A buffer must able to maintain pH at or near a target pH. There are many applications in chemistry, but in practical aspects of our daily life. For example, a swimming pool is maintained at a pH XXX for XXX. For this and many other applications we will use buffers of appropriate strength. But, first let's establish what a buffer is. There are many mixtures of acids and bases that are not buffers. The video below discusses the general case of mixtures of acids and bases where there can be a reaction (acid + base -> salt + water). A buffer is a special case of an acid mixture with its conjugate base. Only when the acid and its conjugate base are present in the right ratio will a system be buffered. Thus, we start with the general observations of acid-base mixtures and hen proceed to the special case of the buffer.
Unlike the general case where acid and base react a buffer is a stable mixture of an acid and its conjugate base. Addition of strong acid or base to the mixture will change the ratio of .A=]/[HA], ubt will not have any other effect upon the solution. If the ratio is not affected too strongly the pH will remain relatively constant. THe easy way to predict the good condition for a buffer and to detrmine the buffer range is to use the Hendersen-Hasselbach equation. This is described in the next video.
