🔬 Iodometry vs. Iodimetry: Understanding the Key Differences
When it comes to redox titrations, two important analytical techniques involving iodine are often discussed: iodometry and iodimetry. While they both involve iodine chemistry, they differ in terms of methodology and application. Let’s break down the key differences.
⚗️ Keyword 1: Role of Iodine
- Iodometry: Iodine is not the titrant. It is produced in the reaction by the oxidation of iodide (I⁻) and then titrated.
- Iodimetry: Iodine (I₂) is used directly as the titrant.
✅ In iodometry, iodine is formed during the reaction. In iodimetry, iodine is added to the analyte.
🧪 Keyword 2: Analyte Type
- Iodometry is used to determine oxidizing agents. Ex: Cu²⁺, Fe³⁺, ClO₃⁻
- Iodimetry is used to determine reducing agents. Ex: Ascorbic acid, SO₃²⁻
⚖️ Keyword 3: Titration Process
- Iodometry: The analyte oxidizes iodide (I⁻) to iodine (I₂), and the liberated iodine is titrated with sodium thiosulfate (Na₂S₂O₃). I₂ + 2 S₂O₃²⁻ → 2 I⁻ + S₄O₆²⁻
- Iodimetry: A known amount of iodine is directly titrated against a reducing substance.
🧴 Keyword 4: Indicator
- Starch solution is commonly used as an indicator in both methods.
- It forms a blue-black complex with free iodine.
- Added near the endpoint to avoid formation of tightly bound complexes early in the titration.