When 99% of the glycine is in its -NH₃⁺ form (see question 9), what is the numerical relation between the pH of the solution and the pKa of the amino group?

Group of answer choices

pH = pKa - 2

pH = pKa - 1

pH = pKa +1

None of the answers is correct

question 9:

The amino acid glycine is often used as the main ingredients of a buffer in biochemical experiments. The amino group of glycine, which has a pKa of 9.6, can exist either in the protonated (-NH₃⁺) or as the free base (-NH₂), because of the reversible equilibrium: R-NH₃⁺ R-NH₂ + H⁺

In what pH range can glycine be used as an effective buffer due to its amino group?

Group of answer choices

8.6-10.6

8.6-9.6

9.6-10.6

7.6-8.6