Prediction Ionic Solubility

Solubility is difficult to predict with confidence. The most reliable way to obtain a substance’s solubility is to look it up on a table of physical properties in a reference book. When that is not possible, you can use the following guidelines for predicting whether some substances are soluble or insoluble in water. They are summarized in the table below .

  • Ionic compounds with group 1 (or 1A) metallic cations or ammonium cations, NH4+, form soluble compounds no matter what the anion is.

  • Ionic compounds with acetate, C2H3O2-, or nitrate, NO3-, ion form soluble compounds no matter what the cation is.

  • Compounds containing the chloride, Cl-, bromide, Br-, or iodide, I-, ion are water‑soluble except with silver ions, Ag+ and lead(II) ions, Pb2+.

  • Compounds containing the sulfate ion, SO42-, are water‑soluble except with barium ions, Ba2+, and lead(II) ions, Pb2+.

  • Compounds containing carbonate, CO32-, phosphate, PO43-, or hydroxide, OH-, ions are insoluble in water except with group 1 metallic ions and ammonium ions.