Concentration H+ ions in Sulfuric Acid?

In sulfuric acid solutions, most of the hydrogen ions come from the first dissociation reaction, but the second dissociation step contributes to the concentration as well. Moreover, the more diluted a solution, the greater the percentage of acid that undergoes the second dissociation. For example, in a 0.20 solution, only about 5 of comes from the second dissociation step. With a 0.010 solution, the second dissociation reaction contributes almost a third of the final concentration