The titration of a weak acid by a weak base is not a...

The titration of a weak acid by a weak base is not a satisfactory procedure because the pH does not increase sharply at the equivalence point. Demonstrate this fact by sketching a titration curve for the neutralization of $10.00 \mathrm{mL}$ of $0.100 \mathrm{M} \mathrm{CH}_{3} \mathrm{COOH}$ with $0.100 \mathrm{M} \mathrm{NH}_{3}$

Key Concepts

Acid-Base Titration

Acid-base titration is an analytical technique used to determine the concentration of an acid or base by reacting it with a titrant of known concentration. The titration curve, which plots pH versus volume of titrant added, helps in understanding reaction progress and determining key points such as the equivalence point. In weak acid-weak base titrations, the reaction does not exhibit a sharp pH change at the equivalence point, complicating endpoint detection.

Weak Acid and Weak Base

Weak acids and weak bases partially dissociate in solution, meaning that they do not completely convert to their ions. This partial dissociation results in overlapping equilibria when a weak acid is titrated with a weak base, and the resulting pH changes are generally more gradual compared to strong acid-strong base titrations, leading to a less distinct equivalence point.

Equivalence Point

The equivalence point in a titration is reached when the amount of titrant added is stoichiometrically equivalent to the amount of substance being titrated. In weak acid-weak base titrations, the equivalence point is less pronounced because the resulting solution typically contains a salt that is the product of two weak species, which undergoes hydrolysis and exhibits only minor changes in pH near the equivalence point.

Buffer Region

A buffer region in a titration is characterized by a gradual change in pH despite the addition of titrant. This occurs when the solution contains appreciable amounts of both the weak acid and its conjugate base (or weak base and its conjugate acid), creating a resistance to change in pH. In weak acid-weak base titrations, the buffering effect is responsible for the gradual pH change during the titration until the equivalence point is reached.

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