. The buffer capacity decreases as the purity of fresh water increases.

Types of buffer solution

There are two types of pH buffers. They are:

1. Solutions of single substances: A salt solution of a weak base and weak acid. Example CH3COONH4 (ammonium acetate)
2. Solutions of Mixtures: These are further divided into two,
   1. Acidic buffer: These have a pH below seven and comprise a weak acid and one of its salts. For example, a sodium acetate and acetic acid mixture acts as a pH buffer with a pH value of about 4.75.
   2. Primary buffer or alkaline buffer: These have a pH value above seven and comprise a weak base and one of its salts. For example, an ammonium hydroxide and chloride mixture acts as a buffer solution with a pH of about 9.25.

Buffer solution preparation

By knowing the pKa of the acid and pKb of the base, you can make a buffer of known pH by controlling the ratio of salt and base or salt and acid.

Buffers are prepared by mixing a weak base with its conjugate acid or a weak acid with its conjugate base.

For example, a widely used buffer in laboratories, phosphate buffer, consists of a weak base and its conjugate acid. Its pH value is 7.4.

Uses of buffer solution

• Buffers are widely used in industrial processes such as fermentation and controlling dye.
• It is used in the manufacturing of pharmaceuticals.
• The human body uses buffers to maintain a blood pH of 7.35 to 7.45.
• Enzymes require precise pH levels to react appropriately.

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