Question

Consider the titration of a weak acid with a strong base. Which statement below is true regarding the equivalence point in this titration? It occurs at a pH less than 7.0 because a basic salt is formed. O It occurs at a pH greater than 7.0 because an acidic salt is formed. O It occurs at a pH = 7.0 because the acid has been neutralized. O It occurs at a pH less than 7.0 because an acidic salt is formed. O It occurs at a pH greater than 7.0 because a basic salt is formed.

Answer 1

e. It occurs at a pH greater than 7.0 because a basic salt is formed.

We know that when we react an acid with a base, a salt forms. In this case, weak acid is reacting with a strong base to produce the salt to extent of ionization. The salt itself can ionize and reacts again with water to take up protons. Thus, ther are excess OH- ions in the solution causing the solution basic at equivalence point.

Let us consider the titration between NaOH (strong base) and CH3COOH (weak acid).

NaOH + CH3COOH  $\rightleftharpoons$ CH3COO- Na+ + H2O

The titration produces a salt Sodium acetate, CH3COONa.

As the titration continues, some of the acetate ions can react again with water to convert into acetic acid leaving excess OH- ions in the solution.

CH3COO- + H2O  $\rightleftharpoons$ CH3COOH + OH-

Thus, due to the presence of this excess hydroxide ions, we can say that there is a basic salt in the solution.