Mohr Titration
Definition and meaning of Mohr Titration in chemistry.
Mohr titration is a classical quantitative analytical method used to precisely determine the concentration of chloride or bromide ions in a sample solution using silver nitrate as the titrant.
In more detail
The laboratory technique involves slowly adding a standard solution of silver nitrate to the unknown sample, which immediately precipitates a solid silver halide. A small amount of potassium chromate is always added as a visual chemical indicator. Once all the target chloride or bromide ions have completely reacted, the very first excess drop of silver nitrate reacts with the chromate ions to form a distinct reddish-brown precipitate of silver chromate, clearly signaling the visual endpoint of the titration. The entire process must be carefully carried out in a neutral or very slightly alkaline solution to ensure accuracy.
Key facts
| Field | Analytical Chemistry |
|---|---|
| Titrant | Silver nitrate (AgNO3) |
| Indicator | Potassium chromate (K2CrO4) |
Determining the exact salinity of a brackish water sample by titrating its dissolved chloride content with silver nitrate, using potassium chromate to clearly show the final reddish-brown visual endpoint.
Frequently asked questions
Why must the Mohr titration strictly be performed in a neutral solution?
If the solution is too strongly acidic, the chromate indicator converts to dichromate, preventing the formation of the required red precipitate; if it is too basic, solid silver hydroxide precipitates instead.
What is the specific endpoint color change?
The analytical endpoint is distinctively marked by the sudden appearance of a reddish-brown silver chromate precipitate.