Chemical function is a grouping of substances that have similar properties. These properties are called functional, as they determine the behavior of substances.
The main inorganic chemical functions are: acids, bases, salts and oxides.
Acids
Acids are compounds formed by covalent bonds, where electrons are shared. According to chemist Svante Arrhenius (1859-1927) these compounds release H ions+ when they are in contact with water.
How to identify an acid?
The general formula for an acid is HxA, where A represents the anion, H is hydrogen and x is the number of atoms of this element present in the molecule.
Today, we know that in contact with water an acid releases the H as the only cation.+ and forms the hydronium ion on ionization. Furthermore, when acids are ionized in an aqueous solution, they are capable of conducting electricity.
The strength of an acid is measured by its ability to ionize in contact with water. The more acid molecules ionize in water, the stronger the acid.
Example: HCl is a strong acid, as it has a 92% ionization degree. the H
2CO3 it is a weak acid, as only 0.18% of acid molecules are ionized in solution.Classification of acids
We can classify acids according to the number of ionizable hydrogens in:
- Monoacid: has only one ionizable hydrogen, such as HCN;
- Diacid: has two ionizable hydrogens, like H2ONLY3;
- Triacid: has three ionizable hydrogens, such as H3DUST4;
- Tetracid: has four ionizable hydrogens, like H4P2O7.
Acids are also classified by the absence of oxygen in hydrates, such as HCl and HCN, and when there is the oxygen element, they are called oxyacids, like H2ONLY4 and HNO3.
Examples of acids
- sulfuric acid, H2ONLY4
- Hydrochloric acid, HCl
- Hydrofluoric acid, HF
- Nitric acid, HNO3
- Phosphoric Acid, H3DUST4
- Carbonic acid, H2CO3
Learn more about acids.
Bases
The bases are compounds formed by ionic bonds, where there is the donation of electrons. According to chemist Svante Arrhenius (1859-1927) these compounds release OH ions- when they are in contact with water, as the compound dissociates.
How to identify a base?
The general formula for a base is , where B represents the cation (positive radical) that makes up the base and y is the charge that determines the number of hydroxyls (OH-).
The bases have an astringent, caustic and bitter taste. When they dissociate in an aqueous medium, the bases also conduct electricity.
Bases are compounds that dissociate in aqueous solution and the strength of a base is measured by the degree of dissociation. Therefore, the more structures dissociate in water, the stronger the base.
Example: NaOH is a strong base, as it has a 95% ionization degree. NH4OH is a weak base as only 1.5% of the compound undergoes ionic dissociation.
Base classification
The bases can be classified according to the number of hydroxyls they release in solution in:
- Monobase: has only one hydroxyl, like NaOH;
- Dibase: has two hydroxyls, like Ca (OH)2;
- Tribase: has three hydroxyls, such as Al (OH)3;
- Tetrabase: has four hydroxyls, like Pb (OH)4.
The alkali metal and alkaline earth metal bases, with the exception of beryllium and magnesium, are considered strong bases due to their high degree of dissociation. Weak bases, on the other hand, have a degree of dissociation below 5%, such as NH4OH and Zn(OH)2.
Examples of bases
- Sodium hydroxide, NaOH
- Ammonium hydroxide, NH4oh
- Potassium hydroxide, KOH
- Magnesium hydroxide, Mg(OH)2
- Iron hydroxide, Fe(OH)3
- Calcium hydroxide, Ca(OH)2
Learn more about bases.
salts
Salts are compounds produced from the reaction that takes place between an acid and a base, called a neutralization reaction.
Therefore, a salt is formed by a cation that comes from a base and an anion that comes from the acid.
How to identify a salt?
Salts are ionic compounds whose structure is CxTHEy formed by a C cationy+ (positive ion), other than H+, and an anion Ax- (negative ion), which is different from OH-.
Salts in ambient conditions appear as crystalline solids, with a high melting and boiling point. In addition, many have a characteristic salty taste.
Although some salts are well known and used in food, such as sodium chloride (table salt) there are salts that are extremely toxic.
When in aqueous solution, salts are capable of conducting electricity. Many salts can easily absorb moisture from the environment and are therefore called hygroscopic.
Classification of salts
Salts are classified according to their character in aqueous solution.
neutral salt: formed by strong base cation and strong acid anion or weak base cation and weak acid anion.
Example: HCl (strong acid) + NaOH (strong base) → NaCl (neutral salt) + H2O (water)
acid salt: Formed by weak base cation and strong acid anion.
Example: HNO3 (strong acid) + AgOH (weak base) → AgNO3 (acid salt) + H2O (water)
basic salt: formed by strong base cation and weak acid anion.
