What group is chlorine in? Physical properties of chlorine: density, heat capacity, thermal conductivity of Cl2

Ion radius (+7e)27 (-1e)181 pm Electronegativity
(according to Pauling) 3.16 Electrode potential 0 Oxidation states 7, 6, 5, 4, 3, 1, −1 Thermodynamic properties of a simple substance Density (at -33.6 °C)1.56
/cm³ Molar heat capacity 21.838 J /( mol) Thermal conductivity 0.009 W /( ) Melting temperature 172.2 Melting heat 6.41 kJ / mol Boiling temperature 238.6 Heat of evaporation 20.41 kJ/mol Molar volume 18.7 cm³/mol The crystal lattice of a simple substance Lattice structure orthorhombic Lattice parameters a=6.29 b=4.50 c=8.21 c/a ratio — Debye temperature n/a K

Chlorine (χλωρός - green) - element main subgroup the seventh group, the third period of the periodic system of chemical elements of D. I. Mendeleev, with atomic number 17. It is denoted by the symbol Cl (lat. Chlorum). Reactive nonmetal. It belongs to the group of halogens (originally, the name "halogen" was used by the German chemist Schweiger for chlorine [literally, "halogen" is translated as salt), but it did not take root, and subsequently became common for the VII group of elements, which includes chlorine).

The simple substance chlorine (CAS number: 7782-50-5) under normal conditions is a yellowish-green poisonous gas with a pungent odor. The chlorine molecule is diatomic (formula Cl2).

Chlorine atom diagram

Chlorine was first obtained in 1772 by Scheele, who described its release during the interaction of pyrolusite with hydrochloric acid in his treatise on pyrolusite:

4HCl + MnO 2 \u003d Cl 2 + MnCl 2 + 2H 2 O

Scheele noted the smell of chlorine, similar to the smell of aqua regia, its ability to interact with gold and cinnabar, as well as its bleaching properties.

However, Scheele, in accordance with the phlogiston theory prevailing in chemistry at that time, suggested that chlorine is dephlogisticated hydrochloric acid, that is, hydrochloric acid oxide. Berthollet and Lavoisier suggested that chlorine is an oxide of the element murium, but attempts to isolate it remained unsuccessful until the work of Davy, who managed to decompose table salt into sodium and chlorine by electrolysis.

Distribution in nature

In nature, there are two isotopes of chlorine 35 Cl and 37 Cl. Chlorine is the most abundant halogen in the earth's crust. Chlorine is very active - it combines directly with almost all elements of the periodic table. Therefore, in nature, it occurs only in the form of compounds in the composition of minerals: halite NaCl, sylvin KCl, sylvinite KCl NaCl, bischofite MgCl 2 6H2O, carnallite KCl MgCl 2 6H 2 O, kainite KCl MgSO 4 3H 2 O. The largest reserves of chlorine are contained in the salts of the waters of the seas and oceans.

The share of chlorine accounts for 0.025% of total number atoms of the earth's crust, the Clarke number of chlorine is 0.19%, and the human body contains 0.25% chlorine ions by mass. In humans and animals, chlorine is found mainly in intercellular fluids (including blood) and plays an important role in the regulation of osmotic processes, as well as in processes associated with the functioning of nerve cells.

Isotopic composition

In nature, there are 2 stable isotopes of chlorine: with a mass number of 35 and 37. The proportions of their content are respectively 75.78% and 24.22%.

Isotope	Relative mass, a.m.u.	Half life	Decay type	nuclear spin
35Cl	34.968852721	stable	—	3/2
36Cl	35.9683069	301000 years	β-decay in 36 Ar	0
37Cl	36.96590262	stable	—	3/2
38Cl	37.9680106	37.2 minutes	β-decay in 38 Ar	2
39Cl	38.968009	55.6 minutes	β-decay in 39 Ar	3/2
40Cl	39.97042	1.38 minutes	β-decay in 40 Ar	2
41Cl	40.9707	34 c	β-decay in 41 Ar
42Cl	41.9732	46.8 s	β-decay in 42 Ar
43Cl	42.9742	3.3 s	β-decay in 43 Ar

Physical and physico-chemical properties

Under normal conditions, chlorine is a yellow-green gas with a suffocating odor. Some of its physical properties are presented in the table.

Some physical properties of chlorine

Property	Meaning
Boiling temperature	-34°C
Melting temperature	-101°C
Decomposition temperature (dissociations into atoms)	~1400°С
Density (gas, n.o.s.)	3.214 g/l
Affinity for the electron of an atom	3.65 eV
First ionization energy	12.97 eV
Heat capacity (298 K, gas)	34.94 (J/mol K)
Critical temperature	144°C
critical pressure	76 atm
Standard enthalpy of formation (298 K, gas)	0 (kJ/mol)
Standard entropy of formation (298 K, gas)	222.9 (J/mol K)
Enthalpy of fusion	6.406 (kJ/mol)
Boiling enthalpy	20.41 (kJ/mol)

When cooled, chlorine turns into a liquid at a temperature of about 239 K, and then below 113 K it crystallizes into an orthorhombic lattice with a space group cmca and parameters a=6.29 b=4.50 , c=8.21 . Below 100 K, the orthorhombic modification of crystalline chlorine transforms into the tetragonal one, which has a space group P4 2 /ncm and lattice parameters a=8.56 and c=6.12 .

Solubility

Solvent	Solubility g/100 g
Benzene	Soluble
Water (0 °C)	1,48
Water (20°C)	0,96
Water (25°C)	0,65
Water (40°C)	0,46
Water (60°C)	0,38
Water (80°C)	0,22
Carbon tetrachloride (0 °C)	31,4
Carbon tetrachloride (19 °C)	17,61
Carbon tetrachloride (40 °C)	11
Chloroform	Highly soluble
TiCl 4 , SiCl 4 , SnCl 4	Soluble

In the light or when heated, it actively reacts (sometimes with an explosion) with hydrogen by a radical mechanism. Mixtures of chlorine with hydrogen, containing from 5.8 to 88.3% hydrogen, explode when irradiated with the formation of hydrogen chloride. A mixture of chlorine and hydrogen in small concentrations burns with a colorless or yellow-green flame. The maximum temperature of the hydrogen-chlorine flame is 2200 °C.:

Cl 2 + H 2 → 2HCl 5Cl 2 + 2P → 2PCl 5 2S + Cl 2 → S 2 Cl 2 Cl 2 + 3F 2 (ex.) → 2ClF 3

Other properties

Cl 2 + CO → COCl 2

When dissolved in water or alkalis, chlorine dismutates, forming hypochlorous (and when heated perchloric) and hydrochloric acids, or their salts:

Cl 2 + H 2 O → HCl + HClO 3Cl 2 + 6NaOH → 5NaCl + NaClO 3 + 3H 2 O Cl 2 + Ca(OH) 2 → CaCl(OCl) + H 2 O 4NH 3 + 3Cl 2 → NCl 3 + 3NH 4Cl

Oxidizing properties of chlorine

Cl 2 + H 2 S → 2HCl + S

Reactions with organic substances

CH 3 -CH 3 + Cl 2 → C 2 H 6-x Cl x + HCl

Attaches to unsaturated compounds by multiple bonds:

