If an amino group has a Ka of 10^-9 what is its Pka.

Ok easy enough its going to be 9.

Part 2

What is the ratio of protenated to unprotenated moieties at equilbrium?

Answer 10^9

I thought the formula for Ka is

Ka = [A-][H+]/[HA]

How come they are not accounting for the concentration of [H+] ions in the solution and are simply saying the ratio of protenated to unprotenated is 10^9?