The pH of a 1.00x10-8 M solution of HClO4 is calculated to be 6.98, not 8, due to the effects of water's autoionization. In dilute solutions where the concentration of the acid is less than 1.0x10-7 M, the contribution of hydronium ions from water must be considered. This phenomenon is critical when dealing with strong acids in low concentrations, as demonstrated in the referenced example from the University of Waterloo.
PREREQUISITESChemistry students, educators, and anyone interested in understanding acid-base equilibria and pH calculations in dilute solutions.
sumzup said:Since the concentration is extremely dilute and is < 1e-7, a phenomenon known as autoionization of water takes place...check out Example 3 under Strong Acids on http://www.science.uwaterloo.ca/~cchieh/cact/c123/stacids.html" for how to solve.