![]() If energy changes are not favorable, or without suitable nucleation sites, no precipitation occurs and the solution remain supersaturated. This involves energy changes depending on the dissolution reaction free energy ( endothermic or exothermic process accompanied by an entropy increase) and the relative surface energy developed between the solid and the solution. The creation of a solid particle implies the formation of an interface with the solution. When a potassium iodide solution reacts with a lead(II) nitrate solution, a yellow precipitate of lead(II) iodide is formed.Īn important stage of the precipitation process is the onset of nucleation. When a barium chloride solution reacts with sulphuric acid, a white precipitate of barium sulfate is formed. The formation of a precipitate can be caused by a chemical reaction. Precipitation occurs more rapidly from a strongly supersaturated solution. This can be due to temperature changes, solvent evaporation, or by mixing solvents. The precipitation of a compound may occur when its concentration exceeds its solubility. metallurgy and alloys) when solid impurities segregate from a solid phase. The notion of precipitation can also be extended to other domains of chemistry ( organic chemistry and biochemistry) and even be applied to the solid phases (e.g. The clear liquid remaining above the precipitated or the centrifuged solid phase is also called the supernate or supernatant. In case of an inorganic chemical reaction leading to precipitation, the chemical reagent causing the solid to form is called the precipitant. The solid formed is called the precipitate. In an aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a supersaturated solution. Principle of chemical precipitation in aqueous solution ( Learn how and when to remove this template message) JSTOR ( February 2008) ( Learn how and when to remove this template message).Unsourced material may be challenged and removed.įind sources: "Precipitation" chemistry – news ![]() Please help improve this article by adding citations to reliable sources. (This is why wax is insoluble in water: it is non-polar, so the wax-wax interactions are weak, but the wax-water interactions are weaker than the water-water interactions.This article needs additional citations for verification. (Ionic salts are a good example: usually they have strong interactions in the solid and solvated states.) If the interactions in the solid are weak, the compound can still be insoluble in polar solvents if the interactions with the solvent are weaker than the Coulomb interactions of the solvent molecules with other solvent molecules. For instance, if it has very strong interactions between molecules or ions in the solid state, then it won't be very soluble unless the solvation interations are also very strong. Solubility depends on the relative stability of the solid and solvated states for a particular compound. (It's also a little funny because many salts aren't strong electrolytes, so teachers might be telling their students to write an equation that doesn't show what's really happening.) However, it does help show what it means to be a spectator ion, since they are the same on both sides when you write it like this. No real chemist would be likely to do this because it is a nuisance. ![]()
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