CH 2 \u003d CH 2 + Cl 2 → Cl-CH 2 -CH 2 -Cl

Aromatic compounds replace a hydrogen atom with chlorine in the presence of catalysts (for example, AlCl 3 or FeCl 3):

C 6 H 6 + Cl 2 → C 6 H 5 Cl + HCl

Chlorine methods for producing chlorine

Industrial Methods

Initially, the industrial method for producing chlorine was based on the Scheele method, that is, the reaction of pyrolusite with hydrochloric acid:

MnO 2 + 4HCl → MnCl 2 + Cl 2 + 2H 2 O 2NaCl + 2H 2 O → H 2 + Cl 2 + 2NaOH Anode: 2Cl - - 2e - → Cl 2 0 Cathode: 2H 2 O + 2e - → H 2 + 2OH-

Since the electrolysis of water takes place in parallel with the electrolysis of sodium chloride, the total equation can be expressed as follows:

1.80 NaCl + 0.50 H 2 O → 1.00 Cl 2 + 1.10 NaOH + 0.03 H 2

Three variants of the electrochemical method for producing chlorine are used. Two of them are electrolysis with a solid cathode: diaphragm and membrane methods, the third is electrolysis with a liquid cathode (mercury production method). In a number of electrochemical production methods, the easiest and most convenient method is electrolysis with a mercury cathode, but this method causes significant harm. environment as a result of evaporation and leakage of metallic mercury.

Diaphragm method with solid cathode

The cavity of the cell is divided by a porous asbestos partition - diaphragm - into the cathode and anode space, where the cathode and anode of the cell are respectively located. Therefore, such an electrolyzer is often called diaphragm electrolysis, and the production method is diaphragm electrolysis. A stream of saturated anolyte (NaCl solution) continuously enters the anode space of the diaphragm cell. As a result of the electrochemical process, chlorine is released at the anode due to the decomposition of halite, and hydrogen is released at the cathode due to the decomposition of water. In this case, the near-cathode zone is enriched with sodium hydroxide.

Membrane method with solid cathode

The membrane method is essentially similar to the diaphragm method, but the anode and cathode spaces are separated by a cation-exchange polymer membrane. The membrane production method is more efficient than the diaphragm method, but it is more difficult to use.

Mercury method with liquid cathode

The process is carried out in an electrolytic bath, which consists of an electrolyzer, a decomposer and a mercury pump, interconnected by communications. In the electrolytic bath, under the action of a mercury pump, mercury circulates, passing through the electrolyzer and the decomposer. The cathode of the cell is a stream of mercury. Anodes - graphite or low wear. Together with mercury, a stream of anolyte, a solution of sodium chloride, continuously flows through the electrolyzer. As a result of the electrochemical decomposition of chloride, chlorine molecules are formed at the anode, and the released sodium dissolves in mercury at the cathode, forming an amalgam.

Laboratory methods

In laboratories, to obtain chlorine, processes based on the oxidation of hydrogen chloride with strong oxidizing agents (for example, manganese (IV) oxide, potassium permanganate, potassium dichromate) are usually used:

2KMnO 4 + 16HCl → 2KCl + 2MnCl 2 + 5Cl 2 +8H 2 O K 2 Cr 2 O 7 + 14HCl → 3Cl 2 + 2KCl + 2CrCl 3 + 7H 2 O

Chlorine storage

The produced chlorine is stored in special “tanks” or pumped into high-pressure steel cylinders. Cylinders with liquid chlorine under pressure have a special color - marsh color. It should be noted that during prolonged use of chlorine cylinders, extremely explosive nitrogen trichloride accumulates in them, and therefore, from time to time, chlorine cylinders must be routinely flushed and cleaned from nitrogen chloride.

Chlorine quality standards

According to GOST 6718-93 “Liquid chlorine. Specifications” the following grades of chlorine are produced

Application

Chlorine is used in many industries, science and domestic needs:

• In the production of polyvinyl chloride, plastic compounds, synthetic rubber, which are used to make: insulation for wires, window profiles, packaging materials, clothes and shoes, linoleum and gramophone records, varnishes, equipment and foam plastics, toys, instrument parts, building materials. Polyvinyl chloride is produced by polymerizing vinyl chloride, which today is most often obtained from ethylene in a chlorine-balanced method through an intermediate 1,2-dichloroethane.
• The bleaching properties of chlorine have been known since ancient times, although it is not chlorine itself that “bleaches”, but atomic oxygen, which is formed during the decomposition of hypochlorous acid: Cl 2 + H 2 O → HCl + HClO → 2HCl + O .. This method of bleaching fabrics, paper, Cardboard has been used for centuries.
• Production of organochlorine insecticides - substances that kill insects harmful to crops, but are safe for plants. A significant part of the produced chlorine is spent on obtaining plant protection products. One of the most important insecticides is hexachlorocyclohexane (often referred to as hexachlorane). This substance was first synthesized back in 1825 by Faraday, but found practical application only after more than 100 years - in the 30s of our century.
• It was used as a chemical warfare agent, as well as for the production of other chemical warfare agents: mustard gas, phosgene.
• For water disinfection - "chlorination". The most common method of disinfecting drinking water; is based on the ability of free chlorine and its compounds to inhibit the enzyme systems of microorganisms that catalyze redox processes. For the disinfection of drinking water, chlorine, chlorine dioxide, chloramine and bleach are used. SanPiN 2.1.4.1074-01 establishes the following limits (corridor) for the permissible content of free residual chlorine in drinking water from centralized water supply 0.3 - 0.5 mg / l. A number of scientists and even politicians in Russia criticize the very concept of chlorination of tap water, but they cannot offer an alternative to the disinfecting aftereffect of chlorine compounds. The materials from which water pipes are made interact differently with chlorinated tap water. Free chlorine in tap water significantly reduces the life of pipelines based on polyolefins: polyethylene pipes of various types, including cross-linked polyethylene, more commonly known as PEX (PEX, PE-X). In the USA, in order to control the admission of pipelines made of polymeric materials for use in water supply systems with chlorinated water, 3 standards were forced to be adopted: ASTM F2023 for pipes, membranes and skeletal muscles. These channels perform important functions in the regulation of fluid volume, transepithelial ion transport and stabilization of membrane potentials, and are involved in maintaining cell pH. Chlorine accumulates in visceral tissue, skin and skeletal muscles. Chlorine is absorbed mainly in the large intestine. The absorption and excretion of chlorine are closely related to sodium ions and bicarbonates, to a lesser extent with mineralocorticoids and the activity of Na + /K + - ATP-ase. 10-15% of all chlorine is accumulated in cells, from this amount from 1/3 to 1/2 - in erythrocytes. About 85% of chlorine is in the extracellular space. Chlorine is excreted from the body mainly with urine (90-95%), feces (4-8%) and through the skin (up to 2%). The excretion of chlorine is associated with sodium and potassium ions, and reciprocally with HCO 3 - (acid-base balance).

