A potentiometric titration is a type of titration where the endpoint is determined by measuring the change in electric potential (voltage) of the solution instead of using a color indicator. Here’s a explanation:
Basic Idea
- Every solution has an electrode potential depending on the ions present.
- During a titration, as the reaction progresses, the concentration of ions changes, which changes the electrical potential.
- By monitoring this potential with a sensitive voltmeter or a potentiometer, we can detect the equivalence point.
How It Works
- Setup:
- Two electrodes are placed in the solution:
- Indicator electrode: Sensitive to the ion being titrated.
- Reference electrode: Has a constant potential (like a silver/silver chloride electrode).
- The solution is connected to a potentiometer or digital voltmeter.
- Two electrodes are placed in the solution:
- Titration Process:
- The titrant is added gradually.
- The potential (voltage) of the solution is measured after each addition.
- At the equivalence point, there is a sharp change in potential, which signals the completion of the reaction.
Advantages
- No indicator is needed.
- Works well for colored or opaque solutions.
- Very precise, especially for redox titrations.
Common Applications
- Acid-base titrations: Using a pH electrode.
- Redox titrations: Using a platinum or other metal electrode.
- Complexometric titrations: Using selective ion electrodes.
Example
- Redox titration: Titrating Fe²⁺ with Ce⁴⁺:
- Fe²⁺ is oxidized to Fe³⁺.
- The potential changes sharply at the point where all Fe²⁺ is converted.
- That sharp jump indicates the equivalence point.