Equilibrium :  Solubility Equilibrium
Solubility equilibrium is base on the assumption that solids dissolve in water to give the basic particles from which they are formed.
  • Molecular solids dissolve to give individual aqueous molecules.
  • Ionic solids dissociate to give their respective positive and negative ions:
  • The ions in formed from the dissociation of ionic solids can carry an electrical current.  Salt solutions, therefore, are good conductors of electricity.  Molecular solids, however, do not dissociate in water to give ions, so no electrical current can be carried.


    1. The ratio of the maximum amount of solute to the volume of solvent in which this solute can dissolve.
      1. Generally expressed in two ways:
        1. grams of solute per 100 g of water
        2. moles of solute per Liter of solution
    Soluble: Dissolve - Do NOT form a solid precipitate.
    1. **alkali metal ions and ammonium ion: Li+, Na+, K+, NH4+ 
    2. acetate ion: C2H3O21- 
    3. nitrate ion: NO31- 
    4. halide ions (X): Cl-, Br-, I-  (Exceptions:  AgX, HgX, and PbX2 are insoluble) 
    5. sulfate ion: SO42-  (Exceptions:  SrSO4, BaSO4, and PbSO4 are insoluble;

    6.                      AgSO4, CaSO4, and Hg2SO4 are slightly soluble) 
    Insoluble: Do NOT Dissolve - Do form a solid precipitate.
    1. carbonate ion: CO32- 
    2. chromate ion: CrO42- 
    3. phosphate ion: PO43- 
    4. sulfide ion: S2-  (Exceptions:  CaS, SrS, and BaS are soluble) 
    5. hydroxide ion: OH-  (Exceptions:  Sr(OH)2 and Ba(OH)2 are soluble; 

    6.                      Ca(OH)2 is slightly soluble)