Many oxides of active metals, such as oxides of potassium, sodium or lithium, can interact with water. In this case, compounds related to hydroxides are found in the reaction products. The properties of these substances, the features of the course of chemical processes in which bases are involved, are due to the presence of a hydroxyl group in their molecules. So, in the reactions of electrolytic dissociation, bases are split into metal ions and anions OH-. How bases interact with non-metal oxides, acids and s alts, we will consider in our article.
Nomenclature and structure of the molecule
To correctly name the base, you need to add the word hydroxide to the name of the metal element. Let's give specific examples. The aluminum base belongs to amphoteric hydroxides, the properties of which we will consider in the article. The obligatory presence in base molecules of a hydroxyl group bound to a metal cation by an ionic bond type can be determined usingindicators such as phenolphthalein. In an aqueous medium, an excess of OH- ions is determined by a change in the color of the indicator solution: colorless phenolphthalein becomes crimson. If a metal exhibits multiple valences, it can form multiple bases. For example, iron has two bases, in which the metal valency is 2 or 3. The first compound is characterized by the features of basic hydroxides, the second is amphoteric. Therefore, the properties of higher hydroxides differ from compounds in which the metal has a lower degree of valence.
Physical characteristics
The bases are solids that are resistant to heat. In relation to water, they are divided into soluble (alkali) and insoluble. The first group is formed by chemically active metals - elements of the first and second groups. Substances insoluble in water are composed of atoms of other metals, whose activity is inferior to sodium, potassium or calcium. Examples of such compounds are iron or copper bases. The properties of hydroxides will depend on which group of substances they belong to. So, alkalis are thermally stable and do not decompose when heated, while water-insoluble bases are destroyed under the action of high temperature, forming an oxide and water. For example, a copper base decomposes as follows:
Cu(OH)2=CuO + H2O
Chemical properties of hydroxides
The interaction between the two most important groups of compounds -acids and bases are called neutralization reactions in chemistry. This name can be explained by the fact that chemically aggressive hydroxides and acids form neutral products - s alts and water. Being, in fact, an exchange process between two complex substances, neutralization is characteristic of both alkalis and water-insoluble bases. Here is the equation for the neutralization reaction between caustic potash and hydrochloric acid:
KOH + HCl=KCl + H2O
An important property of alkali metal bases is their ability to react with acidic oxides, resulting in s alt and water. For example, by passing carbon dioxide through sodium hydroxide, you can get its carbonate and water:
2NaOH + CO2=Na2CO3 + H 2O
Ion exchange reactions include the interaction between alkalis and s alts, which leads to the formation of insoluble hydroxides or s alts. So, pouring dropwise a solution of caustic soda into a solution of copper sulfate, you can get a blue jelly-like precipitate. It is a copper base, insoluble in water:
CuSO4 + 2NaOH=Cu(OH)2 + Na2 SO 4
The chemical properties of hydroxides, insoluble in water, differ from alkalis in that they lose water upon slight heating - they dehydrate, turning into the form of the corresponding basic oxide.
Grounds exhibiting dual properties
If an element or a complex substance can react with both acids and alkalis, it is called amphoteric. These include, for example, zinc,aluminum and their bases. The properties of amphoteric hydroxides make it possible to write their molecular formulas both in the form of bases, while isolating the hydroxo group, and in the form of acids. Let us present several equations for the reactions of an aluminum base with hydrochloric acid and sodium hydroxide. They illustrate the special properties of amphoteric hydroxides. The second reaction takes place with the decay of alkali:
2Al(OH)3 + 6HCl=2AlCl3 + 3H2O
Al(OH)3 + NaOH=NaAlO2 + 2H2O
The products of the processes will be water and s alts: aluminum chloride and sodium aluminate. All amphoteric bases are insoluble in water. They are mined as a result of the interaction of the corresponding s alts and alkalis.
Methods of obtaining and application
In the industry that requires large volumes of alkalis, they are obtained by electrolysis of s alts containing cations of active metals of the first and second groups of the periodic system. The raw material for the extraction, for example, caustic sodium, is a solution of common s alt. The reaction equation will be:
2NaCl + 2H2O=2NaOH + H2 + Cl2
The bases of low-active metals in the laboratory are obtained by the interaction of alkalis with their s alts. The reaction belongs to the type of ion exchange and ends with the precipitation of the base. A simple way to obtain alkalis is a substitution reaction between the active metal and water. It is accompanied by heating of the reacting mixture and is of the exothermic type.
Properties of hydroxides are used in industry. Alkalis play a special role here. They are used as purifiers for kerosene and gasoline, for making soap, processing natural leather, as well as in technologies for the production of rayon and paper.
