What is the Difference Between Mohr Volhard and Fajans Method?

The Mohr, Volhard, and Fajans methods are analytical techniques used for precipitation reactions in chemistry. The main differences between these methods are:

1. Mohr Method:

• Reaction between silver ion and halide ion in the presence of chromate indicator.
• Based on the formation of a precipitate using a chromate.
• Potassium chromate is used as an indicator.

1. Volhard Method:

• Reaction between excess silver ions and halide ions.
• Relys on the formation of a complex with thiocyanate ions using an iron(III) ion.
• Ferric ammonium sulfate is used as an indicator.

1. Fajans Method:

• Adsorption reaction between silver halide and fluorescein.
• Involves the adsorption of a colored indicator onto the surface of a precipitate.

In summary, the Mohr method is based on the reaction between silver ion and halide ion in the presence of chromate indicator, the Volhard method refers to the reaction between excess silver ions and halide ions, and the Fajans method involves the adsorption of a colored indicator onto the surface of a precipitate.

Comparative Table: Mohr Volhard vs Fajans Method

Here is a table comparing the Mohr, Volhard, and Fajans methods:

The main difference between the Mohr and Volhard methods is the indicator used and the reaction involved. The Mohr method uses potassium chromate as an indicator and involves the reaction between silver ions and halide ions in the presence of chromate indicator. On the other hand, the Volhard method uses ferric ammonium sulfate as an indicator and involves the reaction between excess silver ions and halide ions, forming a complex with thiocyanate ions.

The Fajans method, on the other hand, is based on the adsorption reaction between silver halide and fluorescein, and it does not use an indicator. This method is used for the determination of halide ions, particularly chloride, bromide, and iodide ions, in a solution.