After the equivalence point, the solution's pH is dominated by:

After the equivalence point, the solution's pH is dominated by:

• A. The leftover HA.
• B. The added base remains unreacted.
• C. The conjugate acid A- forms more HA.
• D. The hydrolysis of the conjugate base A- produces OH- and raises pH.

Answer: (D)

When a weak acid is titrated with a strong base and you pass the equivalence point, the solution is dominated by the conjugate base present in water. This conjugate base reacts with water in a hydrolysis process: A- + H2O ⇌ HA + OH-. This reaction adds hydroxide ions to the solution, raising the pH above 7. The presence of leftover unreacted base can contribute to pH as well, but the fundamental reason the pH is basic after equivalence is that the conjugate base hydrolyzes to produce OH-. If HA were formed instead, it would consume OH- and lower pH, so the hydrolysis of A- is the key driver that raises pH in this context.

When a weak acid is titrated with a strong base and you pass the equivalence point, the solution is dominated by the conjugate base present in water. This conjugate base reacts with water in a hydrolysis process: A- + H2O ⇌ HA + OH-. This reaction adds hydroxide ions to the solution, raising the pH above 7. The presence of leftover unreacted base can contribute to pH as well, but the fundamental reason the pH is basic after equivalence is that the conjugate base hydrolyzes to produce OH-. If HA were formed instead, it would consume OH- and lower pH, so the hydrolysis of A- is the key driver that raises pH in this context.