Question: how to get keq from pka?
Answer: Finding Keq From pKa If you already have the pKa value of a compound, you can work out its Ka. For example, the pKa value of lactic acid is 3.86. The first thing you do is multiply the pKa value by negative one to invert its sign. In the case of lactic acid, this is 3.86 x (-1) = -3.86.