pH of a buffer solution varies with the type of buffer.
A buffer solution resists pH changes even when a strong acid or base is introduced, or when the solution is mixed with water. In the presence of added acid or base, the buffer solution demonstrates the ability to limit the extent of pH changes.
The typical composition of a buffer solution includes a weak acid or base of a particular concentration and its conjugate base or acid of a particular concentration. Buffers are used to keep pH levels constant or close to constant. Live organisms and many laboratory procedures need to buffer systems.