Salts are chemical compounds in which a metal atom is bonded to an acidic moiety. The difference between salts and other compounds is that they have a clearly expressed ionic bond. That is why the bond is called ionic. Ionic bonding is characterized by unsaturation and non-directionality. Examples of salts: sodium chloride or kitchen salt - NaCl, calcium sulfate or gypsum - CaSO4. Depending on how completely the hydrogen atoms in the acid or the hydroxo groups in the hydroxide are replaced, medium, acidic and basic salts are distinguished. A salt may contain several metal cations - these are double salts.

Medium salts

Medium salts are salts in which hydrogen atoms are completely replaced by metal ions. Kitchen salt and gypsum are such salts. Medium salts cover a large number of compounds often found in nature, for example, blende - ZnS, pyrrite - FeS2, etc. This type of salt is the most common.

Medium salts are obtained by a neutralization reaction when the base is taken in equimolar ratios, for example:
H2SO3 + 2 NaOH = Na2SO3 + 2 H2O
The result is medium salt. If you take 1 mole of sodium hydroxide, the reaction will proceed as follows:
H2SO3 + NaOH = NaHSO3 + H2O
The result is the acidic salt sodium hydrosulfite.

Acid salts

Acid salts are salts in which not all hydrogen atoms are replaced by a metal. Such salts are capable of forming only polybasic acids - sulfuric, phosphoric, sulfurous and others. Monobasic acids, such as hydrochloric, nitric and others, do not give.
Examples of acidic salts: sodium bicarbonate or baking soda - NaHCO3, sodium dihydrogen phosphate - NaH2PO4.

Acid salts can also be obtained by reacting medium salts with an acid:
Na2SO3+ H2SO3 = 2NaHSO3

Basic salts

Basic salts are salts in which not all hydroxo groups are replaced by acidic residues. For example, aluminum hydroxysulfate - Al(OH)SO4, zinc hydroxychloride - Zn(OH)Cl, copper dihydroxocarbonate or malachite -Cu2(CO3)(OH)2.

Double salts

Double salts are salts in which two metals replace hydrogen atoms in the acid moiety. Such salts are possible for polybasic acids. Examples of salts: potassium sodium carbonate - NaKCO3, potassium aluminum sulfate - KAl(SO4)2.. The most common double salts in everyday life are alum, for example, potassium alum - KAl(SO4)2 12H2O. They are used for water purification, tanning leather, and for loosening dough.

Mixed salts

Mixed salts are salts in which a metal atom is bonded to two different acidic residues, for example, bleach - Ca(OCl)Cl.

The science of chemistry brings the most valuable knowledge about substances, compounds, elements that surround a person and are part of his body. It is chemistry that studies acids and salts, their resistance to environments, formation, etc.

Acids and salts are complex substances of different origins.

Salts

Salts - which are formed during the reaction of an acid with a base, during which water is inevitably released.

Most known salts are formed by the interaction of substances with opposite properties. This reaction involves:
- metal,
- metal,
- basic oxide and acidic,
- base and acid,
- other elements.

The reaction of a salt and an acid also produces a salt. There are other salts, which boils down to indicating the complexity of the substance and its dissociation into cations and anions of acidic residues.

Salts are divided into three main types: acidic, moderate and basic. Acidic salts arise when there is an excess of acid; they only slightly replace hydrogen cations in acids with. Basic salts are the product of partial replacement of a base with acidic residues. But medium salts replace all the positive charges of hydrogen in acidic molecules with charges, or, as they correctly say, metal cations.

Salts that have the prefix “hydro-” in their name are acidic; the digital indicator reflects the number of hydrogen atoms. The name of the main salts includes the prefix “hydroxo-”. Some classes of salts have their own name, for example, alum.

Acids

Acids are complex substances that consist of hydrogen atoms and an acid residue. All acids are electrolytes.

Acids are classified according to three main characteristics: solubility, the presence of oxygen in the acid residue and the number of hydrogen atoms. Accordingly, according to solubility, acids are divided into soluble, insoluble and other reactions. The number of hydrogen atoms can fluctuate, depending on which acids can be monobasic, dibasic, or tribasic.

With the presence of oxygen, everything is simple: the acid residue is either oxygenic or oxygen-free.

