Potentiometric titration, also known as pH titration, is a technique used to determine the concentration of an unknown acid or base by monitoring the change in pH during the titration. It involves measuring the potential (voltage) of an electrochemical cell, such as a pH electrode, as the titrant is added to the analyte solution.

Here's a simplified example of potentiometric titration:

Example: Titration of a Strong Acid with a Strong Base

Let's consider the titration of 50 mL of 0.1 M hydrochloric acid (HCl) with 0.1 M sodium hydroxide (NaOH).

1. Preparation:

- Set up a pH meter or a potentiometric titrator with a pH electrode.

- Fill a burette with the NaOH solution.

- Transfer the HCl solution to a beaker.

2. Initial Reading:

- Immerse the pH electrode into the HCl solution.

- Record the initial pH reading.

3. Titration:

- Start adding the NaOH solution from the burette dropwise into the HCl solution while stirring continuously.

- At each addition, wait for the pH reading to stabilize.

- Record the pH reading after each addition of NaOH.

4. Plotting the Titration Curve:

- Plot a graph with pH on the y-axis and the volume of NaOH added (in mL) on the x-axis.

- The resulting curve is called the titration curve.

5. Equivalence Point:

- The equivalence point is the point at which the moles of acid and base are equal, resulting in a neutral solution.

- The equivalence point is indicated by a sharp change in pH or a plateau in the titration curve.

6. Calculations:

- At the equivalence point, the moles of NaOH added are equal to the moles of HCl initially present in the solution.

- Use the volume and concentration of NaOH added at the equivalence point to calculate the concentration of HCl.

In this example, the equivalence point will be reached when the moles of NaOH added are equal to the moles of HCl present in the 50 mL of 0.1 M HCl solution. Since HCl is a monoprotic acid, the moles of HCl can be calculated as:

Moles of HCl = Concentration of HCl × Volume of HCl

Moles of HCl = 0.1 M × 50 mL = 5.0 mmol

At the equivalence point, the number of moles of NaOH added will also be 5.0 mmol. Therefore, the concentration of NaOH can be calculated as:

Concentration of NaOH = Moles of NaOH / Volume of NaOH

Concentration of NaOH = 5.0 mmol / Volume of NaOH

By determining the volume of NaOH required to reach the equivalence point, the exact concentration of HCl in the unknown solution can be calculated.