# What solution is formed when a weak acid is mixed with quantities of its conjugate base?

Mar 21, 2016

Formation of a buffer solution is described.

#### Explanation:

A buffer solution is a mixture of a weak acid and its conjugate base in appreciable concentrations, which acts to resist gross changes in $p H$.

Without deriving the equation:

$p H = p {K}_{a} + {\log}_{10} \left\{\frac{\left[{A}^{-}\right]}{\left[H A\right]}\right\}$

This tells us that when equal concentrations of ammonia and ammonium chloride are present, $p H = p {K}_{a}$ because ${\log}_{10} \left\{1\right\} = 0$.

Because $C {l}^{-}$ is the conjugate base of a strong acid, it does not compete strongly for the proton, and has no effect on $p H$.