# Why should you use a buffer in chemistry?

To moderate gross changes in $p H$.
The buffer equation is $p H = p {K}_{a} + {\log}_{10} \left(\frac{\left[{A}^{-}\right]}{\left[H A\right]}\right)$.
And thus use of a buffer allows fairly stable values of $p H$, even with the addition of random quantities of acid or base. Biological systems are extensively buffered, in that gross changes in $p H$ would probably be deleterious to an organism.