Presented are various aspects of solubility and solubility curves, saturation, and supersaturation: understanding what they are and how they are related by looking at the particle level and how different conditions are represented graphically, including comparison to the macro level: 1) solubility and the solubility curve, 2) saturation, 3) equilibrium in saturated solution: what does it look like at the macro versus micro levels, and what is the difference between being saturated at solubility and saturated above solubility, 4) energy considerations in supersaturated solution, 5) comparison of solubility curves of solids versus gases, 6) the significance of oxygen's decreasing solubility for ocean life.
From Wikipedia, 2020:
Solubility is the property of a solid, liquid or gaseous chemical substance called solute to dissolve in a solid, liquid or gaseous solvent. The solubility of a substance fundamentally depends on the physical and chemical properties of the solute and solvent as well as on temperature, pressure and presence of other chemicals (including changes to the pH) of the solution. The extent of the solubility of a substance in a specific solvent is measured as the saturation concentration, where adding more solute does not increase the concentration of the solution and begins to precipitate the excess amount of solute.
Insolubility is the inability to dissolve in a solid, liquid or gaseous solvent.
Most often, the solvent is a liquid, which can be a pure substance or a mixture. One may also speak of solid solution, but rarely of solution in a gas (see vapor-liquid equilibrium instead).
Under certain conditions, the equilibrium solubility can be exceeded to give a so-called supersaturated solution, which is metastable.[1] Metastability of crystals can also lead to apparent differences in the amount of a chemical that dissolves depending on its crystalline form or particle size. A supersaturated solution generally crystallises when 'seed' crystals are introduced and rapid equilibration occurs. Phenylsalicylate is one such simple observable substance when fully melted and then cooled below its fusion point.
Solubility is not to be confused with the ability to dissolve a substance, because the solution might also occur because of a chemical reaction. For example, zinc dissolves (with effervescence) in hydrochloric acid as a result of a chemical reaction releasing hydrogen gas in a displacement reaction. The zinc ions are soluble in the acid.
The solubility of a substance is an entirely different property from the rate of solution, which is how fast it dissolves. The smaller a particle is, the faster it dissolves although there are many factors to add to this generalization.
Crucially, solubility applies to all areas of chemistry, geochemistry, inorganic, physical, organic and biochemistry. In all cases it will depend on the physical conditions (temperature, pressure and concentration) and the enthalpy and entropy directly relating to the solvents and solutes concerned. By far the most common solvent in chemistry is water which is a solvent for most ionic compounds as well as a wide range of organic substances. This is a crucial factor in acidity and alkalinity and much environmental and geochemical work.
A solution is a special type of homogeneous mixture composed of two or more substances. In such a mixture, a solute is a substance dissolved in another substance, known as a solvent. The mixing process of a solution happens at a scale where the effects of chemical polarity are involved, resulting in interactions that are specific to solvation. The solution usually has the state of the solvent when the solvent is the larger fraction of the mixture, as is commonly the case. One important parameter of a solution is the concentration, which is a measure of the amount of solute in a given amount of solution or solvent. The term "aqueous solution" is used when one of the solvents is water.
Gas in liquid:
Oxygen in water
Carbon dioxide in water - a less simple example, because the solution is accompanied by a chemical reaction (formation of ions). The visible bubbles in carbonated water are not the dissolved gas, but only an effervescence of carbon dioxide that has come out of solution; the dissolved gas itself is not visible since it is dissolved on a molecular level.
Liquid in liquid:
The mixing of two or more substances of the same chemistry but different concentrations to form a constant. (Homogenization of solutions)
Alcoholic beverages are basically solutions of ethanol in water.
Solid in liquid:
Sucrose (table sugar) in water
Sodium chloride (NaCl) (table salt) or any other salt in water, which forms an electrolyte: When dissolving, salt dissociates into ions.
Solutions in water are especially common, and are called aqueous solutions.
Non-aqueous solutions are when the liquid solvent involved is not water.
30 май 2020
