Table s alt is sodium chloride used as a food additive, food preservative. It is also used in the chemical industry, medicine. It serves as the most important raw material for the production of caustic soda, hydrochloric acid, soda and other substances. S alt formula - NaCl.
Formation of an ionic bond between sodium and chlorine
The chemical composition of sodium chloride reflects the conditional formula NaCl, which gives an idea of the equal number of sodium and chlorine atoms. But the substance is formed not by diatomic molecules, but consists of crystals. When an alkali metal interacts with a strong nonmetal, each sodium atom donates a valence electron to the more electronegative chlorine. There are sodium cations Na+ and anions of the acid residue of hydrochloric acid Cl-. Oppositely charged particles are attracted, forming a substance with an ionic crystal lattice. Small sodium cations are located between large chloride anions. Number of positive particles inthe composition of sodium chloride is equal to the number of negative, the substance as a whole is neutral.
Chemical formula. Table s alt and halite
S alts are complex substances of ionic structure, the names of which begin with the name of the acid residue. The formula for table s alt is NaCl. Geologists call a mineral of this composition “halite”, and sedimentary rock is called “rock s alt”. An obsolete chemical term that is often used in industry is "sodium chloride". This substance has been known to people since ancient times, it was once considered "white gold". Modern schoolchildren and students, when reading the equations of reactions involving sodium chloride, call chemical signs ("sodium chloride").
Let's carry out simple calculations using the formula of the substance:
1) Mr (NaCl)=Ar (Na) + Ar (Cl)=22.99 + 35.45=58.44.
The relative molecular weight is 58.44 (in amu).
2) The molar mass is numerically equal to the molecular weight, but this value has units of g/mol: M (NaCl)=58.44 g/mol.
3) A 100 g sample of s alt contains 60.663 g of chlorine atoms and 39.337 g of sodium atoms.
Physical properties of table s alt
Brittle crystals of halite - colorless or white. In nature, there are also deposits of rock s alt, painted in gray, yellow or blue. Sometimes the mineral substance has a red tint, which is due to the types and amount of impurities. The hardness of halite on the Mohs scale is only 2-2.5, the glass leaves a line on its surface.
Other physical parameters of sodium chloride:
- smell - absent;
- taste - s alty;
- density - 2, 165 g/cm3 (20 °C);
- melting point - 801 °C;
- boiling point - 1413 °C;
- solubility in water - 359 g/l (25 °C);
Obtaining sodium chloride in the laboratory
When metallic sodium reacts with gaseous chlorine in a test tube, a white substance is formed - sodium chloride NaCl (common s alt formula).
Chemistry gives an idea of different ways to get the same compound. Here are some examples:
Neutralization reaction: NaOH (aq.) + HCl=NaCl + H2O.
Redox reaction between metal and acid:
2Na + 2HCl=2NaCl + H2.
Acid action on metal oxide: Na2O + 2HCl (aq.)=2NaCl + H2O
Displacement of a weak acid from a solution of its s alt by a stronger one:
Na2CO3 + 2HCl (aq.)=2NaCl + H2 O + CO2 (gas).
For industrial use, all these methods are too expensive and complicated.
Production of common s alt
Even at the dawn of civilization, people knew that after s alting, meat and fish last longer. Transparent, regular-shaped halite crystals were used in some ancient countries instead of money and were worth their weight in gold. Search and development of halite depositsallowed to meet the growing needs of the population and industry. The most important natural sources of table s alt:
- deposits of the mineral halite in different countries;
- water of the seas, oceans and s alt lakes;
- layers and crusts of rock s alt on the banks of s alty reservoirs;
- halite crystals on the walls of volcanic craters;
- s alt marshes.
Industry uses four main ways to produce table s alt:
- leaching of halite from the underground layer, evaporation of the resulting brine;
- s alt mines;
- evaporation of sea water or brine from s alt lakes (77% of the mass of the dry residue is sodium chloride);
- using a by-product of desalination.
Chemical properties of sodium chloride
In its composition, NaCl is an average s alt formed by an alkali and a soluble acid. Sodium chloride is a strong electrolyte. The attraction between ions is so strong that only highly polar solvents can destroy it. In water, the ionic crystal lattice of a substance disintegrates, cations and anions are released (Na+, Cl-). Their presence is due to the electrical conductivity, which has a solution of common s alt. The formula in this case is written in the same way as for dry matter - NaCl. One of the qualitative reactions to the sodium cation is the yellow coloring of the burner flame. For experience resultsyou need to dial a little hard s alt on a clean wire loop and add it to the middle part of the flame. The properties of table s alt are also associated with the feature of the anion, which consists in a qualitative reaction to the chloride ion. When interacting with silver nitrate in solution, a white precipitate of silver chloride precipitates (photo). Hydrogen chloride is displaced from the s alt by stronger acids than hydrochloric: 2NaCl + H2SO4=Na2 SO4 + 2HCl. Under normal conditions, sodium chloride does not undergo hydrolysis.
Fields of application of rock s alt
Sodium chloride lowers the melting point of ice, so a mixture of s alt and sand is used on roads and sidewalks in winter. It absorbs a large amount of impurities, while thawing pollutes rivers and streams. Road s alt also accelerates the corrosion process of car bodies and damages trees planted next to roads. In the chemical industry, sodium chloride is used as a raw material for a large group of chemicals:
- hydrochloric acid;
- metal sodium;
- chlorine gas;
- caustic soda and other compounds.
In addition, table s alt is used in the production of soaps and dyes. As a food antiseptic, it is used in canning, pickling mushrooms, fish and vegetables. To combat thyroid disorders in the population, the table s alt formula is enriched by adding safe iodine compounds, for example, KIO3, KI, NaI. Such supplements support the production of thyroid hormone, prevent diseaseendemic goiter.
The importance of sodium chloride for the human body
The formula of table s alt, its composition has become vital for human he alth. Sodium ions are involved in the transmission of nerve impulses. Chlorine anions are necessary for the production of hydrochloric acid in the stomach. But too much s alt in food can lead to high blood pressure and increase the risk of developing heart and vascular diseases. In medicine, with a large blood loss, patients are injected with physiological saline. To obtain it, 9 g of sodium chloride is dissolved in one liter of distilled water. The human body needs a continuous supply of this substance with food. S alt is excreted through the excretory organs and skin. The average content of sodium chloride in the human body is approximately 200 g. Europeans consume about 2-6 g of table s alt per day, in hot countries this figure is higher due to higher sweating.