At their core, acids contain either one or more hydrogen atoms and an acid residue. Due to the characteristic properties of acids, they have become widely used in medicine, industry and everyday life. There are a great variety of acidic substances: citric, boric, lactic and salicylic acids are most commonly used in everyday life.

For example, boric acid, which belongs to the class of weak acids, has a powder form with a crystalline structure. It dissolves best in hot water or special salt solutions. In the natural environment, boric acid can be found in mineral waters or hot springs.

Video on the topic

Sodium chloride, sodium chloride, sodium salt of hydrochloric acid are all different names for the same chemical substance - NaCl, which is the main component of table salt.

Instructions

Sodium chloride in its pure form is colorless crystals, but in the presence of impurities it can take on a yellow, pink, purple, blue or gray tint. NaCl occurs naturally in the form of the mineral halite, from which household salt is made. A huge amount of sodium chloride is also dissolved in sea water.

Halite is a transparent, colorless mineral with a glassy luster, having a face-centered cubic lattice (fcc lattice). It contains 60.66% chlorine and 39.34% sodium.

As can be seen from the definition, salts are similar in composition to acids, only instead of hydrogen atoms they contain metal ions. Therefore, they can also be called products of the replacement of hydrogen atoms in an acid with metal ions. For example, the well-known table salt NaCl can be considered as a product of the replacement of hydrogen in hydrochloric acid HCl with a sodium ion.

The charge of the sodium ion is 1+, and the charge of the chlorine ion is 1-. Since the compound is electrically neutral, the formula for table salt is Na + Cl - . If you need to derive the formula of aluminum (III) sulfide, proceed as follows.

1. Indicate the charges of the ions that make up the compound: Al 3+ S 2- . The charge of the aluminum ion is 3+, and the charge of the sulfur ion can be determined by the formula of the corresponding hydrosulfide acid H 2 S, it is equal to 2-.
2. Find the smallest common multiple of the numerical values ​​of the charges of aluminum and sulfur ions (3 and 2), it is equal to 6.
3. Find the indices by dividing the least common multiple by the magnitude of the charges and write the formula:

Formulas for salts of oxygen-containing acids having complex ions are derived similarly. Let us derive, for example, the formula for the calcium salt of phosphoric acid - calcium phosphate. Using the periodic table, we determine the charge of the calcium ion as an element of the main subgroup of group II (group IIA): 2+. Using the formula for phosphoric acid H 3 PO 4, we determine the charge of the ion formed by the acid residue: . Hence the formula for calcium phosphate is

(read “calcium three, pe-o-four twice”).

It is easy to see that when deriving formulas for salts based on the charges of ions, you must act in the same way as when deriving formulas for binary compounds based on valence and oxidation states of the elements that form them.

You have already looked at how the names of salts of oxygen-free acids are formed when you became familiar with the nomenclature of binary compounds: HCl salts are called chlorides, and H2S salts are called sulfides.

The names of salts of oxygen-containing acids are made up of two words: the name of the ion formed by the acid residue in the nominative case and the name of the metal ion in the genitive case. The names of the ions of acidic residues are, in turn, made up of the roots of the names of the elements, with the suffixes -am for the highest oxidation state and -it for the lowest oxidation state of the atoms of the non-metal element forming the complex ion of the oxygen-containing acid residue. For example, salts of nitric acid HNO 3 are called nitrates: KNO 3 - potassium nitrate, and salts of nitrous acid HNO 2 - nitrites: Ca(NO 2) 2 - calcium nitrite. If the metal exhibits different oxidation states, then they are indicated in brackets with Roman numerals, for example: Fe 2+ SO 3 - iron (II) sulfite and - iron (III) sulfate.

The nomenclature of salts is given in Table 5.

Table 5
Nomenclature of salts

Based on their solubility in water, salts are divided into soluble (P), insoluble (H) and slightly soluble (M). To determine the solubility of salts, use the table of solubility of acids, bases and salts in water. If you don’t have this table at hand, you can use the rules below. They are easy to remember.

