When the partially soluble salts like AgCl, CuS, BaSO4, etc are kept in water then a fraction of them dissolved but ionized almost completely.
When AgCl is kept in water then it almost completely ionized as,
AgCl = Ag + + Cl–
By applying law of mass action,
Keq = [ Ag + ] [Cl –] / [AgCl ]
Where, Keq = Equilibrium constant
Keq . [ AgCl ] = [Ag+] [Cl–]
Ksp = [Ag+] [Cl–] ……….(1)
Where, Keq . [ AgCl ] = Ksp = called as solubility product constant.
Hence, the solubility product is defined as the product of the molar concentration of ions in its saturated solution. The product of the molar concentration of ions simply is the ionic product.
Depending upon the values of Ksp and Kip the solution can be divided into three types;
- If Ksp = Kip this solution is said to be saturated.
- Ksp > Kip this solution is called unsaturated.
- Ksp < Kip this solution is called supersaturated.
Depending upon the values of Ksp and Kip .it is possible to predict whether the precipitation will occur or not.
If Ksp < Kip the precipitation will occur others wise not.