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

Key Concepts

Titration

Titration is a quantitative analytical technique used to determine the concentration of a solute in a solution. In this context, it involves the gradual addition of a strong acid to a weak base, allowing for the observation of pH changes. The equivalence point, where the amount of acid equals the amount of base, is critical for calculating the resulting pH and understanding the acid-base reaction.

Weak Base and Conjugate Acid

A weak base is a substance that partially ionizes in solution, establishing an equilibrium between the base and its conjugate acid. The conjugate acid is formed when the weak base accepts a proton (H+). Understanding the relationship between a weak base and its conjugate acid is essential for calculating pH at various points in the titration, particularly after the addition of acid.

Equilibrium and Ka

Equilibrium in a chemical reaction refers to the state where the rates of the forward and reverse reactions are equal, resulting in constant concentrations of reactants and products. The acid dissociation constant (Ka) quantifies the strength of a weak acid, indicating how well it donates protons in solution. In titration, after a certain volume of acid is added, the pH can be calculated using the equilibrium concentrations and the Ka of the conjugate acid formed.