1. All salts of nitric acid - nitrates - are soluble.
2. All salts of hydrochloric acid are soluble - chlorides, except AgCl (H), PbCl 2 (M).
3. All sulfuric acid salts are soluble - sulfates, except BaSO 4 (H), PbSO 4 (H), CaSO 4 (M), Ag 2 SO 4 (M).
4. Sodium and potassium salts are soluble.
5. All phosphates, carbonates, silicates and sulfides are insoluble, except these salts for Na+ and K+.

Let's consider the soluble sodium salt of oxygen-free hydrochloric acid - sodium chloride NaCl and insoluble calcium salts of carbonic and phosphoric acids - calcium carbonate CaCO 3 and calcium phosphate Ca 3 (PO 4) 2.

Laboratory experiment No. 12
Getting to know the salt collection

Check out the collection of salt samples given to you. Write down their formulas, characterize their physical properties, including solubility in water. Calculate the molecular (molar) masses of salts, as well as the mass fractions of the elements that form them. Find the mass of 2 moles of each salt.

Sodium chloride NaCl is a highly soluble salt in water, known as table salt. Without this salt, the life of plants, animals and humans is impossible, since it ensures the most important physiological processes in organisms: in the blood, salt creates the necessary conditions for the existence of red blood cells, in the muscles it determines the ability to excitability, in the stomach it forms hydrochloric acid, without which there would be impossible to digest and assimilate food. The need for salt for life has been known since ancient times. The meaning of salt is reflected in numerous proverbs, sayings, and customs. “Bread and salt” is one of the wishes that Russian people have long exchanged with each other during meals, emphasizing the equal value of salt with bread. Bread and salt became a symbol of hospitality and cordiality of the Russian nation.

They say: “To get to know a person, you have to eat a pound of salt with him.” It turns out that the wait is not so long: in two years, two people eat a pound of salt (16 kg), since each person consumes from 3 to 5.5 kg of salt in food per year.

The names of many cities and towns in different countries contain the word salt: Solikamsk, Sol-Iletsk, Usolye, Usolye-Sibirskoye, Salt Lake City, Saltville, Salzburg, etc.

Salt forms thick deposits in the earth's crust. In Sol-Iletsk, for example, the thickness of the salt layer exceeds one and a half kilometers. The salt found in Lake Baskunchak in the Astrakhan region will last our country for 400 years. The waters of the seas and oceans contain huge quantities of salt. Salt extracted from the World Ocean could cover the entire landmass of the globe with a layer of 130 m. In many countries of Asia and Africa, salt is extracted from salt lakes (Fig. 66, a), and in European countries - often from salt mines (Fig. 66, b).

Rice. 66.
Salt extraction:
a - from salt lakes; b - from the mines

Sodium chloride is widely used in the chemical industry to produce sodium, chlorine, hydrochloric acid, in medicine, for cooking, for food preservation (salting and fermenting vegetables), etc.

Calcium carbonate CaCO 3 is a water-insoluble salt from which numerous marine animals (molluscs, crayfish, protozoa) build the covers of their bodies - shells (Fig. 67) and corals.

Rice. 67.
These beautiful shells are made primarily of calcium carbonate

The remains of coral polyps, which you met in biology lessons, form tropical islands (atolls) and coral reefs (Fig. 68). The most famous is the Great Barrier Reef in Australia. Accumulating after the death of their “owners” at the bottom of reservoirs and mainly seas, these shells over tens and hundreds of millions of years formed powerful layers of calcium compounds, which gave rise to the formation of rocks - CaCO 3 limestones.

Rice. 68.
The most beautiful marine organisms - corals - build their skeleton from calcium carbonate. Their remains form coral atolls and reefs

The same formula has the same formula for building stone - marble, and chalk, so familiar to every schoolchild standing at the blackboard, which is mined from quarries or chalk mountains (Fig. 69). Quicklime and slaked lime are obtained from limestone and are used in construction. Marble is used to make statues, and metro stations are decorated with it.

Rice. 69.
Chalk Mountains

Land animals “build” their skeletons from calcium carbonate - internal support for soft tissues that are tens of times greater than the weight of the support itself.

Calcium phosphate Ca 3 (PO 4) 2, insoluble in water, is the basis of the minerals phosphorites and apatites. Phosphorus fertilizers are produced from them, without which it would be impossible to obtain high yields in agriculture. Calcium phosphate is also found in animal bones.