  A person consumes 5-10 g of NaCl per day. The minimum human need for chlorine is about 800 mg per day. The infant receives the necessary amount of chlorine through the mother's milk, which contains 11 mmol / l of chlorine. NaCl is necessary for the production of hydrochloric acid in the stomach, which promotes digestion and the destruction of pathogenic bacteria. At present, the role of chlorine in the occurrence of certain diseases in humans is not well understood, mainly due to the small number of studies. Suffice it to say that even recommendations on the daily intake of chlorine have not been developed. Human muscle tissue contains 0.20-0.52% chlorine, bone - 0.09%; in the blood - 2.89 g / l. In the body of an average person (body weight 70 kg) 95 g of chlorine. Every day with food, a person receives 3-6 g of chlorine, which in excess covers the need for this element.

  Chlorine ions are vital for plants. Chlorine is involved in energy exchange in plants by activating oxidative phosphorylation. It is necessary for the formation of oxygen in the process of photosynthesis by isolated chloroplasts, stimulates auxiliary processes of photosynthesis, primarily those associated with the accumulation of energy. Chlorine has a positive effect on the absorption of oxygen, potassium, calcium, and magnesium compounds by the roots. Excessive concentration of chlorine ions in plants can have and negative side, for example, reduce the content of chlorophyll, reduce the activity of photosynthesis, retard the growth and development of plants Baskunchak chlorine). Chlorine was one of the first chemical poisons used

  – With the help of analytical laboratory equipment, laboratory and industrial electrodes, in particular: reference electrodes ESr-10101 analyzing the content of Cl- and K +.

  Chlorine requests, we are found by chlorine requests

  Interaction, poisoning, water, reactions and obtaining chlorine

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In the west of Flanders lies a tiny town. Nevertheless, its name is known throughout the world and will long remain in the memory of mankind as a symbol of one of the greatest crimes against humanity. This town is Ypres. Crecy (in the Battle of Crecy in 1346, the English troops used firearms for the first time in Europe.) - Ypres - Hiroshima - milestones on the way to turning the war into a giant destruction machine.

At the beginning of 1915, the so-called Ypres ledge formed on the western front line. The allied Anglo-French troops northeast of Ypres wedged into the territory comma of the German army. The German command decided to launch a counterattack and level the front line. On the morning of April 22, when a flat northeast blew, the Germans began an unusual preparation for the offensive - they carried out the first gas attack in the history of wars. On the Ypres sector of the front, 6,000 cylinders of chlorine were simultaneously opened. Within five minutes, a huge, weighing 180 tons, poisonous yellow-green cloud formed, which slowly moved towards the enemy's trenches.

Nobody expected this. The troops of the French and British were preparing for an attack, for artillery shelling, the soldiers dug in securely, but in front of the destructive chlorine cloud they were absolutely unarmed. The deadly gas penetrated into all the cracks, into all the shelters. The results of the first chemical attack (and the first violation of the 1907 Hague Convention on the Non-Use of Poisonous Substances!) were stunning - chlorine struck about 15,000 people, and about 5,000 died. And all this - in order to level the front line 6 km long! Two months later, the Germans launched a chlorine attack on the eastern front as well. And two years later, Ypres increased its notoriety. During a heavy battle on July 12, 1917, a poisonous substance, later called mustard gas, was used for the first time in the area of ​​\u200b\u200bthis city. Mustard is a derivative of chlorine, dichlorodiethyl sulfide.

We recalled these episodes of history, connected with one small town and one chemical element, in order to show how dangerous element No. 17 can be in the hands of militant madmen. This is the darkest page in the history of chlorine.

But it would be completely wrong to see in chlorine only a poisonous substance and a raw material for the production of other poisonous substances...

History of chlorine

The history of elemental chlorine is relatively short, dating back to 1774. The history of chlorine compounds is as old as the world. Suffice it to recall that sodium chloride is table salt. And, apparently, even in prehistoric times, the ability of salt to preserve meat and fish was noticed.

The most ancient archaeological finds - evidence of the use of salt by humans date back to about 3...4 millennium BC. And the most ancient description of the extraction of rock salt is found in the writings of the Greek historian Herodotus (V century BC). Herodotus describes the mining of rock salt in Libya. In the oasis of Sinah in the center of the Libyan desert was the famous temple of the god Ammon-Ra. That is why Libya was called "Ammonia", and the first name of rock salt was "sal ammoniacum". Later, starting around the thirteenth century. AD, this name was assigned to ammonium chloride.

Pliny the Elder's Natural History describes a method for separating gold from base metals by calcining with salt and clay. And one of the first descriptions of the purification of sodium chloride is found in the writings of the great Arab physician and alchemist Jabir ibn Hayyan (in European spelling - Geber).

It is very likely that alchemists also encountered elemental chlorine, since in the countries of the East already in the 9th, and in Europe in the 13th century. "royal vodka" was known - a mixture of hydrochloric and nitric acids. The book Hortus Medicinae by the Dutchman Van Helmont, published in 1668, says that when ammonium chloride and nitric acid are heated together, a certain gas is obtained. Based on the description, this gas is very similar to chlorine.

Chlorine was first described in detail by the Swedish chemist Scheele in his treatise on pyrolusite. By heating the mineral pyrolusite with hydrochloric acid, Scheele noticed the smell characteristic of aqua regia, collected and studied the yellow-green gas that gave rise to this smell, and studied its interaction with certain substances. Scheele was the first to discover the effect of chlorine on gold and cinnabar (in the latter case, sublimate is formed) and the bleaching properties of chlorine.

Scheele did not consider the newly discovered gas to be a simple substance and called it "dephlogistinated hydrochloric acid". talking modern language, Scheele, and after him other scientists of that time believed that the new gas was hydrochloric acid oxide.

Somewhat later, Bertholet and Lavoisier suggested that this gas be considered an oxide of some new element, murium. For three and a half decades, chemists have unsuccessfully tried to isolate the unknown murium.

A supporter of "murium oxide" was at first also Davy, who in 1807 decomposed table salt with an electric current into the alkali metal sodium and yellow-green gas. However, three years later, after many fruitless attempts to obtain muria, Davy came to the conclusion that the gas discovered by Scheele was a simple substance, an element, and called it chloric gas or chlorine (from the Greek χλωροζ - yellow-green). And three years later, Gay-Lussac gave the new element a shorter name - chlorine. True, back in 1811, the German chemist Schweiger proposed another name for chlorine - “halogen” (literally, it translates as salt), but this name did not take root at first, and later became common for a whole group of elements, which includes chlorine.

"Personal card" of chlorine

To the question, what is chlorine, you can give at least a dozen answers. First, it is a halogen; secondly, one of the strongest oxidizing agents; thirdly, an extremely poisonous gas; fourthly, the most important product of the main chemical industry; fifthly, raw materials for the production of plastics and pesticides, rubber and artificial fibers, dyes and medicines; sixth, the substance with which titanium and silicon, glycerin and fluoroplast are obtained; seventh, a means for purifying drinking water and bleaching fabrics ...

This listing could be continued.

