Question

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

Answer 1

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 `pH`.

Without deriving the equation:

`pH = pK_a + log_10{[[A^-]]/[[HA]]}`

This tells us that when equal concentrations of ammonia and ammonium chloride are present, `pH = pK_a` because `log_10{1}=0`.

Because `Cl^-` is the conjugate base of a strong acid, it does not compete strongly for the proton, and has no effect on `pH`.