Key words and phrases

1. Salt.
2. Nomenclature of salts.
3. Drawing up formulas of salts.
4. Soluble, insoluble and slightly soluble salts.
5. Sodium chloride (table salt).
6. Calcium carbonate (chalk, marble, limestone).
7. Calcium phosphate.

Working with a computer

1. Refer to the electronic application. Study the lesson material and complete the assigned tasks.
2. Find email addresses on the Internet that can serve as additional sources that reveal the content of keywords and phrases in the paragraph. Offer your help to the teacher in preparing a new lesson - make a report on the key words and phrases of the next paragraph.

Questions and tasks

1. Make up formulas for sodium, calcium and aluminum salts for the following acids: nitric, sulfuric and phosphoric. Give them their names. Which salts are soluble in water?
2. Write down the formulas of the following salts: a) potassium carbonate, lead (II) sulfide, iron (III) nitrate; b) lead (IV) chloride, magnesium phosphate, aluminum nitrate.
3. From the listed formulas: H 2 S, K 2 SO 3, KOH, SO 3, Fe(OH) 3, FeO, N 2 O 3, Cu 3 (PO 4) 2, Cu 2 O, P 2 O 5, H 3 PO 4 - write down the formulas: a) oxides; b) acids; c) grounds; d) salts. Give the names of the substances.

Acid salts - This salt, which are formed by incomplete replacement of atoms hydrogen atoms in acid molecules metals.They contain two types of cations: a metal (or ammonium) cation and a hydrogen cation, and a multicharged anion acid residue. Cation hydrogen gives the name of the salt the prefix “hydro”, for example, sodium bicarbonate. Such salts dissociate in aqueous solutions into metal cations, hydrogen cations and anions of acid residues. They are formed when there is excess acids and contain hydrogen atoms. Acid salts are formed only by polybasic acids and exhibit the properties of both salts and acids. Acid salts of strong acids (hydrogen sulfates, dihydrogen phosphates) upon hydrolysis give an acidic reaction to the medium (which is what their name is associated with). At the same time, solutions of acid salts of weak acids (hydrocarbonates, tartrates) can have a neutral or alkaline reaction.

Physical properties

Acid salts - solid crystalline substances, having different solubility, and characterized by high melting points. The color of salts depends on the metal included in their composition.

Chemical properties

1. Acid salts react with metals located in the series of standard electrode potentials (Beketov series) to the left of the hydrogen atom:

2KНSO 4 + Mg = H 2 + MgSO 4 + K 2 SO 4,

2NaHCO 3 + Fe = H 2 + Na 2 CO 3 + Fe 2 (CO 3) 3

Since these reactions occur in aqueous solutions, metals such as lithium, sodium, potassium, barium and other active metals that react with water under normal conditions.

2. Acid salts react with acids if the resulting acid is weaker or more volatile than the reacting acid:

NaHCO 3 + HCl = NaCl + H 2 O + CO 2

To carry out such reactions, they usually take dry salt and treat it with concentrated acid.

3. Acidic salts react with aqueous solutions of alkalis to form a medium salt and water:

1) Ba(HCO 3) 2 + Ba(OH) 2 = 2BaCO 3 + 2H 2 O

2) 2KHSO 4 + 2NaOH = 2H 2 O + K 2 SO 4 + Na 2 SO 4,

3) NaHCO 3 + NaOH = H 2 O + Na 2 CO 3

Such reactions are used to obtain intermediate salts. 4. Acid salts react with salt solutions if, as a result of the reaction, a precipitate forms, gas is released, or water is formed:

1) 2KHSO 4 + MgCO 3 = H 2 O + CO 2 + K 2 SO 4 + MgSO 4,

2) 2KHSO 4 + BaCl 2 = BaSO 4 + K 2 SO 4 + 2HCl.

3) 2NaHCO 3 + BaCl 2 = BaCO 3 + Na 2 CO 3 + 2HCl

These reactions are used, among other things, to obtain practically insoluble salts.

