Precipitation reaction is the process where from a solution, after a reaction, it is separate a compound, fully or partially insoluble in the form of crystals, powder, flakes, etc..Thus, at the treatment of a solution of silver nitrate with a solution of sodium chloride silver chloride is precipitated immediately :
AgNO3 + NaCl -> AgCl + NaNO3
A precipitate is a solid very little soluble, formed after the reaction in solution. The reaction of the solution from potassium iodide, KI, with a solution of lead nitrate, Pb (NO3) form a yellow precipitate of lead iodide, PbI2.The precipitate obtained, iodine lead, PbI2, is very slightly soluble in water. Solubility is the maximum amount of a substance which is dissolved in a certain quantity of solvent, at a certain temperature. Very slightly soluble substances are considered soluble electrolytes.
Solubility product is the size which indicates the possibility of ions to move in a heavy soluble form, solubility values of the product explain the formation and dissolution of precipitated solution. Therefore, knowledge of this size has a great importance in choosing the methods for qualitative and quantitative analysis. From the solubility product value can be calculated solubility (S).
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