A buffer solution is an aqueous solution consisting of a weak acid and it's conjugate base or a weak base and its conjugate acid.It is a solution that tends to resist changes in PH when a small amount of acid or base is added to it.Many life forms thrive only in a relatively small pH range.An example of a buffer solution is blood.
Blood capacity is a quantitative measure of the resistance of a buffer solution to pH change of hydroxide ion.
Types of buffers.
Acidic buffer is prepared by mixing a strong acid and a weak acid, the strong acid serves as the salt.e.g ethanoic acid and sodium ethanoate.The solution is used to resist pH in an acidic medium.
CH3COO-Na(ag). ----------------> CH3COO- + Na+ (ag)
Ethanoic acid is slightly ionized.
CH3COOH(ag). +. H2O. ----------> CH3COO-. + H3O+
The presence of ethanoic acid in the system is to have enough amount of undissociated CH3COOH molecules to cope with the addition of the base.Hence,a buffer solution has enough conjugate acid-base pair.As sodium ethanoate is completely ionized and ethanoic acid is only slightly ionized,we assume that CH3COO- ions come from CH3COO-Na only as the contribution of CHCOO- ions from CH3COOH is negligible.
Reaction of a weak base and it's salt makes a basic buffer e.g aqueous ammonia and ammonium chloride.
It resist pH changes in a basic medium.Buffer solution are necessary to keep the correct pH for enzymes in many organisms to work
constant pH for the reaction to proceed. Buffers are extremely useful in these systems to maintain the pH at a constant value. This does not me that the pH of buffers does not change. It only means that the change in pH is not as much as it would be with a solution that is not a buffer
.Many enzymes work only under specific pH