Oxides, acids and salts, excluding the main classes of inorganic substances, refer to a group of compounds called bases or hydroxides. They all have the same scheme for the structure of the molecule: they basically contain one or more hydroxyl groups attached to a metal ion. Basic hydroxides are genetically related to metal oxides and salts, this accounts for not only their chemical properties, but also methods of production in the laboratory and industry.
There are several forms of classification bases, which are based on the characteristics of the metal that is part of the molecule, and on the ability of the substance to dissolve in water. In this article we will consider these features of hydroxides, and get acquainted with their chemical properties, on which the basis of bases in industry and everyday life depend.
physical properties
All bases formed by active or typical metals, are solids with a wide range of melting. With respect to water, they are divided into highly soluble – alkali and insoluble in water. For example, basic hydroxides containing elements of group Ia dissolve readily in water and are strong electrolytes. They’re called soap-to-touch, fabric, skin-coating, and alkali. When they dissociate in solution, OH ions are detected –Determined by means of indicators, for example, colorless phenolphthalein turns red in an alkaline medium. Both solutions and melts of sodium, potassium, barium, calcium hydroxides are electrolytes, ie. Conduct an electric current and are considered another type of conductor. The most commonly used for soluble bases in industry are, for example, about 11 compounds, such as the basic hydroxides of sodium, potassium, ammonium, etc.
structure of base molecule
Between the ions of the metal cation and the hydroxylgroups in the molecule of the substance, an ionic bond is formed. It is strong enough for water-insoluble hydroxides, so polar water molecules are not able to destroy the crystal lattice of such a complex. Alkali substances are substances that are stable and practically do not heat oxides and water. Therefore, the basic hydropower of potassium and sodium boil at a temperature of more than 1000 ° C, while they do not decompose. In the graphical formulas of all bases it is clearly seen that the oxygen atom of the hydroxyl group is bonded to one covalent bond of the metal atom and the other to the hydrogen atom. The structure of the molecule and the types of chemical bonds cause not only physical, but all chemical characteristics of substances. Let us look at them in more detail.
Properties of calcium and magnesium and their compounds
Both elements are typical representatives of active metals and can interact with oxygen and water. The product of the first reaction is the parent oxide; the hydroxide is produced as a result of an exothermic process, proceeding with the release of a large amount of heat. The bases of calcium and magnesium are small soluble white powdery substances. For the calcium complex, the following names are often used: milk of lime (if the suspension is in water) and lime water. Being a typical basic hydroxide, Ca (OH) 2 interacts with acidic and amphotic oxides, acids and amphoteric bases, for example, with aluminum and zinc hydroxides. Unlike typical alkalis, which are resistant to heat, magnesium and calcium compounds oxide and shrink into water under the influence of temperature. Both bases, especially Ca(OH) 2, are widely used in industry, agriculture and household needs. Let’s look at their application further.
Fields of application of calcium and magnesium compounds
It is well known that in the construction industry a chemical material called cannon or slaked lime is a base of calcium. Often it is obtained by reaction of water with basic calcium oxide. The chemical properties of basic hydroxides make it possible to widely use them in various branches of the national economy. For example, in bleaching cotton and linen yarn, to produce bleach, to clear defects in the production of raw sugar. Before the invention of ion exchangers – cation exchangers, calcium and magnesium bases employed water softening techniques that could get rid of hydrocarbons, deteriorating their quality. For this, water was boiled with a small amount of soda ash or hydrated lime. Aqueous solutions of magnesium hydroxide as a therapeutic agent for patients with gastritis can be used to reduce gastric acidity.
Properties of basic oxides and hydroxides
The most important groups of substances for reactions with acidic oxides, acids, amphoteric bases and salts. Interestingly, insoluble bases, for example, cannot be obtained by direct reaction of oxides with water such as copper, iron or nickel hydroxides. In this case, the reaction between the corresponding salt and base is used in the laboratory. As a result, bases are formed that precipitate. For example, in this way a blue precipitate of copper hydroxide is obtained, a green precipitate of a base of ferrous iron. Thereafter, they are dried to solid powder substances related to water-insoluble hydroxides. A distinctive feature of these compounds is that, under the action of high temperatures, they dissolve in the corresponding oxides and water, which cannot be said about alkalis. After all, water soluble bases are thermally stable
Electrolysis potential
Continuing to study the basic properties of hydroxides, focus is on one line, which can be distinguished from water-insoluble compounds on the basis of alkali and alkaline earth metals. It is the inability of the latter to dissociate into ions under the current work of electricity. In contrast, melts and solutions of hydroxides of potassium, sodium, barium, strontium and readily undergo electrolysis are other types of conductors.
make up chairs
Speaking about the properties of this class of inorganicsubstances, we have partially listed the chemical reactions that produce their production under laboratory and industrial conditions. The most affordable and economically profitable is the method of thermal decomposition of natural limestone, which occurs in the production of qualite. If reacted with water, it forms a basic hydroxide – Ca(OH) 2 . The mixture of this substance with sand and water is called mortar. It is being used for building walls, for crushing bricks and for other types of construction work. Alkali can also be obtained by reacting the corresponding oxide with water. For example: K 2 O + H 2 O = 2KOH The process is NE with the release of a large amount of heat
The interaction of bases with acidic and amphoteric oxides
Characteristics of soluble to chemical properties of water bases can be attributed to their ability to form salts in reactions with oxides containing non-metal atoms in molecules, for example, such as carbon dioxide, sulfur dioxide or silicon oxide. Specifically, calcium hydroxide is used to produce the gases, and sodium and potassium hydroxides to produce the corresponding carbonates. Zinc and aluminum oxides belonging to amphoteric substances can interact with both acids and alkalis. In the latter case, complex compounds can be formed, for example, such as sodium hydroxo-zinc.
Neutral reaction
One of the most important properties of bases such as water, and insoluble in alkalis, is their ability to react with inorganic or organic acids. This reaction is reduced to the interaction of two types of ions: hydrogen and hydroxyl groups. This leads to the formation of water molecules: about HCl + KOH = KCl + H 2 . From the point of view of the principle of electrolytic dissociation, the entire reaction is reduced to the formation of a weakly dissolved electrolyte – water.
In this example, the average salt formed was -potassium chloride. If, for the reaction, the basic hydroxide is taken in the amount necessary to completely neutralize the polybasic acid, then upon evaporation of the product formed, crystals of the acid salt are detected. The neutralization reaction plays an important role in metabolic processes occurring in living systems-cells and allows them, with their own buffer complexes, to neutralize excess amounts of hydrogen ions that accumulate in dissolution reactions.
