Definition of Chemical Dissolution

Candela Rocío Barbisan | Nov. 2021
Chemical engineer

In general, we tend to to think that solutes are only solids that dissolve in a liquid solvent, but this is not necessarily the case, since a solute can come from a solution concentrate of said product, from which a certain volume is taken and water is added to make the new solution more dilute. In this case, the solute will be the species contained in the concentrated solution to be diluted and the solvent is water again.

From this concept, different ways of naming solutions arise: diluted or concentrated, when the quantity of solute incorporated is insignificant with respect to the amount of solvent, it is called dilute solution and, conversely, it is a

It is important to note that there is a limit to the amount of solute that we can dissolve in a certain solvent, and that is what is called solubility, and it depends on both the solute and the solvent. For example, we could carry out a experiment homemade, if we add just a tablespoon of salt in a glass of water, it will probably dissolve. Now, if we add the entire package of salt in the glass, the same will not happen, that is why, as many times in the industry, it is necessary to know these values, they are tabulated according to the solute and solvent at certain temperatures.

And again, from this last concept it is that solutions can be classified, if the solute and solvent portions are balanced, the solution is saturated and is at its solubility limit whereas, if the amount of solute exceeds the dissolution capacity, it is called a solution oversaturated.

Parameters that affect solubility

There are three factors very important that come into play when carrying out a dissolution: the temperature, pressure and chemical nature. So then... what are we talking about? When we increase the temperature in a system, the solubility of solids and liquids increases, while in the case of gases decreases, since at higher temperatures the bonds that form it tend to break and be removed from the solution. That is why the tabulated solubility values ​​are referenced to a specific temperature and pressure.

In the case of pressure, it is not a variable that affects solids and liquids too much, but it does in the case of gases, since when the pressure increases, the solubility of a gas increases both in one liquid and in another gas.

The last of the factors depends on the forces that act, when two substances have chemical natures or intermolecular forces similar to each other, they will tend to be more soluble in each other. An example of them is water and oil, if we mix a small portion of oil in water, we will see that it does not dissolve in water, but rather is differentiated into two phases, this occurs because oil is an apolar substance, while water is polar, so it becomes insoluble in Water. This is not the case of you go out, which have dipole moments that make their chemical nature compatible with the polarity of water molecules and can dissolve. In general, we can say that most of the salts are soluble in water while most of the organic compounds (nonpolar) are insoluble in water, except for some alcohols such as ethanol and methanol.

Energy involved in a solution

Finally, when a solute dissolves in a solvent, it can either be released or absorbed. Energy. If the dissolution process releases energy, it is said to be an exothermic process. On the contrary, if this process involves an absorption of energy from the surroundings, then the process is endothermic. The heat put into play is the "heat of dissolution."