You can obtain the pH of a 0.100 M HCl solution by assuming that all of the

Question:

You can obtain the pH of a 0.100 M HCl solution by assuming that all of the H3O+ ion comes from the HCl, in which case the pH equals log 0.100 = 1.00. But if you want the pH of a solution that is 1.00 × 10-7 M HCl, you need to account for any H3O+ ion coming from water. (Why?) Note that the selfionization of water is the only equilibrium you need to account for. What is the pH of 1.00 × 10-7 M HCl?