The formula of salt is cookery. The chemical formula: table salt. Properties of table salt

The table salt is sodium chloride, used as a food additive, food preservative. It is also used in the chemical industry, medicine. Serves as the most important raw material for the production of caustic soda, hydrochloric acid, soda and other substances. The formula of salt is NaCl.

The formation of an ionic bond between sodium and chlorine

The chemical composition of sodium chloride reflects the conventional formula of NaCl, which gives an idea of an equal number of sodium and chlorine atoms. But matter is not formed by diatomic molecules, but consists of crystals. When an alkali metal interacts with a strong nonmetal, each sodium atom gives a valence electron to an electronegative chlorine. There are sodium cations Na ⁺ and anions of acidic residue of hydrochloric acid Cl ^- . The charged particles of different charge are attracted to form a substance with an ionic crystal lattice. Small sodium cations are located between large chlorine anions. The number of positive particles in the composition of sodium chloride is equal to the number of negative particles, the substance as a whole is neutral.

Chemical formula. Table salt and halite

Salts are complex substances of the ionic structure, the names of which begin with the name of the acid residue. The formula of salt is NaCl. Geologists mineral of such composition are called "halite", and sedimentary rock - "rock salt". An obsolete chemical term, which is often used in production, is "sodium chloride". This substance is known to people since ancient times, once it was considered "white gold." Modern students of schools and students when reading reaction equations involving sodium chloride are called chemical signs ("sodium chlorine").

We will carry out simple calculations using the formula of matter:

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 measurement g / mol: M (NaCl) = 58.44 g / mol.

3) A sample of 100 g salt contains 60.663 g of chlorine atoms and 39.337 g of sodium.

Physical properties of table salt

Fragile crystals of halite are colorless or white. In nature, there are also deposits of rock salt, painted in gray, yellow or blue. Sometimes a 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 dash on its surface.

Other physical parameters of sodium chloride:

• Odor - absent;
• Taste - salty;
• Density - 2,165 g / cm3 (20 ° C);
• Melting point - 801 ° C;
• Boiling point - 1413 ° C;
• Solubility in water - 359 g / l (25 ° C);

Preparation of sodium chloride in the laboratory

In the interaction of metallic sodium with gaseous chlorine, a white substance is formed in the test tube - sodium chloride NaCl (formula of table salt).

Chemistry gives an idea of the different ways of obtaining the same compound. Here are some examples:

Neutralization reaction: NaOH (aq.) + HCl = NaCl + H ₂ O.

Oxidation-reduction reaction between metal and acid:

2Na + 2HCl = 2NaCl + H ₂ .

The effect of the acid on the metal oxide: Na ₂ O + 2HCl (aq) = 2NaCl + H ₂ O

The displacement of a weak acid from a solution of its salt is stronger:

Na ₂ CO ₃ + 2HCl (aq) = 2NaCl + H ₂ O + CO ₂ (gas).

For use on an industrial scale, all these methods are too expensive and complex.

Production of table salt

Even at the dawn of civilization people knew that after salting meat and fish last longer. Transparent, regular-shaped crystals of halite were used in some ancient countries instead of money and were worth their weight in gold. The search and development of deposits of halite allowed to meet the growing needs of the population and industry. The most important natural sources of table salt:

• The deposits of the mineral galite in different countries;
• Water of the seas, oceans and salt lakes;
• Interlayers and crusts of rock salt on the banks of salt water bodies;
• Crystals of halite on the walls of volcanic craters;
• Solonchaks.

In the industry, there are four main ways to produce table salt:

• Leaching of halite from the underground layer, evaporation of the resulting brine;
• Extraction in salt mines;
• Evaporation of sea water or brine of saline lakes (77% of the dry residue is sodium chloride);
• Use of a by-product of desalination of saline waters.

Chemical properties of sodium chloride

NaCl is an average salt formed by alkali and a soluble acid. Sodium chloride is a strong electrolyte. The attraction between ions is so great that only strongly polar solvents can destroy it. In water, the ionic crystal lattice of the substance disintegrates, cations and anions (Na ⁺ , Cl-) are released. Their presence is due to the electrical conductivity, which has a solution of common salt. The formula in this case is written in the same way as for a dry substance - NaCl. One of the qualitative reactions to sodium cation is the yellow color of the burner flame. To get the result of the experiment, you need to put a bit of hard salt on a clean wire loop and put it into the middle part of the flame. The properties of table salt are also associated with the feature of the anion, which consists in a qualitative reaction to the chloride ion. When interacting with silver nitrate, a white precipitate of silver chloride precipitates in the solution (photo). Hydrogen chloride is displaced from the salt by stronger acids than hydrochloric acid: 2NaCl + H ₂ SO ₄ = Na ₂ SO ₄ + 2HCl. Under normal conditions, sodium chloride does not undergo hydrolysis.

Spheres of application of rock salt

Sodium chloride reduces the melting point of ice, so in winter, a mixture of salt and sand is used on roads and sidewalks. It absorbs a large number of impurities, melting rivers and streams when melting. Road salt also accelerates the process of corrosion of car bodies, damages trees planted next to roads. In the chemical industry, sodium chloride is used as raw material to produce a large group of chemicals:

• of hydrochloric acid;
• Metallic sodium;
• Gaseous chlorine;
• Caustic soda and other compounds.

In addition, table salt is used in the production of soaps, dyes. As food antiseptic is used for canning, pickling mushrooms, fish and vegetables. To combat thyroid disorders in the population, the salt formula is enriched by the addition of safe iodine compounds, for example KIO ₃ , KI, NaI. Such supplements support the production of thyroid hormone, prevent the disease endemic goiter.

The value of sodium chloride for the human body

The formula of salt is cookery, its composition has acquired a vital importance for human health. Sodium ions are involved in the transmission of nerve impulses. Anions of chlorine are necessary for the production of hydrochloric acid in the stomach. But too much sodium chloride in food can lead to high blood pressure and an increased risk of heart and vascular disease. In medicine, with great blood loss, patients are injected with physiological saline solution. To make it in a liter of distilled water, dissolve 9 g of sodium chloride. The human body needs a continuous supply of this substance with food. Salt is excreted through the excretory and skin. The average content of sodium chloride in the human body is about 200 g. Europeans consume about 2-6 g of table salt per day, in hot countries this figure is higher due to higher perspiration.