Potassium chromate is used as an indicator in argentometric titrations because it forms a red precipitate (silver chromate) in the presence of excess silver ions. This color change signals the end point of the titration, where all the chloride ions have reacted with silver ions. This makes it easy to visually detect when the reaction is complete.
Fajan's method of argentometric titration involves the use of potassium chromate as an indicator to detect the end point of a titration between silver ions and chloride ions. The indicator changes color from yellow to red when all the chloride ions have reacted with the silver ions, marking the end point of the titration.
The reaction has to be carried out at neutral conditions because in acid the chromate indicator concentration decreases due to the reaction with the H+ ions, forming HCrO4-. It cannot be in too basic of a solution (greater than 10.5) because then silver hydroxide will form before the silver chromate can form.
When pH is lower than 7, chromic ion gets protonated and chromic acid is predominant in the solution. Consequently, if the pH is above 7, chromate ion concentration is too low to form precipitate with silver ions at the end point. If the pH is above 10, brownish silver hydroxide is formed masking the end point. hence a neutral medium must be maintained
The chemical formula of silver chromate is Ag2CrO4.
Stannic chromate = Tin(IV) chromate = Sn(CrO4)2
Fajan's method of argentometric titration involves the use of potassium chromate as an indicator to detect the end point of a titration between silver ions and chloride ions. The indicator changes color from yellow to red when all the chloride ions have reacted with the silver ions, marking the end point of the titration.
At the end point, so after all Cl- has reacted with Ag+, a brown-red precipitate of silver chromate (Ag2CrO4), is formed. (Argentometric indicator)Description:The solubility of silver chromate is slightly higher than that of silver chloride. So, in a mixture of both ions silver chloride will be formed. Only when no chloride is left silver chromate will be formed and precipitated out.Prior to the endpoint the solution has a milky lemon yellow appearance, due to the color of the chromate ion and the precipitate of silver chloride already formed.When approaching the endpoint, additions of silver nitrate lead to steadily slower disappearing red colorations. When the red brownish color remains (with grayish spots of silver chloride in it) the endpoint of titration is reached. (wikipedia)
In the titration of silver nitrate solution, a precipitation indicator like chloride ion is used to detect the endpoint through the formation of a white precipitate (AgCl). An adsorption indicator like chromate ion can also be used, where the color change of the adsorbed chromate ion on silver chloride indicates the endpoint. Both indicators are effective in detecting the equivalence point in silver nitrate titrations.
The reaction has to be carried out at neutral conditions because in acid the chromate indicator concentration decreases due to the reaction with the H+ ions, forming HCrO4-. It cannot be in too basic of a solution (greater than 10.5) because then silver hydroxide will form before the silver chromate can form.
Iron(II) chromate is a chemical compound with the formula FeCrO4. It is a yellow solid that is sparingly soluble in water. The compound is used in analytical chemistry applications as an indicator for the titration of lead.
The Volhard method is a titration method used to determine the concentration of halide ions in a solution using silver nitrate and potassium chromate as indicators. The Mohr method, on the other hand, is also a titration method used to determine the chloride ions concentration in a solution using silver nitrate and potassium chromate indicators. The key difference lies in the end point detection: Volhard method involves the use of a ferric alum indicator that forms a red-brown precipitate, while the Mohr method involves the formation of a red-brown silver chromate precipitate.
When pH is lower than 7, chromic ion gets protonated and chromic acid is predominant in the solution. Consequently, if the pH is above 7, chromate ion concentration is too low to form precipitate with silver ions at the end point. If the pH is above 10, brownish silver hydroxide is formed masking the end point. hence a neutral medium must be maintained
Cesium Chromate = Cs2CrO4
The chemical formula of silver chromate is Ag2CrO4.
Stannic chromate = Tin(IV) chromate = Sn(CrO4)2
The chemical formula of sodium chromate is Na2CrO4.
The chemical formula for beryllium chromate is BeCrO4.