5. Some acid salts decompose when heated:

1) Ca(HCO 3) 2 = CaCO 3 + CO 2 + H 2 O

2) 2NaHCO 3 = CO 2 + H 2 O + Na 2 CO 3

6. Acidic salts react with basic ones oxides with the formation of water and medium salts:

1) 2KHSO 4 + MgO = H 2 O + MgSO 4 + K 2 SO 4,

2) 2NaHCO 3 + CuO = H 2 O + CuCO 3 + Na 2 CO 3

7. When hydrolysis acid salts decompose into metal cations and acidic anions: KHSO 4 → K + + HSO 4–

The resulting acidic anions, in turn, reversibly dissociate: HSO 4– → H + + SO 4 2–

Receipt

Acid salts are formed when an excess acid reacts with an alkali. Depending on the number of moles of acid (in this case - orthophosphoric) dihydrogen orthophosphates can be formed (1) and hydroorthophosphates (2) :

Ba(OH) 2 + 2H 3 PO 4 → Ba(H 2 PO 4) 2 + 2H 2 O

Ba(OH) 2 + H 3 PO 4 → BaHPO 4 + 2H 2 O

When preparing acid salts, the molar ratios of the starting substances are important. For example, with a molar ratio of NaOH and H 2 SO 4 2:1, an average salt is formed:

2NaOH + H 2 SO 4 = Na 2 SO 4 + 2H 2 O And at a ratio of 1:1 - acidic: NaOH + H 2 SO 4 = NaHSO 4 + H 2 O

1. Acid salts are formed as a result of the interaction of acid solutions with metals that are in the activity series of metals to the left of hydrogen:

Zn + 2H 2 SO 4 = H 2 + Zn(HSO 4) 2,

2. Acid salts are formed as a result of the interaction of acids with basic oxides:

1) CaO + H 3 PO 4 = CaHPO 4 + H 2 O,

2) CuO + 2H 2 SO 4 = Cu(HSO 4) 2 + H 2 O

3. Acid salts are formed as a result of the interaction of acids with bases (neutralization reaction):

1) NaOH + H 2 SO 4 = NaHSO 4 + H 2 O

2) H 2 SO 4 + KOH = KHSO 4 + H 2 O

3) Mg(OH) 2 + 2H 2 SO 4 = Mg(HSO 4) 2 + 2H 2 O

Depending on the ratios of the concentrations of acids and bases involved in neutralization reactions, medium, acidic and basic salts can be obtained.

4. Acid salts can be obtained as a result of the interaction of acids and medium salts:

Ca 3 (PO 4) 2 + H 3 PO 4 = 3CaHPO 4

5. Acid salts are formed as a result of the interaction of bases with an excess of acidic oxide.

Salt comes in different tastes, sizes, shapes, colors and degrees of salinity. It all really depends on where she comes from. It is impossible to cover all the many types of salt, but the editor of the “Food” section of The Village, Anna Maslovskaya, decided to look into the issue and classify the main ones.

Origin

Sea salt is extracted from sun-concentrated brine that forms in areas where salt water floods. It is scraped off, dried, and sometimes recrystallized. Another way to obtain sea salt is by freezing. Not evaporation of water, but placing sea water in the cold.

Sad salt is obtained in a similar way to sea salt: by evaporating water from underground salt springs or by evaporating water in salt marshes. In these places, salt water stagnates on the surface of the earth, but does not come from the sea, but from other sources.

Rock salt, also known as mineral salt, is mined in mines. It is formed due to the flow of saline sources or, for example, in the place of dried up seas. Until recently, along with boiled sea salt, mineral salt was the most popular in the world.

Salt, depending on the method of its extraction, is then either ground or sifted. Thus, they divide it by caliber: from small to large.

Fine table salt

It's table salt. As a rule, it is of stone or cage origin. The second option is considered the cleanest. It is obtained by repeated recrystallization of brine and, apart from salt, contains little in itself - white table salt has a purity of at least 97%. While stone can contain a significant amount of impurities that affect the taste. When sifting it, you can find microscopic pieces of clay and stones. In Russia, the largest places for producing table salt are Lake Baskunchak in the Astrakhan region and Lake Elton in the Volgograd region.

Table salt has the purest salty taste, this is both its advantage and disadvantage. The main advantage is that it allows you to accurately dose the amount during preparation. The downside is that its taste is flat and one-dimensional. Table salt is one of the cheapest types of salt, along with mineral salt.

