Question

How do you determine the pKa of an acid?

Answer 1

We would use the relationship, `pH=pK_a+log_10{[[A^-]]/[[HA]}}`

Explanation:

So the acid `HA` would be titrated with small aliquots of base while the `pH` of the solution was monitored with a `pH` meter. At the point of half equivalence (which would only be apparent after the endpoint!), `[A^-]=[HA]`, and `pH=pK_a` (because `log_(10)1=0`.