What is the PH of a Serine Solution in Which

Question

What is the pH of a serine solution in which the α−amine group (pKa9.2) is 33% deprotonated?
A) 8.7
B) 8.9
C) 9.0
D) 9.5
E) 9.8

Accepted Answer

The pH of the solution can be calculated using the Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]), where [A-] is the concentration of the deprotonated form and [HA] is the concentration of the protonated form. Given that the α-amine group is 33% deprotonated, the ratio of [A-]/[HA] is 0.33/0.67. Plugging these values into the equation with the pKa of 9.2 gives: pH = 9.2 + log(0.33/0.67) = 8.9.

What is the pH of a serine solution in which the α−amine group (pKa 9.2) is 33% deprotonated?

What is the pH of a serine solution in which the α−amine group (pK_a 9.2) is 33% deprotonated?