A few questions on pH < need help before a test

[peter444]

1. what is the pH of a solution that contains 1.56X 10^5 M hydrogen ions ?
2. Is there a pH above which the molarity of hydrogen of water is higher that the molarity of hydrogen ions derived from the dissolved chemical, and what is it?
3. What is the pH of 10^-8 M solution of HCl, when HCl fully dissociates in aqueous solution?

Thanks

[Sirus]

Don't really get the second question.

For 1 and 3, you should have gotten equations that relate hydrogen ion concentration and pH. Once you have that, 1 is easy, and for three, consider what [H^{+}] is when HCl fully dissociates.