Question

What assumptions do we make in order to use the Henderson-Hasselbalch equation? a. Both the weak acid and its conjugate base are present initially. b. x (or the change in the reaction) is approximately zero, that is we use the weak acid approximation. c. The final and initial concentration of the acid and it's conjugate base are approximately equal, that is we use the weak acid approximation. d. We only have the weak acid initially.

Answer 1

The final and initial concentration of the acid and it's conjugate base are approximately equal, that is we use the weak acid approximation.

Step-by-step explanation:

The Henderson-Hasselbalch is used to calculate the pH of a buffer solution. It depends on the weak acid approximation.

Since the weak acid ionizes only to a small extent, then we can say that [HA] ≈ [HA]i

Where [HA] = final concentration of the acid and [HA]i = initial concentration of the acid.

It also follows that [A^-] ≈ [A^-]i where [A^-] and[A^-]i refer to final and initial concentrations of the conjugate base hence the answer above.