Under normal conditions, elemental chlorine is a rather heavy yellow-green gas with a pungent characteristic odor. The atomic weight of chlorine is 35.453, and the molecular weight is 70.906, because the chlorine molecule is diatomic. One liter of gaseous chlorine under normal conditions (temperature 0 ° C and pressure 760 mmHg) weighs 3.214 g. When cooled to -34.05 ° C, chlorine condenses into a yellow liquid (density 1.56 g / cm 3), and hardens at a temperature of -101.6°C. Under increased pressure, chlorine can be liquidized at higher temperatures up to +144°C. Chlorine is highly soluble in dichloroethane and some other chlorine-containing organic solvents.

Element number 17 is very active - it directly connects with almost all elements of the periodic system. Therefore, in nature, it occurs only in the form of compounds. The most common minerals containing chlorine, halite NaCI, sylvinite KCl NaCl, bischofite MgCl 2 6H 2 O, carnallite KCl MgCl 2 6H 2 O, kainite KCl MgSO 4 3H 2 O. This is their first of all "wine ” (or “merit”) that the chlorine content in the earth’s crust is 0.20% by weight. For non-ferrous metallurgy, some relatively rare chlorine-containing minerals are very important, for example, horn silver AgCl.

In terms of electrical conductivity, liquid chlorine ranks among the strongest insulators: it conducts current almost a billion times worse than distilled water, and 10 22 times worse than silver.

The speed of sound in chlorine is about one and a half times less than in air.

And finally - about the isotopes of chlorine.

Now nine isotopes of this element are known, but only two are found in nature - chlorine-35 and chlorine-37. The first is about three times more than the second.

The remaining seven isotopes were obtained artificially. The shortest-lived of them - 32 Cl has a half-life of 0.306 seconds, and the longest-lived - 36 Cl - 310 thousand years.

How is chlorine obtained?

The first thing you notice when you get to the chlorine plant is the numerous power lines. Chlorine production consumes a lot of electricity - it is needed in order to decompose natural chlorine compounds.

Naturally, the main chlorine raw material is rock salt. If the chlorine plant is located near the river, then the salt is delivered not by rail, but by barges - it's more economical. Salt is an inexpensive product, but a lot of it is consumed: to get a ton of chlorine, you need about 1.7 ... 1.8 tons of salt.

Salt goes to warehouses. Three-six-month stocks of raw materials are stored here - chlorine production, as a rule, is large-tonnage.

Salt is crushed and dissolved in warm water. This brine is pumped through the pipeline to the cleaning shop, where in huge tanks, the height of a three-story house, the brine is cleaned from impurities of calcium and magnesium salts and clarified (allowed to settle). A pure concentrated solution of sodium chloride is pumped to the main chlorine production shop - to the electrolysis shop.

In an aqueous solution, salt molecules are converted into Na + and Cl - ions. The Cl ion differs from the chlorine atom only in that it has one extra electron. This means that in order to obtain elemental chlorine, it is necessary to tear off this extra electron. This happens in the cell on a positively charged electrode (anode). Electrons seem to be “sucked off” from it: 2Cl - → Cl 2 + 2 ē . The anodes are made of graphite, because any metal (except platinum and its analogues), taking away excess electrons from chlorine ions, quickly corrodes and collapses.

There are two types of technological design of chlorine production: diaphragm and mercury. In the first case, a perforated iron sheet serves as the cathode, and the cathode and anode spaces of the cell are separated by an asbestos diaphragm. On the iron cathode, hydrogen ions are discharged and an aqueous solution of caustic soda is formed. If mercury is used as a cathode, then sodium ions are discharged on it and sodium amalgam is formed, which is then decomposed by water. Hydrogen and caustic soda are obtained. In this case, a separating diaphragm is not needed, and the alkali is more concentrated than in diaphragm electrolyzers.

So, the production of chlorine is simultaneously the production of caustic soda and hydrogen.

Hydrogen is removed through metal pipes, and chlorine through glass or ceramic pipes. Freshly prepared chlorine is saturated with water vapor and is therefore particularly aggressive. Subsequently, it is first cooled with cold water in high towers, lined with ceramic tiles from the inside and filled with ceramic nozzles (the so-called Raschig rings), and then dried with concentrated sulfuric acid. It is the only chlorine desiccant and one of the few liquids that chlorine interacts with.

Dry chlorine is no longer so aggressive, it does not destroy, for example, steel equipment.

Chlorine is usually transported in a liquid state in railway tanks or cylinders under pressure up to 10 atm.

In Russia, the production of chlorine was first organized as early as 1880 at the Bondyuzhsky plant. Chlorine was then obtained in principle in the same way that Scheele had obtained it in his time - by reacting hydrochloric acid with pyrolusite. All chlorine produced was used to produce bleach. In 1900, for the first time in Russia, a workshop for the electrolytic production of chlorine was put into operation at the Donsoda plant. The capacity of this workshop was only 6 thousand tons per year. In 1917, all chlorine plants in Russia produced 12,000 tons of chlorine. And in 1965, about 1 million tons of chlorine were produced in the USSR ...

One of many

All the variety of practical applications of chlorine can be expressed without much stretch in one phrase: chlorine is necessary for the production of chlorine products, i.e. substances containing “bound” chlorine. But speaking of these same chlorine products, you can’t get off with one phrase. They are very different - both in properties and in purpose.

The limited volume of our article does not allow us to talk about all the compounds of chlorine, but without a story about at least some substances that require chlorine, our “portrait” of element No. 17 would be incomplete and unconvincing.

Take, for example, organochlorine insecticides - substances that kill harmful insects, but are safe for plants. A significant part of the produced chlorine is spent on obtaining plant protection products.

One of the most important insecticides is hexachlorocyclohexane (often referred to as hexachlorane). This substance was first synthesized back in 1825 by Faraday, but found practical application only after more than 100 years - in the 30s of our century.

Now hexachlorane is obtained by chlorinating benzene. Like hydrogen, benzene reacts very slowly with chlorine in the dark (and in the absence of catalysts), but in bright light, the benzene chlorination reaction (C 6 H 6 + 3Cl 2 → C 6 H 6 Cl 6) proceeds quite quickly.

Hexachloran, like many other insecticides, is used in the form of dusts with fillers (talc, kaolin), or in the form of suspensions and emulsions, or, finally, in the form of aerosols. Hexachloran is especially effective in seed dressing and in pest control of vegetable and fruit crops. The consumption of hexachlorane is only 1...3 kg per hectare, the economic effect of its use is 10...15 times higher than the costs. Unfortunately, hexachlorane is not harmless to humans...

PVC

If you ask any student to list the plastics known to him, he will be one of the first to name polyvinyl chloride (otherwise, vinyl plastic). From the point of view of a chemist, PVC (as polyvinyl chloride is often referred to in the literature) is a polymer in the molecule of which hydrogen and chlorine atoms are strung on a chain of carbon atoms:

There may be several thousand links in this chain.

And from a consumer point of view, PVC is insulation for wires and raincoats, linoleum and gramophone records, protective varnishes and packaging materials, chemical equipment and foam plastics, toys and instrument parts.

Polyvinyl chloride is formed during the polymerization of vinyl chloride, which is most often obtained by treating acetylene with hydrogen chloride: HC ≡ CH + HCl → CH 2 = CHCl. There is another way to obtain vinyl chloride - thermal cracking of dichloroethane.

