Salts - substances belonging to the class of inorganic compounds, which consist of anion (acid residue) and cation (metal atom). In most cases, these are crystalline substances of various colors and with different solubilities in water. The simplest representative of this class of compounds is sodium chloride (NaCl).
Salts are divided into acidic, normal and basic.
Normal (average) forms when all the hydrogen atoms in the acid are replaced by metal atoms or when all the hydroxyl groups of the base are replaced by acidic acid residues (for example, MgSO4, Mg (CH3COO) 2). During electrolytic dissociation, they decompose into positively charged metal anions and negatively charged acid residues.
Chemical properties of salts of this group:
• decompose when exposed to high temperatures;
• undergo hydrolysis (interaction with water);
• enter into metabolic reactions with acids, other salts and bases. At the same time, some features of these reactions should be remembered:
- a reaction with an acid takes place only when this acid is stronger than the one from which the salt comes;
- a reaction with a base takes place when an insoluble substance is formed;
- the salt solution reacts with the metal if it is in the electrochemical series of voltages to the left of the metal, which is part of the salt;
- salt compounds in solutions interact with each other if an insoluble metabolic product is formed;
• redox, which can be associated with the properties of a cation or anion.
Acid salts are obtained in cases where only part of the hydrogen atoms in the acid are replaced by metal atoms (for example, NaHSO4, CaHPO4). During electrolytic dissociation, they form hydrogen and metal cations, anions of the acid residue, therefore, the chemical properties of the salts of this group include the following features of both salt and acid compounds:
• are thermally decomposed to form a medium salt;
• interact with alkali to form a normal salt.
Basic salts are obtained in cases where only part of the hydroxyl groups of the bases is replaced by acidic acid residues (for example, Cu (OH) or Cl, Fe (OH) CO3). Such compounds dissociate into metal cations and anions of hydroxyl and acid residue. The chemical properties of salts of this group include the characteristic chemical characteristics of both salt substances and bases simultaneously:
• thermal decomposition is characteristic;
• interact with acid.
There is also the concept of complex and double salts.
Complex contain a complex anion or cation. The chemical properties of salts of this type include decomposition reactions of complexes, accompanied by the formation of sparingly soluble compounds. In addition, they are able to exchange ligands between the internal and external spheres.
Double ones have two different cations and can react with alkali solutions (reduction reaction).
Methods for the preparation of salts
These substances can be obtained in the following ways:
• the interaction of acids with metals that can displace hydrogen atoms;
• during the reaction of bases and acids, when the hydroxyl groups of the bases exchange with acidic acid residues;
• the effect of acids on amphoteric and basic oxides, salts or metals;
• the action of bases on acid oxides;
• reaction between acidic and basic oxides;
• interaction of salts with each other or with metals (substitution reaction) ;
• salt production in reactions of metals with non-metals;
• acidic salt compounds are obtained by the reaction of a medium salt with the acid of the same name;
• basic salt substances are obtained by reacting salts with a small amount of alkali.
So, salts can be obtained in many ways, since they are formed as a result of many chemical reactions between various inorganic substances and compounds.