Kosher salt

A special case of ordinary table salt. It differs in that the size of its granules is larger than that of ordinary salt, and the shape of the crystals is different. Not cubes, but granules, flat or pyramidal in shape, obtained through a special evaporation process. The shape makes it easier to feel the amount of salt with your fingers, which is why in America, where it is produced in large quantities, it has become an industry standard in professional kitchens. The taste is almost no different from ordinary table salt, but there is a nuance: it is never iodized.

Salt is called kosher because it is used for koshering meat, that is, rubbing the carcass to remove residual blood.

Rock salt

Iranian blue salt

Table edible rock salt, grind No. 1

This is a large family, most often the name of which refers to white table salt mined in a mine. For example, salt extracted from the Artyomovskoye deposit in Ukraine, the supply of which to Russia is now limited due to sanctions. As a rule, it is white, but sometimes has a slightly gray or yellowish tint. Salts with brighter impurities often acquire their own names. For example, black Himalayan salt, which will be discussed below. Rock salt is also used for technical purposes - for example, to salt a swimming pool or sprinkle a road.

Sea salt

Sea iodized salt from the Adriatic Sea

Hawaiian Sea Salt Black Lava

There are many types of it due to its origin. Since all seas have different chemical profiles, this is reflected in the taste and composition of the salt. Sometimes this salt is recrystallized to obtain pure table salt. Its value lies in the variety of tastes and the presence of additional impurities that enrich the taste.

Fleur de sel

Fleur de sel from Lake Reux

Swedish salt flakes

Flaked salt is highly valued by both chefs and ordinary consumers. Depending on its origin, it differs in shape, appearance, humidity and degree of salinity. Its traditional name is fleur de sel. As a rule, this is sea salt, the crystals of which grow on the edges of the salt baths, in the process of slow evaporation of water they become overgrown with beautiful growths, which, as a rule, are collected by hand at a certain stage of growth. That is, from the same source you can get both coarse salt and salt flakes.

Salt is mined in flake form in a variety of places around the world, but the three most famous deposits are salt from the French island of Reux, Maldon salt from southeast England, and salt mined from a large deposit in Portugal.

Maldon is a very famous fleur de sel salt, mined in the Maldon area of ​​Essex in south-east England since the late 19th century. It is correct to say “Maldon”, although “Maldon” has already taken root in Russia. Moldon salt is a separate type of salt, which differs from fleur de sel in that its crystals are larger, up to a centimeter. It is also slightly saltier than the classic fleur de sel. Being sea salt and having a shape in the form of flat crystals, it is delicate and creates a pleasant sensation, exploding on the tongue with salty sparkles. This makes Moldon salt a versatile finishing agent for dishes.

Black Himalayan salt

Pink Himalayan salt

Coarsely ground mineral salt, the color of which is due to the presence of impurities of potassium chloride and iron oxide. In total, salt contains about 5% of all kinds of impurities. It is used in hand mills to finish dishes, that is, not only for salting the dish, but also for decoration.

Pink Himalayan salt is mined in large blocks, which are then cut, in the Punjab region, mainly in the troughs of the Himalayas, in Pakistan and India. Salt blocks are even used for interior work.

Pink Hawaiian salt

Sedimentary sea salt that was first collected in Hawaii. Now its main production takes place in California. The bright pink-brown color of medium-sized salt crystals is given by clay inclusions. An expensive product with a slightly iron taste. According to some reports, it is considered especially useful. But what you can’t argue with is that it’s beautiful, which makes it ideal for serving dishes.

Interesting fact

In foreign literature, the term “pink salt” refers to a special product based on salt with the addition of sodium nitrite, used for the production of meat products.

Flavored salts

Black Thursday salt

There are many types of aromatic salts, and all of them are invented and made by man. Such salt can be of any origin, the main thing in it is the combination of two functions: salting a dish with its flavoring. To do this, additives are placed in the salt or the necessary manipulations are performed on the salt itself, for example, smoking. Additives can be anything: flowers, spices, herbs, berries and even wine.

