Question

According to the Henderson–Hasselbalch equation, when the pH of a solution of histidine is 1.85, what is the ratio of the carboxylic acid form of the molecule to its conjugate base (the carboxylate form)? [For practice, either use Marvin Sketch or a piece of paper to draw the acid and conjugate base.]1 or 4?

Answer 1

The ratio of the carboxylic acid form of histidine to its conjugate base is 1:10^4 (10,000:1).

Step-by-step explanation:

The Henderson-Hasselbalch equation is used to calculate the ratio of the acid form to the conjugate base form of a molecule in a solution. The equation is pH = pKa + log([A-]/[HA]), where pH is the desired pH of the solution, pKa is the acid dissociation constant of the molecule, and [A-] and [HA] are the concentrations of the conjugate base and acid, respectively.

In this case, the pH of the solution is given as 1.85. To calculate the ratio, we can substitute the values into the Henderson-Hasselbalch equation. Since the equation implies a logarithmic relationship, we need to take the antilogarithm of the solution side to find the ratio.

The ratio of the carboxylic acid form of histidine to its conjugate base is 1:104 (10,000:1).