Example: H2CO3 (weak acid) + NaOH (strong base) → NaHCO3 (basic salt) + H2O (water)
Examples of salts
- Potassium nitrate, KNO3
- Sodium hypochlorite, NaClO
- Sodium Fluoride, NaF
- Sodium carbonate, Na2CO3
- Calcium Sulfate, CaSO4
- Aluminum Phosphate, AlPO4
Learn more about salts.
Oxides
Oxides are compounds formed by two chemical elements, one of which is oxygen, which is the most electronegative of the compound.
How to identify an oxide?
The general formula for an oxide is , where C represents the cation (positive ion) bound to oxygen. The y (cation charge) indicates how many oxygen atoms must make up the oxide.
Oxides are binary substances, where oxygen is linked to a chemical element that is less electronegative than it. Therefore, the binding of oxygen to fluorine, as in OF compounds2 it's the2F2, are not considered oxides.
Classification of oxides
Molecular oxides (oxygen + ametal) have an acidic character, because when they are in aqueous solution they react producing acids, such as carbon dioxide (CO2).
Ionic oxides (oxygen + metal) have a basic character, as in contact with water they form basic solutions, such as calcium oxide (CaO).
When an oxide does not react with water, such as carbon monoxide (CO), it is characterized as a neutral oxide.
Examples of oxides
- Tin oxide, SnO2
- Iron oxide III, Fe2O3
- Sodium oxide, Na2O
- Lithium Oxide, Li2O
- Tin dioxide, SnO2
- Nitrogen dioxide, NO2
Learn more about oxides.
Attention!
The classes of acids, bases, salts and oxides are organized as chemical functions to facilitate the study of inorganic compounds, since the number of substances is very large.
However, they can sometimes mix, as in the case of salts and oxides, which can have an acidic or basic character. Furthermore, the behavior of substances is influenced by their interaction with other compounds.
In Organic Chemistry, it is possible to visualize the different functional groups of organic compounds.
Also know the organic functions.
Main inorganic compounds
Check out some examples of compounds from inorganic functions and what are its applications.
Acids
Hydrochloric acid, HCl
Hydrochloric acid is a strong monoacid. It is an aqueous solution that contains 37% HCl, hydrogen chloride, a colorless, very toxic and corrosive gas.
It is used for cleaning metals, in the leather manufacturing process and as a raw material for other chemical compounds. This substance is marketed as muriatic acid for cleaning floors, tiles and metal surfaces.
sulfuric acid, H2ONLY4
O sulfuric acid it's a strong diacid. It is a colorless and viscous liquid, which is considered strong because its degree of ionization is greater than 50% at a temperature of 18º C.
This inorganic acid is used on a large scale in the chemical industry, as a raw material for the manufacture of many materials and, therefore, their consumption can indicate the economic development index of a country.
Bases
Magnesium hydroxide, Mg(OH)2
Magnesium hydroxide is a dibase, as it has two hydroxyls in its constitution. Under ambient conditions, the chemical compound is a white solid and its suspension in water is marketed under the name Milk of Magnesia.
Milk of magnesia is used as an antacid, to reduce stomach acid, and as a laxative, improving intestinal functions.
Sodium hydroxide, NaOH
O sodium hydroxide, also called caustic soda, in ambient conditions is in a solid state, has an off-white color and is highly toxic and corrosive.
It is a strong base, used both in industry, for the manufacture of cleaning products, and in domestic use, to unclog pipes, for example.
The use of the product requires a lot of care, as contact with the skin can cause severe burns.
salts
Sodium chloride, NaCl
Table salt, whose chemical name is sodium chloride, is a substance widely used as a seasoning and food preservative.
One of the techniques used to produce table salt is to evaporate sea water and crystallize the chemical compound. Subsequently, the salt undergoes a refinement process.
Another way in which sodium chloride is present in our lives is in saline, an aqueous solution with 0.9% of the salt.
Sodium Bicarbonate, NaHCO3
Sodium hydrogen carbonate, popularly known as sodium bicarbonate, is a salt with very small, powdery crystals that easily dissolves in water.
It is a substance with many domestic applications, whether for cleaning, mixed with other compounds, or for health, as it is present in the composition of effervescents.
Oxides
hydrogen peroxide, H2O2
O hydrogen peroxide it is marketed as a solution called hydrogen peroxide, a highly oxidizing liquid. When not dissolved in water, hydrogen peroxide is quite unstable and breaks down quickly.
The main applications of the hydrogen peroxide solution are: antiseptic, whitening and hair bleach.
carbon dioxide, CO2
O carbon dioxide, also called carbon dioxide, is a colorless, odorless, and heavier-than-air molecular oxide.
In photosynthesis the CO2 Atmospheric is captured from the atmosphere and reacts with water, producing glucose and oxygen. Therefore, this process is important for the renewal of oxygen in the air.
However, the high concentration of carbon dioxide in the atmosphere is one of the causes for the aggravation of the greenhouse effect, retaining a greater amount of heat in the atmosphere.
