Oxidation-reduction (redox) titrations are a type of volumetric analysis in which the analyte reacts with a titrant through a transfer of electrons (oxidation and reduction). They are widely used to determine oxidizing or reducing agents in a solution.
Principle:
- Redox titrations are based on a stoichiometric electron transfer between the analyte and titrant.
- One substance gets oxidized (loses electrons) and the other gets reduced (gains electrons).
- The end point is detected by either a suitable indicator that changes color due to the redox reaction, or by self-indicating reactions where the solution changes color naturally.
Procedure:
- Preparation:
- Prepare the analyte solution and a standard solution of the titrant with known concentration.
- Reaction:
- Add the titrant gradually to the analyte until the redox reaction is complete.
- Detection of End Point:
- Use a redox indicator (e.g., starch, ferroin) or rely on a color change of the reactants themselves.
- Calculation:
- Measure the volume of titrant used and calculate the amount of analyte using the stoichiometric relationship between the oxidizing and reducing agents.
Examples of Redox Titrations:
- Permanganometry: Potassium permanganate (KMnO₄) as a titrant; self-indicating due to its purple color.
- Iodometry/Iodimetry: Using iodine or thiosulfate solutions to determine oxidizing or reducing agents.
- Dichrometry: Using potassium dichromate (K₂Cr₂O₇) to estimate iron or other reducing agents.
Applications:
- Determining metal ions like iron, copper, and manganese.
- Estimating oxidizing or reducing agents in water, food, and industrial samples.
- Quality control in pharmaceuticals and chemicals.