At the equivalence point, the pH is:

At the equivalence point, the pH is:

• A. Less than 7.
• B. Equal to 7.
• C. Greater than 7.
• D. Determined solely by the base used.

Answer: (C)

At the equivalence point the solution contains the conjugate base (or conjugate acid) formed when the acid is fully neutralized by the base, and its ability to react with water sets the pH. If a weak acid is being titrated with a strong base, the conjugate base produced hydrolyzes water: A- + H2O ⇌ HA + OH-. This generates OH− and pushes the pH above 7, so the pH at equivalence is greater than 7. The exact value depends on how strongly the original acid resisted dissociation (i.e., its Ka) because that determines how basic the conjugate base is. This is why the pH is not fixed at 7 for all titrations and is not determined solely by the base used; strong-strong titrations give pH ≈ 7, while weak-strong titrations yield a basic pH at equivalence.

At the equivalence point the solution contains the conjugate base (or conjugate acid) formed when the acid is fully neutralized by the base, and its ability to react with water sets the pH. If a weak acid is being titrated with a strong base, the conjugate base produced hydrolyzes water: A- + H2O ⇌ HA + OH-. This generates OH− and pushes the pH above 7, so the pH at equivalence is greater than 7. The exact value depends on how strongly the original acid resisted dissociation (i.e., its Ka) because that determines how basic the conjugate base is. This is why the pH is not fixed at 7 for all titrations and is not determined solely by the base used; strong-strong titrations give pH ≈ 7, while weak-strong titrations yield a basic pH at equivalence.