Amperometric Titration
Introduction
Amperometric titration is a technique used in chemistry to determine the concentration of a analyte in a solution. It is based on the measurement of the current that flows through a solution when a potential is applied. The current is proportional to the concentration of the analyte, so by measuring the current, the concentration of the analyte can be determined.Basic Concepts
Amperometric titration is based on the principle of electrochemistry. When a potential is applied to a solution, ions in the solution will migrate towards the electrode of opposite charge. If the potential is high enough, the ions will be reduced or oxidized at the electrode surface. The current that flows through the solution is proportional to the rate of the redox reaction.The redox reaction that occurs at the electrode surface is called the electrode reaction. The electrode reaction for amperometric titration is typically a one-electron transfer reaction. The following is an example of a one-electron transfer reaction:
Mn+ + e- → M(n-1)+
where M is the metal ion and n is the oxidation state of the metal ion.
The current that flows through the solution is proportional to the rate of the electrode reaction. The rate of the electrode reaction is proportional to the concentration of the analyte, so by measuring the current, the concentration of the analyte can be determined.
Equipment and Techniques
The equipment used for amperometric titration includes a potentiostat, a working electrode, a reference electrode, and a counter electrode. The potentiostat is used to apply a potential to the solution and to measure the current that flows through the solution. The working electrode is the electrode at which the redox reaction occurs. The reference electrode is used to provide a stable reference potential. The counter electrode is used to complete the electrical circuit.The technique for amperometric titration is as follows:
1. A known volume of the analyte solution is added to a titration cell.
2. A potential is applied to the solution and the current is measured.
3. The titrant is added to the solution in small increments.
4. The current is measured after each addition of titrant.
5. The titration is continued until the equivalence point is reached.
The equivalence point is the point at which the moles of titrant added are equal to the moles of analyte present in the solution. At the equivalence point, the current will be zero.
Types of Experiments
There are two types of amperometric titrations: direct titrations and indirect titrations. In direct titrations, the analyte is directly oxidized or reduced at the electrode surface. In indirect titrations, the analyte reacts with a reagent to produce a product that is then oxidized or reduced at the electrode surface.Data Analysis
The data from an amperometric titration can be used to construct a titration curve. A titration curve is a plot of the current versus the volume of titrant added. The equivalence point is the point on the titration curve where the current is zero.The concentration of the analyte can be determined from the titration curve. The concentration of the analyte is equal to the moles of titrant added at the equivalence point divided by the volume of the analyte solution.
Applications
Amperometric titration is a versatile technique that can be used to determine the concentration of a wide variety of analytes. Amperometric titration is often used to determine the concentration of metal ions, but it can also be used to determine the concentration of organic compounds.Amperometric titration is a relatively simple and inexpensive technique. It is also a very accurate and precise technique. Amperometric titration is a valuable tool for chemists and other scientists.