CH 2 Cl - CH 2 Cl → CH 2 \u003d CHCl + HCl. Of interest is the combination of these two methods, when HCl is used in the production of vinyl chloride by the acetylene method, which is released during the cracking of dichloroethane.

Vinyl chloride is a colorless gas with a pleasant, somewhat heady, ethereal odor that polymerizes easily. To obtain a polymer, liquid vinyl chloride is injected under pressure into warm water, where it is crushed into tiny droplets. So that they do not merge, a little gelatin or polyvinyl alcohol is added to the water, and in order for the polymerization reaction to begin to develop, the polymerization initiator, benzoyl peroxide, is also introduced there. After a few hours, the droplets harden and a suspension of the polymer in water is formed. The polymer powder is separated on a filter or centrifuge.

Polymerization usually occurs at a temperature of 40 to 60°C, and the lower the polymerization temperature, the longer the resulting polymer molecules...

We talked about only two substances, for which element No. 17 is required. Only about two out of many hundreds. There are many such examples. And they all say that chlorine is not only a poisonous and dangerous gas, but a very important, very useful element.

Elementary calculation

When chlorine is obtained by electrolysis of a sodium chloride solution, hydrogen and sodium hydroxide are simultaneously obtained: 2NACl + 2H 2 O \u003d H 2 + Cl 2 + 2NaOH. Of course, hydrogen is a very important chemical product, but there are cheaper and more convenient ways to produce this substance, such as the conversion of natural gas ... But caustic soda is obtained almost exclusively by electrolysis of sodium chloride solutions - other methods account for less than 10%. Since the production of chlorine and NaOH are completely interconnected (as follows from the reaction equation, the production of one gram-molecule - 71 g of chlorine - is invariably accompanied by the production of two gram-molecules - 80 g of electrolytic alkali), knowing the performance of the workshop (or plant, or state) in terms of alkali , you can easily calculate how much chlorine it produces. Each ton of NaOH is "accompanied" by 890 kg of chlorine.

Oh, and lube!

Concentrated sulfuric acid is practically the only liquid that does not interact with chlorine. Therefore, for compressing and pumping chlorine, factories use pumps in which sulfuric acid plays the role of a working fluid and at the same time a lubricant.

Pseudonym of Friedrich Wöhler

Investigating the interaction of organic substances with chlorine, the French chemist of the XIX century. Jean Dumas made an amazing discovery: chlorine is able to replace hydrogen in the molecules of organic compounds. For example, during the chlorination of acetic acid, first one hydrogen of the methyl group is replaced by chlorine, then another, a third ... But the most striking thing was that the chemical properties of chloroacetic acids differed little from acetic acid itself. The class of reactions discovered by Dumas was completely inexplicable by the then prevailing electrochemical hypothesis and the theory of Berzelius radicals (in the words of the French chemist Laurent, the discovery of chloroacetic acid was like a meteor that destroyed the whole old school). Berzelius, his students and followers vigorously disputed the correctness of Dumas' work. A mocking letter from the famous German chemist Friedrich Wöhler under the pseudonym S.C.H. appeared in the German journal Annalen der Chemie und Pharmacie. Windier (in German "Schwindler" means "liar", "deceiver"). It reported that the author was able to replace in fiber (C 6 H 10 O 5) and all carbon atoms. hydrogen and oxygen to chlorine, and the properties of fiber did not change. And what now in London they make warm girdles from cotton wool, consisting ... of pure chlorine.

Chlorine and water

Chlorine is visibly soluble in water. At 20°C, 2.3 volumes of chlorine dissolve in one volume of water. Aqueous solutions of chlorine (chlorine water) are yellow. But over time, especially when stored in the light, they gradually discolor. This is explained by the fact that dissolved chlorine partially interacts with water, hydrochloric and hypochlorous acids are formed: Cl 2 + H 2 O → HCl + HOCl. The latter is unstable and gradually decomposes into HCl and oxygen. Therefore, a solution of chlorine in water gradually turns into a solution of hydrochloric acid.

But at low temperatures, chlorine and water form a crystalline hydrate of an unusual composition - Cl 2 5 3 / 4 H 2 O. These greenish-yellow crystals (stable only at temperatures below 10 ° C) can be obtained by passing chlorine through ice water. The unusual formula is explained by the structure of the crystalline hydrate, and it is determined primarily by the structure of ice. In the crystal lattice of ice, H 2 O molecules can be arranged in such a way that regularly spaced voids appear between them. The elementary cubic cell contains 46 water molecules, between which there are eight microscopic voids. In these voids, chlorine molecules settle. The exact formula of chlorine hydrate should therefore be written as follows: 8Cl 2 46H 2 O.

Chlorine poisoning

The presence of about 0.0001% chlorine in the air irritates the mucous membranes. Constant exposure to such an atmosphere can lead to bronchial disease, sharply impairs appetite, and gives a greenish tint to the skin. If the chlorine content in the air is 0.1 ° / o, then acute poisoning can occur, the first sign of which is bouts of severe coughing. In case of chlorine poisoning, absolute rest is necessary; it is useful to inhale oxygen, or ammonia (sniffing ammonia), or vapors of alcohol with ether. According to existing sanitary standards, the content of chlorine in the air of industrial premises should not exceed 0.001 mg/l, i.e. 0.00003%.

Not only poison

"Everyone knows that wolves are greedy." That chlorine is poisonous, too. However, in small doses, poisonous chlorine can sometimes serve as an antidote. So, victims of hydrogen sulfide are given to sniff unstable bleach. By interacting, the two poisons are mutually neutralized.

Chlorine analysis

To determine the chlorine content, an air sample is passed through absorbers with an acidified solution of potassium iodide. (Chlorine displaces iodine, the amount of the latter is easily determined by titration with a solution of Na 2 S 2 O 3). To determine the microquantities of chlorine in the air, a colorimetric method is often used, based on a sharp change in the color of certain compounds (benzidine, orthotoluidine, methyl orange) during their oxidation with chlorine. For example, a colorless acidified solution of benzidine turns yellow, and a neutral one turns blue. The color intensity is proportional to the amount of chlorine.

In 1774, Carl Scheele, a chemist from Sweden, first obtained chlorine, but it was believed that this was not a separate element, but a type of hydrochloric acid (calorizator). Elemental chlorine was obtained at the beginning of the 19th century by G. Davy, who decomposed table salt into chlorine and sodium by electrolysis.

Chlorine (from the Greek χλωρός - green) is an element of the XVII group of the periodic table of chemical elements of D.I. Mendeleev, has an atomic number of 17 and an atomic mass of 35.452. The accepted designation Cl (from the Latin Chlorum).

Being in nature

Chlorine is the most common halogen in the earth's crust, most often in the form of two isotopes. Due to its chemical activity, it is found only in the form of compounds of many minerals.

Chlorine is a poisonous yellow-green gas with a pungent odor and a sweetish taste. It was chlorine that, after its discovery, was proposed to be called halogen, it is included in the group of the same name as one of the most chemically active non-metals.

