Final answer:
The equivalence point between a strong acid and a weak base is below pH 7 because the reaction produces a weak acid, which only partially dissociates, resulting in an acidic solution.
Step-by-step explanation:
The equivalence point between a strong acid and a weak base is typically below pH 7 because the reaction results in the formation of a weak acid. Strong acids completely dissociate in water to give a high concentration of hydrogen ions (H+), whereas weak bases only partially accept hydrogen ions. When titrating a weak base with a strong acid, the weak base is converted to its conjugate acid upon reaction. Because this conjugate acid is weak, it will partially dissociate to produce H+, results in an acidic solution at the equivalence point.
In the simplest case, when a strong acid reacts with a strong base, they neutralize each other, and the resulting solution is neutral with a pH of 7. However, when a weak base is titrated with a strong acid, the resulting solution at the equivalence point contains the conjugate acid of the weak base, which is not fully neutral, and thus the solution remains acidic, indicating a pH of less than 7.