pH and Buffer

pH is a measure of the concentration of H⁺ [H₃O⁺] ions in a solution. Only the concentration of H⁺ and OH^- molecules determine the pH. When the concentration of H⁺ and OH^- ions are equal, the solution is said to be neutral. If there are more H⁺ than OH^- molecules the solution is acidic, and if there are more OH^- than H⁺ molecules, the solution is basic.

Buffer

A buffer solution is one which resists changes in pH when small quantities of an acid or an alkali are added to it. An acidic buffer solution is simply one which has a pH less than 7. Acidic buffer solutions are commonly made from a weak acid and one of its salts - often a sodium salt.

To be able to add a strong acid or base to a solution without causing a large change in the pH, we need to create a buffer solution. A buffer solution contains both a weak acid (HA) and its conjugate base (A^-).

A buffer solution (more precisely, pH buffer or hydrogen ion buffer) is an aqueous solution consisting 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 acid or base is added to it. Buffer solutions are used as a means of keeping pH at a nearly constant value in a wide variety of chemical applications. In nature there are many systems that use buffering for pH regulation. For example, the bicarbonate buffering system is used to regulate the pH of blood.