how can we find the solubility of molecules in water?
Solubility is the property of a chemical substance to dissolve in a solvent to form a homogeneous solution. We can't find the solubility of molecules, only solubility of substances. Molecules cannot dissolve they can only dissociate.
To find the solubility of the substance we should, first of all, write the dissociation equilibrium equation. For example
AB = An+ + Bn-
Then we have to find the solubility product
Ksp = [An+][Bn-] Ksp is a constant at constant conditions and is taken from the handbook