posted by Chris .
Consider a 9.5e-10 M solution of HClO4 at 283 K. What is the pH of the solution?
First you must recognize that this is a very weak acid solution and that the H^+ contributed by the HClO4 is much less than the H^+ contributed by the H2O.
(H^+)(OH^-) = Kw
(H^+) = x from the H2O and 9.5E-10 from the HClO4.
(OH^-) = x
Kw you must look up (in your text) for Kw at 10 celsius. (283K-273 = 10 C).
Solve for x (H^+) and convert to pH.