Multiple choice

Given: pK1 = 2.0, pK2 = 9.9 and pK3 = 3.9 From the information, calculate the isoelectric pH (pI) of Aspartic acid.

  1. 2.95

  2. 15.8

  3. 7.9

  4. 19.8

  5. 11.9
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A Correct answer
Explanation

For polyfunctional acids, pI is also the pH midway between the pKa values on either side of the isoionic species. For example, the pI for aspartic acid is pI = (pK1 + pK3)/2 = (2.0 + 3.9)/2 = 2.95

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