Which acid is the best choice to create a buffer with ph = 7.66?

Question

Itzel

Chemistry

16 March, 13:14

Which acid is the best choice to create a buffer with ph = 7.66?

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Answers (1)

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Ruffe · Answer 1

The best choice is h ypochlorous acid (HClO) because it has the nearest value of pK to the desired pH.

pKa of hypochlorous acid is 7.54

If we know pKa and pH values, we can calculate the required ratio of conjugate base (ClO⁻) to acid (HClO) from the following equation:

pH=pKa + log (conc. of base) / (conc. of acid)

7.66=7.54 + log (conc. of base) / (conc. of acid)

7.66 - 7.54 = log (conc. of base) / (conc. of acid)

0.12 = log (conc. of base) / (conc. of acid)

(conc. of base) / (conc. of acid) = 10⁻⁰¹² = 0.76