Which of the above buffers (acetic acid, formic acid, boric acid, ascorbic acid, tris) would be useful if you wished to maintain a pH value of 8.8 in a particular solution? or

Question

Devyn Roth

Chemistry

21 April, 06:49

Which of the above buffers (acetic acid, formic acid, boric acid, ascorbic acid, tris) would be useful if you wished to maintain a pH value of 8.8 in a particular solution? or

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Answers (1)

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Beans · Answer 1

To maintain a pH value of 8.8 in a particular solution the best option is Tris or boric acid.

Explanation:

To decide a good acid/conjugate base pair it is necessary to know the pKa of the acids because every buffer has an optimal effective range due to pH = pKa ± 1. The closer the working pH is to the acid pKa, the buffer will be more effective. Below is the list of the pKa of the different option.

Acetic acid: pKa = 4.76

Boric acid: pKa1 = 9.24 pKa2 = 12.74 pKa3 = 13.80

Ascorbic acid: pKa1 = 4.17 pKa2 = 11.57

Tris: pKa = 8.06

Acetic and Ascorbic acid are too far from the range of 8.8. Thus the best options are boric acid or Tris. To define between these two it is necessary to consider other factors like interaction between components of the solution and the ionic strength required.