Daily requirement for chlorine

Normally, a healthy adult should receive 4-6 g of chlorine per day, the need for it increases with active physical exertion or hot weather (with increased sweating). Usually daily allowance The body receives from food with a balanced diet.

The main supplier of chlorine to the body is table salt - especially if it is not subjected to heat treatment, so it is better to salt already prepared dishes. Also contain chlorine, seafood, meat, and, and,.

Interaction with others

The acid-base and water balance of the body is regulated by chlorine.

Signs of a lack of chlorine

The lack of chlorine is caused by processes that lead to dehydration of the body - severe sweating in the heat or during physical exertion, vomiting, diarrhea and some diseases of the urinary system. Signs of a lack of chlorine are lethargy and drowsiness, muscle weakness, pronounced dry mouth, loss of taste, lack of appetite.

Signs of excess chlorine

Signs of excess chlorine in the body are: increased blood pressure, dry cough, pain in the head and chest, pain in the eyes, lacrimation, activity disorders gastrointestinal tract. As a rule, an excess of chlorine can be caused by drinking ordinary tap water that goes through the chlorine disinfection process and occurs in workers in industries that are directly related to the use of chlorine.

Chlorine in the human body:

• regulates water and acid-base balance,
• removes fluid and salts from the body in the process of osmoregulation,
• stimulates normal digestion,
• normalizes the state of erythrocytes,
• cleanses the liver of fat.

The main use of chlorine is the chemical industry, where it is used to produce polyvinyl chloride, foam plastic, packaging materials, as well as chemical warfare agents and fertilizers for plants. Disinfection of drinking water with chlorine is practically the only available way to purify water.

The physical properties of chlorine are considered: the density of chlorine, its thermal conductivity, specific heat capacity and dynamic viscosity at various temperatures. The physical properties of Cl 2 are presented in the form of tables for the liquid, solid and gaseous state of this halogen.

Basic physical properties of chlorine

Chlorine is included in group VII of the third period of the periodic system of elements at number 17. It belongs to the halogen subgroup, has relative atomic and molecular weights of 35.453 and 70.906, respectively. At temperatures above -30°C, chlorine is a greenish-yellow gas with a characteristic pungent, irritating odor. It liquefies easily under ordinary pressure (1.013·10 5 Pa) when cooled to -34°C and forms a clear amber liquid that solidifies at -101°C.

Due to its high reactivity, free chlorine does not occur in nature, but exists only in the form of compounds. It is found mainly in the mineral halite (), it is also part of such minerals as: sylvin (KCl), carnallite (KCl MgCl 2 6H 2 O) and sylvinite (KCl NaCl). The content of chlorine in the earth's crust approaches 0.02% of the total number of atoms in the earth's crust, where it is in the form of two isotopes 35 Cl and 37 Cl in a percentage of 75.77% 35 Cl and 24.23% 37 Cl.

Physical properties of chlorine - table of main indicators

Property	Meaning
Melting point, °С	-100,5
Boiling point, °C	-30,04
Critical temperature, °C	144
Critical pressure, Pa	77.1 10 5
Critical density, kg / m 3	573
Gas density (at 0°С and 1.013 10 5 Pa), kg/m 3	3,214
Density of saturated steam (at 0°С and 3.664 10 5 Pa), kg/m 3	12,08
Density of liquid chlorine (at 0 ° C and 3.664 10 5 Pa), kg / m 3	1468
Density of liquid chlorine (at 15.6 ° C and 6.08 10 5 Pa), kg / m 3	1422
Density of solid chlorine (at -102°С), kg/m 3	1900
Relative density in air of gas (at 0°C and 1.013 10 5 Pa)	2,482
Relative air density of saturated steam (at 0°C and 3.664 10 5 Pa)	9,337
Relative density of liquid chlorine at 0°С (for water at 4°С)	1,468
Specific volume of gas (at 0°С and 1.013 10 5 Pa), m 3 /kg	0,3116
Specific volume of saturated steam (at 0°C and 3.664 10 5 Pa), m 3 /kg	0,0828
Specific volume of liquid chlorine (at 0°C and 3.664 10 5 Pa), m 3 /kg	0,00068
Chlorine vapor pressure at 0°C, Pa	3.664 10 5
Dynamic viscosity of gas at 20°C, 10 -3 Pa s	0,013
Dynamic viscosity of liquid chlorine at 20°C, 10 -3 Pa s	0,345
Melting heat of solid chlorine (at the melting point), kJ/kg	90,3
Heat of vaporization (at boiling point), kJ/kg	288
Heat of sublimation (at melting point), kJ/mol	29,16
Molar heat capacity C p of gas (at -73…5727°C), J/(mol K)	31,7…40,6
Molar heat capacity C p of liquid chlorine (at -101…-34°C), J/(mol K)	67,1…65,7
Gas thermal conductivity coefficient at 0°C, W/(m K)	0,008
Thermal conductivity coefficient of liquid chlorine at 30°C, W/(m K)	0,62
Gas enthalpy, kJ/kg	1,377
Enthalpy of saturated steam, kJ/kg	1,306
Enthalpy of liquid chlorine, kJ/kg	0,879
Refractive index at 14°C	1,367
Specific conductivity at -70°C, Sm/m	10 -18
Electron affinity, kJ/mol	357
Ionization energy, kJ/mol	1260

Density of chlorine

Under normal conditions, chlorine is a heavy gas with a density approximately 2.5 times greater than . Density of gaseous and liquid chlorine under normal conditions (at 0 ° C) is equal to 3.214 and 1468 kg / m 3, respectively. When liquid or gaseous chlorine is heated, its density decreases due to an increase in volume due to thermal expansion.

Density of chlorine gas

The table shows the density of chlorine in the gaseous state at various temperatures (in the range from -30 to 140°C) and normal atmospheric pressure (1.013·10 5 Pa). The density of chlorine changes with temperature - when heated, it decreases. For example, at 20 ° C, the density of chlorine is 2.985 kg / m 3, and when the temperature of this gas rises to 100 ° C, the density value decreases to a value of 2.328 kg / m 3.

Density of gaseous chlorine at various temperatures

t, °С	ρ, kg / m 3	t, °С	ρ, kg / m 3
-30	3,722	60	2,616
-20	3,502	70	2,538
-10	3,347	80	2,464
0	3,214	90	2,394
10	3,095	100	2,328
20	2,985	110	2,266
30	2,884	120	2,207
40	2,789	130	2,15
50	2,7	140	2,097

With increasing pressure, the density of chlorine increases. The tables below show the density of gaseous chlorine in the temperature range from -40 to 140°C and pressure from 26.6·10 5 to 213·10 5 Pa. With increasing pressure, the density of chlorine in the gaseous state increases proportionally. For example, an increase in the pressure of chlorine from 53.2·10 5 to 106.4·10 5 Pa at a temperature of 10°C leads to a twofold increase in the density of this gas.

The density of gaseous chlorine at various temperatures and pressures is from 0.26 to 1 atm.

