What is the approximate charge difference between glutamic acid and acetic acid at pH 9.5?

To determine the approximate charge difference between glutamic acid and acetic acid at pH 9.5, we first need to understand the concept of pKa. The pKa value represents the acidity of an acid, specifically the pH at which the acid is half dissociated.

In the case of glutamic acid, there are two dissociating groups: the carboxyl group (COOH) and the amino group (NH2). Each group has its own pKa value. The carboxyl group has a pKa value of around 2.2, and the amino group has a pKa value of around 9.6. Acetic acid (CH3COOH) has a pKa value of approximately 4.8.

At low pH levels, below the pKa of the carboxyl group, both glutamic acid and acetic acid exist in their protonated forms, with a positive charge on the nitrogen atom of the amino group. As the pH increases, above the pKa of the carboxyl group, the carboxyl group will start to deprotonate, resulting in a negatively charged carboxylate group (COO-) in both acids.

At pH 9.5, glutamic acid will be almost fully deprotonated, as it is well above the pKa of both the carboxyl group and the amino group. Therefore, glutamic acid will have a net charge of -1, due to the negatively charged carboxylate group.

In the case of acetic acid, at pH 9.5, it will still be mostly protonated, as the pH is significantly below its pKa value. Therefore, acetic acid will have a net charge of approximately 0, as there are no charged functional groups present.

In summary, the approximate charge difference between glutamic acid and acetic acid at pH 9.5 is -1 for glutamic acid and 0 for acetic acid.