Calculate pH of 1.00x10-8 M HClO4 Solution

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The pH of a 1.00x10-8 M HClO4 solution is calculated to be 6.98, not 8, due to the effects of water's autoionization. At such a low concentration, the contribution of H3O+ ions from the acid is not the only factor; the autoionization of water adds additional H3O+ ions, affecting the overall pH. This phenomenon occurs because the concentration of the acid is less than 1e-7 M, which is significant in dilute solutions. Understanding this interaction is crucial for accurately determining pH in very dilute strong acid solutions. The solution highlights the importance of considering both the acid's concentration and the autoionization of water in pH calculations.
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Homework Statement



The pH of a 1.00x10-8 M solution of HClO4 is

Homework Equations



-log(H3O+)

The Attempt at a Solution



I thought I could just do -log(1.00x10^8) = 8, but the answer is actually 6.98. Why?

Does it have anything to do with it being a strong acid?
 
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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.
 
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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.

thanks a lot.
 
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