↓ t, °C | P, kPa →	26,6	53,2	79,8	101,3
-40	0,9819	1,996	—	—
-30	0,9402	1,896	2,885	3,722
-20	0,9024	1,815	2,743	3,502
-10	0,8678	1,743	2,629	3,347
0	0,8358	1,678	2,528	3,214
10	0,8061	1,618	2,435	3,095
20	0,7783	1,563	2,35	2,985
30	0,7524	1,509	2,271	2,884
40	0,7282	1,46	2,197	2,789
50	0,7055	1,415	2,127	2,7
60	0,6842	1,371	2,062	2,616
70	0,6641	1,331	2	2,538
80	0,6451	1,292	1,942	2,464
90	0,6272	1,256	1,888	2,394
100	0,6103	1,222	1,836	2,328
110	0,5943	1,19	1,787	2,266
120	0,579	1,159	1,741	2,207
130	0,5646	1,13	1,697	2,15
140	0,5508	1,102	1,655	2,097

The density of gaseous chlorine at various temperatures and pressures is from 1.31 to 2.1 atm.

↓ t, °C | P, kPa →	133	160	186	213
-20	4,695	5,768	—	—
-10	4,446	5,389	6,366	7,389
0	4,255	5,138	6,036	6,954
10	4,092	4,933	5,783	6,645
20	3,945	4,751	5,565	6,385
30	3,809	4,585	5,367	6,154
40	3,682	4,431	5,184	5,942
50	3,563	4,287	5,014	5,745
60	3,452	4,151	4,855	5,561
70	3,347	4,025	4,705	5,388
80	3,248	3,905	4,564	5,225
90	3,156	3,793	4,432	5,073
100	3,068	3,687	4,307	4,929
110	2,985	3,587	4,189	4,793
120	2,907	3,492	4,078	4,665
130	2,832	3,397	3,972	4,543
140	2,761	3,319	3,87	4,426

Density of liquid chlorine

Liquid chlorine can exist in a relatively narrow temperature range, the boundaries of which lie from minus 100.5 to plus 144°C (that is, from the melting point to the critical temperature). Above a temperature of 144 ° C, chlorine will not go into a liquid state at any pressure. The density of liquid chlorine in this temperature range varies from 1717 to 573 kg/m 3 .

Density of liquid chlorine at various temperatures

t, °С	ρ, kg / m 3	t, °С	ρ, kg / m 3
-100	1717	30	1377
-90	1694	40	1344
-80	1673	50	1310
-70	1646	60	1275
-60	1622	70	1240
-50	1598	80	1199
-40	1574	90	1156
-30	1550	100	1109
-20	1524	110	1059
-10	1496	120	998
0	1468	130	920
10	1438	140	750
20	1408	144	573

Specific heat capacity of chlorine

The specific heat capacity of gaseous chlorine C p in kJ / (kg K) in the temperature range from 0 to 1200 ° C and normal atmospheric pressure can be calculated by the formula:

where T is the absolute temperature of chlorine in degrees Kelvin.

It should be noted that under normal conditions, the specific heat capacity of chlorine is 471 J/(kg K) and increases upon heating. The increase in heat capacity at temperatures above 500°C becomes insignificant, and at high temperatures the specific heat capacity of chlorine remains virtually unchanged.

The table shows the results of calculating the specific heat capacity of chlorine using the above formula (the calculation error is about 1%).

Specific heat capacity of chlorine gas as a function of temperature

t, °С	C p , J/(kg K)	t, °С	C p , J/(kg K)
0	471	250	506
10	474	300	508
20	477	350	510
30	480	400	511
40	482	450	512
50	485	500	513
60	487	550	514
70	488	600	514
80	490	650	515
90	492	700	515
100	493	750	515
110	494	800	516
120	496	850	516
130	497	900	516
140	498	950	516
150	499	1000	517
200	503	1100	517

At a temperature close to absolute zero, chlorine is in a solid state and has a low specific heat capacity (19 J/(kg·K)). As the temperature of solid Cl 2 increases, its heat capacity increases and reaches 720 J/(kg K) at minus 143°C.

Liquid chlorine has a specific heat capacity of 918 ... 949 J / (kg K) in the range from 0 to -90 degrees Celsius. According to the table, it can be seen that the specific heat of liquid chlorine is higher than that of gaseous chlorine and decreases with increasing temperature.

Thermal conductivity of chlorine

The table shows the values ​​of the thermal conductivity coefficients of gaseous chlorine at normal atmospheric pressure in the temperature range from -70 to 400°C.

The thermal conductivity coefficient of chlorine under normal conditions is 0.0079 W / (m deg), which is 3 times less than at the same temperature and pressure. Heating chlorine leads to an increase in its thermal conductivity. Thus, at a temperature of 100°C, the value of this physical property of chlorine increases to 0.0114 W/(m deg).

Thermal conductivity of chlorine gas

t, °С	λ, W/(m deg)	t, °С	λ, W/(m deg)
-70	0,0054	50	0,0096
-60	0,0058	60	0,01
-50	0,0062	70	0,0104
-40	0,0065	80	0,0107
-30	0,0068	90	0,0111
-20	0,0072	100	0,0114
-10	0,0076	150	0,0133
0	0,0079	200	0,0149
10	0,0082	250	0,0165
20	0,0086	300	0,018
30	0,009	350	0,0195
40	0,0093	400	0,0207

Viscosity of chlorine

The coefficient of dynamic viscosity of gaseous chlorine in the temperature range of 20...500°C can be approximately calculated by the formula:

where η T is the coefficient of dynamic viscosity of chlorine at a given temperature T, K;
η T 0 is the coefficient of dynamic viscosity of chlorine at a temperature T 0 =273 K (at n.a.);
C is Sutherland's constant (for chlorine C=351).

Under normal conditions, the dynamic viscosity of chlorine is 0.0123·10 -3 Pa·s. When heated, such a physical property of chlorine as viscosity takes on higher values.

Liquid chlorine has an order of magnitude higher viscosity than gaseous chlorine. For example, at a temperature of 20°C, the dynamic viscosity of liquid chlorine has a value of 0.345·10 -3 Pa·s and decreases with increasing temperature.

Sources:

1. Barkov S. A. Halogens and a subgroup of manganese. Elements of group VII of the periodic system of D. I. Mendeleev. Student aid. M .: Education, 1976 - 112 p.
2. Tables of physical quantities. Directory. Ed. acad. I. K. Kikoina. Moscow: Atomizdat, 1976 - 1008 p.
3. Yakimenko L. M., Pasmanik M. I. Reference book on the production of chlorine, caustic soda and basic chlorine products. Ed. 2nd, trans. etc. M.: Chemistry, 1976 - 440 p.

Cl 2 at vol. T - yellow-green gas with a sharp suffocating odor, heavier than air - 2.5 times, slightly soluble in water (~ 6.5 g / l); X. R. in nonpolar organic solvents. It is found free only in volcanic gases.

