The chloride ion, bromide ion, and iodide ion generally form soluble salts. 4.The sulfate ion generally forms soluble salts. Insoluble Salts 1.Sulfides are usually insoluble. Oxides are usually insoluble. Exceptions include Na 2 O, K 2 O, SrO, and BaO. 3.
Hydroxides are usually insoluble.
Chromates are usually insoluble. Phosphates and carbonates are usually insoluble. The Solubility Product Expression, K sp Silver iodide is classified as an insoluble substance. Only a small amount will dissolve in water. When silver iodide is placed in water, an equilibrium is established.