# How are pKa tables used?

The realtion between ${K}_{A}$ and $p {K}_{a}$ is ${K}_{a} = {10}^{- p {K}_{a}}$. This value provides an essential constant for keeping track of concentration of $\left[{H}^{+}\right]$ in solutions.
Much like the way that pH is written using the logarithm function to convert the actual $\left[{H}^{+}\right]$ of a solution into a simpler value, so the ${K}_{a}$ of an acid can be converted into a $p {K}_{a}$ value.
Once you have the ${K}_{a}$ value, the applications that can be made from ${K}_{a}$ or $p {K}_{a}$ (whichever you prefer to use), include the ability to determine the $\left[{H}^{+}\right]$ in a solution of that acid, regardless of the concentration of the solution, or whether it is buffered for example.
${K}_{a}$ is an equilibrium constant, and as such is independent of the concentration of a solution. This makes it the best value for establishing the strength of that acid relative to others.