Nitric acid is a strong acid that is entirely ionized in aqueous solutions of concentrations ranging from 1% to 10% (1.5M). Nevertheless in more concentrated solutions part of nitric acid is present as un-ionized molecules of HNO3. For instance in a 50% solution (7.5M) at 25 C merely 33% the molecules of HNO3 dissociate into H+ and NO3-. Explain what is the value of Ka for HNO3?