Solubility Product Constant (Ksp)

Solubility  Product Constant (Ksp):
simply the measure of solubility
The product of equilibrium concentrations
 of  positive and negative ions in a
 saturated solution of a dissolved salt
is called solubility product constant.

Ag Cl (s)   ⥨   Ag+ +  Cl– 
Consider a saturated solution of a sparingly soluble salt AgCl . A dynamic equilibrium is established b/w the undissolved salt & its dissociated positive &negative ions in the solution. i.e.

Ag Cl (s)  ⥨   Ag+ +  Cl
From law of mass action , we have 
Kc =  [Ag+] [ Cl- ]/ [ AgCl ]
Kc  [AgCl ] [Ag+] [ Cl- ]
Kc x K [Ag+] [ Cl- ]
Ksp [Ag+] [ Cl- ]
 As Ag Cl is a solid  & its concentration
 remains constant due to very
light dissociation, so we can write as:

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