- Characteristics of non-electrolytes
- Chemical
- Physical
- Examples of non-electrolytes
- Nonpolar gases
- Solvents
- Organic solids
- Final comment
- References
The non - electrolytes are the compounds not dissociate in water or any other polar solvent to generate ions. Its molecules do not dissolve in water, maintaining their original integrity or structure.
The non-electrolytes by not dissociating into ions, electrically charged particles, do not conduct electricity. In this it contrasts with salts, ionic compounds, which, when dissolved in water, do release ions (cations and anions), which help the environment to be a conductor of electricity.
Sugar is an example of what is meant by an electrolytic compound. Source: Marco Verch Professional Photographer and Speaker (https://www.flickr.com/photos//46148146934)
The classic example is made up of the sugar-table salt duo, sugar being a non-electrolyte, while salt is an electrolyte. Sucrose molecules in sugar are neutral, they do not have electrical charges. On the other hand, the Na + and Cl - ions of the salt do have charges, positive and negative, respectively.
The consequence of this is that a sugary solution is unable to light a light bulb in an electrical circuit, unlike a saturated salt solution, which does light the light bulb.
On the other hand, the experiment could be repeated directly with the molten substances. Liquid sugar will not conduct electricity, while molten salt will.
Characteristics of non-electrolytes
Chemical
Non-electrolyte compounds are covalent compounds. This means that they have covalent bonds in their structures. The covalent bond is characterized by being formed by a pair of atoms that have the same or similar electronegativities.
Therefore, the pair of atoms of the covalent bond that share electrons do not separate when they come into contact with water, nor do they acquire a certain charge. Instead, the entire molecule dissolves, keeping its structure unchanged.
Returning to the example of sugar, the water molecules do not have enough energy to break the CC or C-OH bonds of the sucrose molecules. They also cannot break their glycosidic bond.
What the water molecules do do is wrap the sucrose molecules and separate them from one another; distance them, solvate them or hydrate them, until all the sugar crystal disappears in the eyes of the beholder. But the sucrose molecules are still in the water, they just no longer form a visible crystal.
As polar as sucrose molecules are, they lack electrical charges, which is why they do not help electrons move through water.
In summary to the chemical characteristics: non-electrolytes are covalent compounds, which do not dissociate in water, nor do they contribute ions to it.
Physical
Regarding the physical characteristics of a nonelectrolyte, it can be expected that it consists of a nonpolar or low polarity gas, as well as a solid with low melting and boiling points. This is because, because they are covalent compounds, their intermolecular interactions are weaker compared to those of ionic compounds; for example, salts.
Also, they can be liquid, as long as they do not dissociate into ions and keep their molecular integrity intact. Here, the case of liquid sugar is mentioned again, where its sucrose molecules are still present without having suffered the breaking of any of their covalent bonds.
A nonelectrolyte must not be able to conduct electricity regardless of its physical state. If it melts due to the action of temperature, or if it dissolves in water or any other solvent, it must not conduct electricity or contribute ions to the environment.
Salt, for example, in its solid state is non-electrolytic; it does not conduct electricity. However, once melted, or dissolved in water, it does behave like an electrolyte by having its Na + and Cl - ions free to move.
Examples of non-electrolytes
Nonpolar gases
Nonpolar gases, such as oxygen, nitrogen, methane, fluorine, chlorine, carbon monoxide, helium, and other noble gases, do not conduct electricity when "dissolved" in water. This is due in part to their low solubility, and also to the fact that they do not react with water to form acids.
For example, oxygen, O 2, will not dissociate in water to generate free O 2- anions. The same reasoning applies for gases N 2, F 2, Cl 2, CO, etc. These gases are enveloped or hydrated by the water molecules, but without their covalent bonds breaking at any time.
Even if all these gases were counted, they would be unable to conduct electricity because of the total absence of electrical charges in the sinuses of their nonpolar liquids.
However, there are non-polar gases that cannot be classified as non-electrolyte as such. Carbon dioxide, CO 2, is nonpolar, but can dissolve in water to produce carbonic acid, H 2 CO 3, which in turn contributes the H + and CO 3 2- ions; although by themselves they are not good conductors of electricity, since H 2 CO 3 is a weak electrolyte.
Solvents
Solvents, such as water, ethanol, methanol, chloroform, carbon tetrachloride, acetonitrile, and others, are non-electrolytes, because of them the amount of ions that are generated by their dissociation equilibria is negligible. Water, for example, produces negligible amounts of H 3 O + and OH - ions.
Now if these solvents can accommodate ions, then they will turn into electrolytic solutions. Such is the case with seawater and aqueous solutions saturated with salts.
Organic solids
Leaving out exceptions such as organic salts, most solids, mainly organic ones, are non-electrolytes. This is where sugar comes in again and the whole wide family of carbohydrates.
Among the non-electrolyte solids we can mention the following:
-The fats
-High molecular mass alkanes
-Rubbers
-Polystyrene foam
-Phenolic resins
-Plastics in general
-Anthracene
-Caffeine
-Cellulose
-Benzophenone
-Honey crystals
-Asphalt
-Urea
Final comment
As a final comment, a final summary of the general characteristics of a non-electrolyte will be made: they are covalent compounds, predominantly nonpolar, although with several polar exceptions, such as sugar and ice; They can be gaseous, liquid or solid, as long as they do not have ions or generate them when dissolved in an appropriate solvent.
References
- Whitten, Davis, Peck & Stanley. (2008). Chemistry (8th ed.). CENGAGE Learning.
- Toppr. (sf). Electrolytes and Non-electrolytes. Recovered from: toppr.com
- Helmenstine, Anne Marie, Ph.D. (February 11, 2020). Nonelectrolyte Definition in Chemistry. Recovered from: thoughtco.com
- The Sevier BV (2020). Nonelectrolytes. ScienceDirect. Recovered from: sciencedirect.com
- Dummies. (2020). How to Distinguish Electrolytes from Nonelectrolytes. Recovered from: dummies.com