Theory of Determination of Chloride In Water Virtual Lab
Precipitimetry: It is a volumetric method of analysis that involves the formation of a practically insoluble salt using a precipitating agent.
Solubility product (Ksp): In a saturated solution of a sparingly soluble electrolytes, the product of molar concentration of ions each raised to a power equal to the number of ions produced is constant at room temperature and pressure.
Ksp of AnBm =[A]n[B]m
N.B: Substance with low Ksp precipitate first.
Conditions required for a Preciptimetric reactions:
1) The precipitate must be practically insoluble.
2) Rapid precipitation.
3) Ease of detection of the endpoint.
Endpoint detection in Precipitimetry.
Determination of Chloride In Water Experiment Principle of Work
Volhard’s method (Formation of colored complex):
- q Direct: Ag+ ions titrated by thiocyante using ferric alum as indicator, End point: First faint red color.
- q Indirect: Known excess standard AgNO3 precipitate halides, cyanide, phosphate then back titrate excess unreacted AgNO3 by thiocyante using ferric alum as indicator, End point: First faint red color.
Here in determination of chloride concentration of water sample experiment we are using the indirect Volhard’s method (back titration):
- In Acidic medium (pH 1-3).
- Known excess standard AgNO3 precipitate chloride, then back titrate excess unreacted AgNO3 by thiocyante using ferric alum as indicator.
- End point: First faint red color.
Ag+ +Cl- → AgCl
Fe3+ +2SCN- → [Fe(SCN)2]+ (blood red colour)
1_22_2022_11_21_58_AM.jpg)
