Out of the following, which is the best acid/base to use to prepare a buffer with a pH of 11.00? a. hydrogen peroxide b. phenol c. propylamine What ratio of masses of the weak acid/base and its conjugate should you use to make the buffer of the required pH? Use the sodium salt of the conjugate base if you chose a weak acid or the chloride salt of the conjugate acid if you chose a weak base.

Question

Chemistry

Yahir Cisneros

9 September, 09:34

Out of the following, which is the best acid/base to use to prepare a buffer with a pH of 11.00? a. hydrogen peroxide b. phenol c. propylamine What ratio of masses of the weak acid/base and its conjugate should you use to make the buffer of the required pH? Use the sodium salt of the conjugate base if you chose a weak acid or the chloride salt of the conjugate acid if you chose a weak base.

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Mirabel · Answer 1

Considering the Henderson - Hasselbalch equation for the calculation of the pH of the buffer solution as:

pH=pKa+log[base]/[acid]

Where K is the dissociation constant of the acid.

The weak acid for making the buffer must have a pKa value near to the desired pH of the weak acid.

Propyl amine has pka = 10.71

So, Propyl amine will be the best. It is a base. So, the conjugate will be chloride salt of it.

pH=pKa+log[base]/[acid]

pH = 11.00

pKa = 10.71

So,

log[base]/[acid] = 11.00 - 10.71

[base]/[acid] = 1.95