Lecture Tin covers the following points:-
- Precipitation titration
- Indicators
The formation of a precipitate can be used as the basic of a titration.
Volumetric method based on the formation of a slightly soluble product are Precipitation Titrations
Solubility Rules
1- All common salts of alkali metal are soluble.
2- Acetates, chlorates, nitrates, nitrites, perchlorate are soluble and silver nitrites is insoluble.
3- Cl, Br, I, SCN, of most cations are soluble except Cu, Pb, Hg.
4- Sulfate, thiosulfate are soluble except Sr, Ba, Pb, silver thiosulfate, mercuric sulfate are insoluble.
5-Arsenate, arsenite, borate, carbonate, chromate, cyanide, oxalte, phosphate, sulfite are insoluble except for those of alkali metal.
6- Hydroxide of alkali metal are soluble.
7- The floride of all metal cations are insoluble except for ammonium. silver, mercury and alkali metal cations.
AgX = Ag+ + X-
K = [Ag + ] [ Cl - ] / [ AgCl ]
[AgCl] = 1
because AgCl is present as a pure solid
( ionic concentration are small)
K sp = [Ag + ] [ Cl - ]
Where K sp is called the solubility product
Argentometric method.
1- The ppt must be practically insoluble.
2- Precipitation should be instantaneous.
3- The results of titration should not be effected by adsorption.
4- The end point should be easily detected.
5- At equivalent point
K sp = [Ag + ] [ Cl - ]
Where K sp is called the solubility product
Chemical Indicators for Precipitation Titrations
Formation of a colored precipitate ( Mohr Method )
Formation of a colored complex ( Volhard Method )
Adsorption Indicators Method ( The Fajans Method
- Precipitation titration
- Indicators
The formation of a precipitate can be used as the basic of a titration.
Volumetric method based on the formation of a slightly soluble product are Precipitation Titrations
Solubility Rules
1- All common salts of alkali metal are soluble.
2- Acetates, chlorates, nitrates, nitrites, perchlorate are soluble and silver nitrites is insoluble.
3- Cl, Br, I, SCN, of most cations are soluble except Cu, Pb, Hg.
4- Sulfate, thiosulfate are soluble except Sr, Ba, Pb, silver thiosulfate, mercuric sulfate are insoluble.
5-Arsenate, arsenite, borate, carbonate, chromate, cyanide, oxalte, phosphate, sulfite are insoluble except for those of alkali metal.
6- Hydroxide of alkali metal are soluble.
7- The floride of all metal cations are insoluble except for ammonium. silver, mercury and alkali metal cations.
AgX = Ag+ + X-
K = [Ag + ] [ Cl - ] / [ AgCl ]
[AgCl] = 1
because AgCl is present as a pure solid
( ionic concentration are small)
K sp = [Ag + ] [ Cl - ]
Where K sp is called the solubility product
Argentometric method.
1- The ppt must be practically insoluble.
2- Precipitation should be instantaneous.
3- The results of titration should not be effected by adsorption.
4- The end point should be easily detected.
5- At equivalent point
K sp = [Ag + ] [ Cl - ]
Where K sp is called the solubility product
Chemical Indicators for Precipitation Titrations
Formation of a colored precipitate ( Mohr Method )
Formation of a colored complex ( Volhard Method )
Adsorption Indicators Method ( The Fajans Method