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Solvation or dissolution is a kinetic process and is quantified by its rate. Solubility quantifies the dynamic equilibrium state achieved when the rate of dissolution equals the rate of precipitation. The consideration of the units makes the distinction clearer. The typical unit for dissolution rate is mol/s.
The integral heat of dissolution is defined as a process of obtaining a certain amount of solution with a final concentration. The enthalpy change in this process, normalized by the mole number of solute, is evaluated as the molar integral heat of dissolution. Mathematically, the molar integral heat of dissolution is denoted as:
In a dissolution process, a solute is changed from a pure phase—solid, liquid, or gas—to a solution phase. If the pure phase of the solute is a solid or gas (presuming the solvent itself is liquid), the process can be seen in two stages: the phase change into a liquid, and the mixing of liquids. The dissolution process is generally ...
Example of a dissolved solid (left) Formation of crystals in a 4.2 M ammonium sulfate solution. The solution was initially prepared at 20 °C and then stored for 2 days at 4 °C. In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent.
An example where Henry's law is at play is the depth-dependent dissolution of oxygen and nitrogen in the blood of underwater divers that changes during decompression, going to decompression sickness. An everyday example is carbonated soft drinks , which contain dissolved carbon dioxide.
A solubility equilibrium exists when a chemical compound in the solid state is in chemical equilibrium with a solution containing the compound. This type of equilibrium is an example of dynamic equilibrium in that some individual molecules migrate between the solid and solution phases such that the rates of dissolution and precipitation are equal to one another.
The example of dinitrogen tetroxide (N 2 O 4) dissociating to nitrogen dioxide (NO 2) will be taken. N 2 O 4 ↽ − − ⇀ 2 NO 2 {\displaystyle {\ce {N2O4 <=> 2NO2}}} If the initial concentration of dinitrogen tetroxide is 1 mole per litre , this will decrease by α at equilibrium giving, by stoichiometry, α moles of NO 2 .
Dissolution of small crystals or sol particles and the redeposition of the dissolved species on the surfaces of larger crystals or sol particles was first described by Wilhelm Ostwald in 1896. [ 4 ] [ 5 ] For colloidal systems, Ostwald ripening is also found in water-in-oil emulsions , while flocculation is found in oil-in-water emulsions.