Question

what is buffer solution?

Answer 1

A buffer solution (more precisely, pH buffer or hydrogen ion buffer) is an aqueous solutionconsisting of a mixture of a weak acid and its conjugate base, or vice versa. Its pH changes very little when a small amount of strong acidor base is added to it.

Answer 2

A buffer solution is a solution that is able to maintain its pH, even when a little acid or base is added.  The solution is usually made up of a weak base and its conjugate acid (or a weak acid and its conjugate base), which exist in an equilibrium.  When another base or acid is added to the solution, this shifts the equilibrium (the result of an increase or decrease in hydrogen ion dissociation), which tends to compensates for the introduction of additional base or acid.

These solutions are very useful for reactions that require well-controlled pH, in an environment or product where pH is normally difficult to control (due to the production of reaction byproducts that may change the pH when no buffer is used, for example).  Enzymes and other reactions common to biochemistry are examples where buffers are used.

Blood for example, is a buffer solution: the carbonic acid and its conjugate base, bicarbonate, in the blood plasma helps keep the pH of the blood constant.

Citric Acid (and its conjugate base, sodium citrate) for example is used throughout the food and cosmetics industries to regulate pH
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