Analytical Chemistry: Calculate the pH.

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SUMMARY

The discussion focuses on calculating the pH of a 5.0 x 10^-8 M solution of HCLO4, a strong acid. The initial approach of using the formula -log(5.0 x 10^-8) is incorrect, as it results in a pH greater than 7, indicating a basic solution, which contradicts the properties of strong acids. The key takeaway is that the contribution of H+ ions from the dissociation of water must be considered in this calculation to obtain an accurate pH value.

PREREQUISITES
  • Understanding of pH scale and its significance
  • Knowledge of strong acids and their dissociation
  • Familiarity with the concept of water dissociation and its contribution to H+ concentration
  • Basic logarithmic calculations
NEXT STEPS
  • Study the principles of strong acid dissociation in aqueous solutions
  • Learn how to calculate pH in the presence of weak acids and bases
  • Explore the concept of water's autoionization and its effect on pH
  • Review examples of pH calculations involving very dilute strong acids
USEFUL FOR

Chemistry students, analytical chemists, and educators seeking to deepen their understanding of pH calculations in the context of strong acids and their behavior in dilute solutions.

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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) .
 
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whatlifeforme said:
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.
 

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