Anonymous
Apr 26
Explain the difference between the mohr, Fajan and Volhard methods ?
as used in determination of Chloride content in samples?
1 view
1 view
2 answers
Sort By
ChatGPT
Apr 26
The Mohr method, Fajan method, and Volhard method are all techniques used in analytical chemistry to determine the concentration of a particular substance in a solution.
1. Mohr method: The Mohr method is a titration method used to determine the concentration of chloride ions in a solution. It involves the use of a silver nitrate solution as the titrant and a potassium chromate indicator to detect the endpoint of the titration. The silver ions react with the chloride ions in the solution to form a white precipitate of silver chloride. The endpoint is reached when all the chloride ions have reacted with the silver ions, causing a red-brown color change in the solution.
2. Fajan method: The Fajan method is a titration method used to determine the concentration of halide ions in a solution. It involves the use of a silver nitrate solution as the titrant and a dichlorofluorescein indicator to detect the endpoint of the titration. The silver ions react with the halide ions in the solution to form a precipitate of silver halide. The endpoint is reached when all the halide ions have reacted with the silver ions, causing a color change in the solution.
3. Volhard method: The Volhard method is a titration method used to determine the concentration of chloride ions in a solution. It involves the use of a silver nitrate solution as the titrant and a ferric ammonium sulfate indicator to detect the endpoint of the titration. The silver ions react with the chloride ions in the solution to form a white precipitate of silver chloride. The endpoint is reached when all the chloride ions have reacted with the silver ions, causing a color change in the solution.
In summary, the Mohr method is specifically used for chloride ions, the Fajan method is used for halide ions, and the Volhard method is also used for chloride ions but with a different indicator. Each method has its own specific application and indicator for detecting the endpoint of the titration.
1. Mohr method: The Mohr method is a titration method used to determine the concentration of chloride ions in a solution. It involves the use of a silver nitrate solution as the titrant and a potassium chromate indicator to detect the endpoint of the titration. The silver ions react with the chloride ions in the solution to form a white precipitate of silver chloride. The endpoint is reached when all the chloride ions have reacted with the silver ions, causing a red-brown color change in the solution.
2. Fajan method: The Fajan method is a titration method used to determine the concentration of halide ions in a solution. It involves the use of a silver nitrate solution as the titrant and a dichlorofluorescein indicator to detect the endpoint of the titration. The silver ions react with the halide ions in the solution to form a precipitate of silver halide. The endpoint is reached when all the halide ions have reacted with the silver ions, causing a color change in the solution.
3. Volhard method: The Volhard method is a titration method used to determine the concentration of chloride ions in a solution. It involves the use of a silver nitrate solution as the titrant and a ferric ammonium sulfate indicator to detect the endpoint of the titration. The silver ions react with the chloride ions in the solution to form a white precipitate of silver chloride. The endpoint is reached when all the chloride ions have reacted with the silver ions, causing a color change in the solution.
In summary, the Mohr method is specifically used for chloride ions, the Fajan method is used for halide ions, and the Volhard method is also used for chloride ions but with a different indicator. Each method has its own specific application and indicator for detecting the endpoint of the titration.
0
Google Gemini AI
Apr 26
Mohr Method
- Principle: Precipitation of Cl⁻ as AgCl in neutral solution, using a chromate indicator (K2CrO4).
- Indicator: K2CrO4. Reddish-brown colored.
- End point: Appearance of a brick-red precipitate (Ag2CrO4) when all Cl⁻ has reacted.
- Suitable for: Dilute to slightly concentrated chloride solutions.
Fajan Method
- Principle: Precipitation of Cl⁻ as AgCl in slightly acidic solution, using fluorescein indicator.
- Indicator: Fluorescein. Yellowish-green colored.
- End point: Adsorption of AgCl particles onto the indicator, turning the solution pink.
- Suitable for: Dilute to moderately concentrated chloride solutions.
Volhard Method
- Principle: Addition of excess AgNO3 to the chloride solution, precipitation of AgCl, and back titration of excess Ag⁺ with NH4SCN.
- Indicator: None.
- End point: Formation of a ferrithiocyanate complex (FeSCN²⁺), indicated by a reddish color.
- Suitable for: Concentrated chloride solutions where the Mohr and Fajan methods are not sensitive enough.
Key Differences
| Feature | Mohr Method | Fajan Method | Volhard Method |
|---|---|---|---|
| Indicator | K2CrO4 | Fluorescein | None |
| Solution pH | Neutral | Slightly acidic | Acidic |
| Precipitation | AgCl in neutral solution | AgCl in acidic solution | AgCl in acidic solution |
| Titration | Direct titration | Direct titration | Back titration |
| Sensitivity | Less sensitive | More sensitive | Highly sensitive |
| Suitable Concentration | Dilute to slightly concentrated | Dilute to moderately concentrated | Concentrated |
- Principle: Precipitation of Cl⁻ as AgCl in neutral solution, using a chromate indicator (K2CrO4).
- Indicator: K2CrO4. Reddish-brown colored.
- End point: Appearance of a brick-red precipitate (Ag2CrO4) when all Cl⁻ has reacted.
- Suitable for: Dilute to slightly concentrated chloride solutions.
Fajan Method
- Principle: Precipitation of Cl⁻ as AgCl in slightly acidic solution, using fluorescein indicator.
- Indicator: Fluorescein. Yellowish-green colored.
- End point: Adsorption of AgCl particles onto the indicator, turning the solution pink.
- Suitable for: Dilute to moderately concentrated chloride solutions.
Volhard Method
- Principle: Addition of excess AgNO3 to the chloride solution, precipitation of AgCl, and back titration of excess Ag⁺ with NH4SCN.
- Indicator: None.
- End point: Formation of a ferrithiocyanate complex (FeSCN²⁺), indicated by a reddish color.
- Suitable for: Concentrated chloride solutions where the Mohr and Fajan methods are not sensitive enough.
Key Differences
| Feature | Mohr Method | Fajan Method | Volhard Method |
|---|---|---|---|
| Indicator | K2CrO4 | Fluorescein | None |
| Solution pH | Neutral | Slightly acidic | Acidic |
| Precipitation | AgCl in neutral solution | AgCl in acidic solution | AgCl in acidic solution |
| Titration | Direct titration | Direct titration | Back titration |
| Sensitivity | Less sensitive | More sensitive | Highly sensitive |
| Suitable Concentration | Dilute to slightly concentrated | Dilute to moderately concentrated | Concentrated |
0
