Analytical Chemistry: Calculate the pH.

[whatlifeforme]

Homework Statement

Calculate the pH of 5.0 x 10^-8 M HCLO4. What fraction of the total H+ in this solution is derived from dissociation of water?

Homework Equations

The Attempt at a Solution

The only thing I know to do is take -log(5.0 x 10^-8) .

 

[Borek]

The only thing I know to do is take -log(5.0 x 10^-8) .

That's not correct in this case, as it yields pH above 7, which suggests - quite nonsensically - that acid solution is slightly basic. Besides, question contains a strong hint telling you why this approach yields incorrect result.

Compare discussion here: pH of a strong acid.