How to get

Based on the process of oxidation of anions Cl -

2Cl - - 2e - = Cl 2 0

Industrial

Electrolysis of aqueous solutions of chlorides, more often - NaCl:

2NaCl + 2H 2 O \u003d Cl 2 + 2NaOH + H 2

Laboratory

Oxidation conc. HCI various oxidizing agents:

4HCI + MnO 2 \u003d Cl 2 + MpCl 2 + 2H 2 O

16HCl + 2KMnO 4 \u003d 5Cl 2 + 2MnCl 2 + 2KCl + 8H 2 O

6HCl + KClO 3 \u003d ZCl 2 + KCl + 3H 2 O

14HCl + K 2 Cr 2 O 7 \u003d 3Cl 2 + 2CrCl 3 + 2KCl + 7H 2 O

Chemical properties

Chlorine is a very strong oxidizing agent. Oxidizes metals, non-metals and complex substances, while turning into very stable anions Cl -:

Cl 2 0 + 2e - \u003d 2Cl -

Reactions with metals

Active metals in an atmosphere of dry chlorine gas ignite and burn; in this case, metal chlorides are formed.

Cl 2 + 2Na = 2NaCl

3Cl 2 + 2Fe = 2FeCl 3

Inactive metals are more easily oxidized by wet chlorine or its aqueous solutions:

Cl 2 + Cu \u003d CuCl 2

3Cl 2 + 2Au = 2AuCl 3

Reactions with non-metals

Chlorine does not directly interact only with O 2, N 2, C. Reactions proceed with other non-metals under various conditions.

Non-metal halides are formed. The most important is the reaction of interaction with hydrogen.

Cl 2 + H 2 \u003d 2HC1

Cl 2 + 2S (melt) = S 2 Cl 2

ЗCl 2 + 2Р = 2РCl 3 (or РCl 5 - in excess of Cl 2)

2Cl 2 + Si = SiCl 4

3Cl 2 + I 2 \u003d 2ICl 3

Displacement of free non-metals (Br 2, I 2, N 2, S) from their compounds

Cl 2 + 2KBr = Br 2 + 2KCl

Cl 2 + 2KI \u003d I 2 + 2KCl

Cl 2 + 2HI \u003d I 2 + 2HCl

Cl 2 + H 2 S \u003d S + 2HCl

ZCl 2 + 2NH 3 \u003d N 2 + 6HCl

Disproportionation of chlorine in water and aqueous solutions of alkalis

As a result of self-oxidation-self-healing, some chlorine atoms are converted into Cl - anions, while others in a positive oxidation state are part of the ClO - or ClO 3 - anions.

Cl 2 + H 2 O \u003d HCl + HClO hypochlorous to-ta

Cl 2 + 2KOH \u003d KCl + KClO + H 2 O

3Cl 2 + 6KOH = 5KCl + KClO 3 + 3H 2 O

3Cl 2 + 2Ca (OH) 2 \u003d CaCl 2 + Ca (ClO) 2 + 2H 2 O

These reactions are important because they lead to the production of oxygen compounds of chlorine:

KClO 3 and Ca (ClO) 2 - hypochlorites; KClO 3 - potassium chlorate (bertolet salt).

Interaction of chlorine with organic substances

a) substitution of hydrogen atoms in OB molecules

b) attachment of Cl 2 molecules at the point of breaking of multiple carbon-carbon bonds

H 2 C \u003d CH 2 + Cl 2 → ClH 2 C-CH 2 Cl 1,2-dichloroethane

HC≡CH + 2Cl 2 → Cl 2 HC-CHCl 2 1,1,2,2-tetrachloroethane

Hydrogen chloride and hydrochloric acid

Hydrogen chloride gas

Physical and chemical properties

HCl is hydrogen chloride. At rev. T - colorless. gas with a pungent odor, liquefies quite easily (mp. -114°С, bp. -85°С). Anhydrous HCl, both in gaseous and liquid states, is non-conductive, chemically inert with respect to metals, metal oxides and hydroxides, and also to many other substances. This means that in the absence of water, hydrogen chloride does not exhibit acidic properties. Only at very high temperatures does gaseous HCl react with metals, even such inactive ones as Cu and Ag.
The reducing properties of the chloride anion in HCl also manifest themselves to a small extent: it is oxidized by fluorine at vol. T, and also at high T (600°C) in the presence of catalysts, it reversibly reacts with oxygen:

2HCl + F 2 \u003d Cl 2 + 2HF

4HCl + O 2 \u003d 2Cl 2 + 2H 2 O

Gaseous HCl is widely used in organic synthesis (hydrochlorination reactions).

How to get

1. Synthesis from simple substances:

H 2 + Cl 2 \u003d 2HCl

2. Formed as a by-product during hydrocarbon chlorination:

R-H + Cl 2 = R-Cl + HCl

3. In the laboratory, they receive the action of conc. H 2 SO 4 for chlorides:

H 2 SO 4 (conc.) + NaCl \u003d 2HCl + NaHSO 4 (with low heating)

H 2 SO 4 (conc.) + 2NaCl \u003d 2HCl + Na 2 SO 4 (with very strong heating)

An aqueous solution of HCl is a strong acid (hydrochloric, or hydrochloric)

HCl is very soluble in water: at vol. T in 1 l of H 2 O dissolves ~ 450 l of gas (dissolution is accompanied by the release of a significant amount of heat). A saturated solution has a mass fraction of HCl equal to 36-37%. This solution has a very pungent, suffocating odor.

HCl molecules in water almost completely decompose into ions, i.e., an aqueous solution of HCl is a strong acid.

Chemical properties of hydrochloric acid

1. HCl dissolved in water exhibits all the general properties of acids due to the presence of H + ions

HCl → H + + Cl -

Interaction:

a) with metals (up to H):

2HCl 2 + Zn \u003d ZnCl 2 + H 2

b) with basic and amphoteric oxides:

2HCl + CuO \u003d CuCl 2 + H 2 O

6HCl + Al 2 O 3 \u003d 2AlCl 3 + ZN 2 O

c) with bases and amphoteric hydroxides:

2HCl + Ca (OH) 2 \u003d CaCl 2 + 2H 2 O

3HCl + Al(OH) 3 \u003d AlCl 3 + ZN 2 O

d) with salts of weaker acids:

2HCl + CaCO 3 \u003d CaCl 2 + CO 2 + H 3 O

HCl + C 6 H 5 ONa \u003d C 6 H 5 OH + NaCl

e) with ammonia:

HCl + NH 3 \u003d NH 4 Cl

Reactions with strong oxidizing agents F 2 , MnO 2 , KMnO 4 , KClO 3 , K 2 Cr 2 O 7 . Anion Cl - is oxidized to free halogen:

2Cl - - 2e - = Cl 2 0

For reaction equations, see "Getting Chlorine". OVR between hydrochloric and nitric acids is of particular importance:

Reactions with organic compounds

Interaction:

a) with amines (as organic bases)

R-NH 2 + HCl → + Cl -

b) with amino acids (as amphoteric compounds)

Oxides and oxoacids of chlorine

Acid oxides

acids

salt

Chemical properties

1. All oxoacids of chlorine and their salts are strong oxidizers.

2. Almost all compounds decompose when heated due to intramolecular oxidation-reduction or disproportionation.

Bleaching powder

Chlorine (whitewash) lime - a mixture of hypochlorite and calcium chloride, has a bleaching and disinfecting effect. Sometimes it is considered as an example of a mixed salt, which simultaneously contains anions of two acids:

Javel water

Aqueous solution of chloride and potassium hapochlorite KCl + KClO + H 2 O