Question

Sketch the general appearance of the curve for the titration of a weak base with a strong acid. What chemistry governs the ${}^{\mathbf{pH}}$in each of the four distinct regions of the curve?

Short answer

The general appearance of the curve for the titration of a weak base with a strong acid.

Step-by-step solution

Determining the general appearance of curve for the titration.

• The volume of titrant (of known concentration) that reacts with an acid or base in a stoichiometric proton-transfer reaction is used to determine the concentration of an acid or base. Theory Strong or weak acids or bases are used in acid-base titrations.

• In an acid-base titration, moles of base equal moles of acid, and the solution contains only salt and water.

Representing the titration curve.

The titration curve for the titration of a weak base with a strong acid look like

Determining the regions on the titration curve.

As we can see on the titration curve, there are four regions on it:

1. Before any acid is added, the solution only contains the weak base and the ${}^{\mathbf{pH}}$is calculated by solving the base hydrolysis equation.

2. Before the equivalence point, the solution contains a buffer consisted of a weak base and a strong acid and ${}^{\mathbf{pH}}$is calculated by solving the Henderson-Hasselbalch equation.

3. At the equivalence point the base has been converted to a weak acid and the${}^{\mathbf{pH}}$ is calculated by solving the acid hydrolysis equation.

4. After the equivalence point there is only strong acid in the solution and the ${}^{\mathbf{pH}}$is determined by the concentration of the acid.