Thursday salt stands apart on this list because it is the result of rather complex manipulations. Initially, this salt was ritual (like pink Hawaiian salt), but now it is more often used because of its unusual taste. This salt is prepared as follows: table salt is mixed in equal proportions with kvass grounds or rye bread soaked in water; they put it in the oven (sometimes burying it in ashes), oven, or heat it in a frying pan. Afterwards, the monolithic piece is split and pounded in a mortar.

Interesting fact

Charcoal salt is used in many culinary traditions, such as in Japan and Korea. Just like the Thursday one, it is made by human hands. A similar example from Korea is bamboo salt: mOrsk salt is literally baked in bamboo.

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

Formation of an ionic bond between sodium and chlorine

The chemical composition of sodium chloride is reflected by the conventional formula NaCl, which gives an idea of ​​the equal number of sodium and chlorine atoms. But the substance is not formed by diatomic molecules, but consists of crystals. When an alkali metal reacts with a strong nonmetal, each sodium atom gives up the more electronegative chlorine. Sodium cations Na + and anions of the acidic residue of hydrochloric acid Cl - appear. Oppositely charged particles attract each other, forming 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 ones; the substance as a whole is neutral.

Chemical formula. Table salt and halite

Salts are complex substances of ionic structure, the names of which begin with the name of the acidic residue. The formula for table salt is NaCl. Geologists call a mineral of this composition “halite,” and a sedimentary rock “rock salt.” An outdated chemical term that is often used in manufacturing 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 reaction equations involving sodium chloride, use chemical symbols (“sodium chlorine”).

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 value is 58.44 (in amu).

2) Molar mass is numerically equal to molecular weight, but this quantity has units of measurement g/mol: M (NaCl) = 58.44 g/mol.

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

Physical properties of table salt

Fragile halite crystals are colorless or white. In nature, there are also deposits of rock salt, colored grey, 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 is only 2-2.5, glass leaves a line on its surface.

Other physical parameters of sodium chloride:

• smell - 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

When metallic sodium reacts with chlorine gas in a test tube, a white substance is formed - sodium chloride NaCl (formula of table salt).

Chemistry provides insight into different ways of producing the same compound. Here are some examples:

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

Redox reaction between a metal and an acid:

2Na + 2HCl = 2NaCl + H2.

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

Displacement of a weak acid from a solution of its salt by a stronger one:

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

All these methods are too expensive and complex for use on an industrial scale.

Production of table salt

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

• deposits of the mineral halite in different countries;
• water of seas, oceans and salt lakes;
• layers and crusts of rock salt on the banks of salty reservoirs;
• halite crystals on the walls of volcanic craters;
• salt marshes.

The industry uses four main methods for producing table salt:

• leaching of halite from the underground layer, evaporation of the resulting brine;
• mining in ;
• evaporation or brine of salt lakes (77% of the mass of the dry residue is sodium chloride);
• using a by-product of salt water desalination.

Chemical properties of sodium chloride

In terms of its composition, NaCl is an average salt 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 break it. In water, the substance disintegrates, cations and anions (Na +, Cl -) are released. Their presence is due to the electrical conductivity possessed by a solution of table salt. 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 color of the burner flame. To obtain the result of the experiment, you need to collect a little solid salt on a clean wire loop and add it to the middle part of the flame. The properties of table salt are also associated with the peculiarity 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.

Areas of application of rock salt

Sodium chloride lowers the melting point of ice, so in winter a mixture of salt and sand is used on roads and sidewalks. It absorbs a large amount of impurities and, when melting, pollutes rivers and streams. Road salt 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 the production of a large group of chemicals:

• hydrochloric acid;
• sodium metal;
• chlorine gas;
• caustic soda and other compounds.

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

The importance of sodium chloride for the human body

The formula of table salt, its composition has acquired vital importance for human health. 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 salt in food can lead to high blood pressure and an increased risk of developing heart and vascular diseases. In medicine, when there is a large blood loss, patients are given physiological saline solution. To obtain it, 9 g of sodium chloride are dissolved in one liter of distilled water. The human body needs a continuous supply of this substance from food. Salt is excreted through the excretory organs and skin. The average sodium chloride content in the human body is approximately 200 g. Europeans consume about 2-6 g of table salt per day; in hot countries this figure is higher due to higher sweating.