Consider the curve shown here for the titration of a weak monoprotic acid with a strong base and answer each question.
d. At what volume of added base is the pH calculated by working an equilibrium problem based on the concentration and K_b of the conjugate base?

Key Concepts

Weak Acid and Strong Base Titration

In a titration involving a weak monoprotic acid and a strong base, the weak acid partially dissociates in solution, leading to a gradual increase in pH as the base is added. The equivalence point occurs when the amount of base added neutralizes the acid, resulting in a solution primarily of the conjugate base. Understanding this process is crucial for determining the pH at various points during the titration.

Equilibrium and Kb

The equilibrium constant for the base, Kb, is a measure of the strength of the conjugate base formed from the weak acid. When calculating pH at a specific volume of added base, one must consider the equilibrium established between the conjugate base and water, which involves the dissociation of the base and the concentrations of the species in solution. This concept is essential for accurately determining pH in the context of titration.

Henderson-Hasselbalch Equation

The Henderson-Hasselbalch equation relates the pH of a solution to the pKa of the weak acid and the ratio of the concentrations of the conjugate base to the weak acid. This equation is particularly useful in titration scenarios, especially after the equivalence point, where the pH can be calculated based on the concentration of the conjugate base and its Kb. It provides a straightforward method for estimating pH in buffer solutions formed during the titration.