Mohr’s method in Precipitation titrations
Mohr’s method is a type of precipitation titration used to determine the concentration of chloride ions in a solution. It is based on the reaction between silver nitrate (AgNO3) and chloride ions (Cl-) in an aqueous solution to form a silver chloride (AgCl) precipitate.
The Mohr’s method involves the addition of a known volume of silver nitrate solution of known concentration to the solution containing chloride ions. The silver nitrate is added until all of the chloride ions have reacted, forming a white precipitate of silver chloride. The endpoint of the titration is determined by the formation of this precipitate, which can be observed visually.
To carry out the Mohr’s method, the sample solution containing chloride ions is titrated with a standard solution of silver nitrate using a suitable indicator, such as potassium chromate. The indicator is added to the solution and reacts with the silver ions before the chloride ions, producing a yellow color.
As the titration progresses, the silver ions begin to react with the chloride ions, forming a white precipitate of silver chloride. The endpoint is reached when all the chloride ions have reacted, and the yellow color of the indicator disappears, indicating that all the silver ions have reacted with the chloride ions.
The amount of silver nitrate solution added to the sample can be used to calculate the concentration of chloride ions present in the sample, using stoichiometry of the reaction.
Mohr’s method is widely used in analytical chemistry for the determination of chloride ions in various samples, including drinking water, wastewater, and biological samples. It is a simple, inexpensive, and reliable method for the determination of chloride ions in aqueous solutions. However, it may suffer from some limitations such as interference from other ions in the sample, and the need for careful handling of the silver nitrate solution due to its toxicity and light sensitivity.
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