Cl2 color. Physical properties of chlorine: density, heat capacity, thermal conductivity of Cl2

No matter how negatively we feel about public restrooms, nature dictates its own rules, and you have to visit them. In addition to natural (for this place) odors, another familiar aroma is bleach used to disinfect the room. It got its name because of the main active ingredient in it - Cl. Let's learn about this chemical element and its properties, and also give a description of chlorine by position in the periodic system.

How this item was discovered

For the first time a chlorine-containing compound (HCl) was synthesized in 1772 by the British priest Joseph Priestley.

After 2 years, his Swedish colleague Karl Scheele managed to describe a method for separating Cl using the reaction between hydrochloric acid and manganese dioxide. However, this chemist did not understand that a new chemical element was being synthesized as a result.

It took scientists almost 40 years to learn how to extract chlorine in practice. This was first done by the British Humphrey Davy in 1811. In doing so, he used a different reaction than his theoretic predecessors. Davy broke down NaCl (known to most as table salt) by electrolysis.

After studying the resulting substance, the British chemist realized that it was elemental. After this discovery, Davy not only named it - chlorine (chlorine), but was also able to characterize chlorine, although it was very primitive.

Chlorine turned into chlorine (chlore) thanks to Joseph Gay-Lussac and exists in this form in French, German, Russian, Belarusian, Ukrainian, Czech, Bulgarian and some other languages ​​today. In English to this day, the name "chlorin" is used, and in Italian and Spanish "chloro".

The element under consideration was described in more detail by Jens Berzelius in 1826. It was he who was able to determine its atomic mass.

What is chlorine (Cl)

Having considered the history of the discovery of this chemical element, it is worth learning more about it.

The name chlorine was derived from the Greek word χλωρός ("green"). It was given because of the yellowish-greenish color of this substance.

Chlorine exists on its own as a diatomic gas Cl 2, but in this form it practically does not occur in nature. More often it appears in various compounds.

In addition to the distinctive shade, chlorine is characterized by a sweetish-pungent odor. It is a very toxic substance, therefore, if it enters the air and is inhaled by a person or animal, it can lead to their death within a few minutes (depending on the concentration of Cl).

Since chlorine is almost 2.5 times heavier than air, it will always be below it, that is, near the ground itself. For this reason, if you suspect the presence of Cl, you should climb as high as possible, since there will be a lower concentration of this gas.

Also, unlike some other toxic substances, chlorine-containing ones have a characteristic color, which can allow them to be visually identified and acted upon. Most standard gas masks help protect the respiratory organs and mucous membranes from Cl damage. However, for complete safety, more serious measures must be taken, up to the neutralization of the toxic substance.

It is worth noting that it was with the use of chlorine as a poisonous gas by the Germans in 1915 that chemical weapons began their history. As a result of the use of almost 200 tons of the substance, 15 thousand people were poisoned in a few minutes. A third of them died almost instantly, a third received permanent damage, and only 5 thousand managed to escape.

Why is such a dangerous substance still not banned and millions of tons are mined annually? It's all about its special properties, and to understand them, it is worth considering the characteristics of chlorine. The easiest way to do this is with the periodic table.

Characterization of chlorine in the periodic system

Chlorine as halogen

In addition to extreme toxicity and a pungent odor (characteristic of all representatives of this group), Cl is highly soluble in water. A practical confirmation of this is the addition of chlorine-containing detergents to pool water.

Upon contact with moist air, the substance in question begins to smoke.

Properties of Cl as a non-metal

Considering the chemical characteristics of chlorine, it is worth paying attention to its non-metallic properties.

It has the ability to form compounds with almost all metals and non-metals. An example is the reaction with iron atoms: 2Fe + 3Cl 2 → 2FeCl 3.

It is often necessary to use catalysts to carry out reactions. This role can be played by H 2 O.

Often, reactions with Cl are endothermic (they absorb heat).

It should be noted that in crystalline form (in powder form), chlorine interacts with metals only when heated to high temperatures.

Reacting with other non-metals (except O 2, N, F, C and inert gases), Cl forms compounds - chlorides.

When reacting with O 2, oxides are formed that are extremely unstable and prone to decay. In them, the oxidation state of Cl can manifest itself from +1 to +7.

When interacting with F, fluorides are formed. Their degree of oxidation can be different.

Chlorine: a characteristic of a substance in terms of its physical properties

In addition to chemical properties, the element under consideration also has physical properties.

Effect of temperature on the aggregate state of Cl

Having considered the physical characteristics of the chlorine element, we understand that it is able to go into different states of aggregation. It all depends on the temperature regime.

In its normal state, Cl is a highly corrosive gas. However, he can easily liquefy. This is affected by temperature and pressure. For example, if it is equal to 8 atmospheres, and the temperature is +20 degrees Celsius, Cl 2 is an acid yellow liquid. It is able to maintain this state of aggregation up to +143 degrees, if the pressure also continues to rise.

Upon reaching -32 ° C, the state of chlorine ceases to depend on pressure, and it continues to remain liquid.

Crystallization of a substance (solid state) occurs at -101 degrees.

Where in nature exists Cl

Having considered general characteristics chlorine, it is worth finding out where such a difficult element can be found in nature.

Due to its high reactivity, it is almost never found in its pure form (therefore, at the beginning of the study of this element, scientists took years to learn how to synthesize it). Usually Cl is found in compounds in various minerals: halite, sylvin, kainite, bischofite, etc.

Most of all, it is found in salts extracted from sea or ocean water.

Effect on the body

When considering the characteristics of chlorine, it has already been said more than once that it is extremely poisonous. At the same time, atoms of matter are contained not only in minerals, but also in almost all organisms, from plants to humans.

Due to their special properties, Cl ions penetrate cell membranes better than others (therefore, more than 80% of all chlorine in the human body is located in the intercellular space).

Together with K, Cl is responsible for the regulation of the water-salt balance and, as a result, for osmotic equality.

Despite such an important role in the body, pure Cl 2 kills all living things - from cells to entire organisms. However, in controlled doses and with short-term exposure, it does not have time to cause damage.

A vivid example of the last statement is any pool. As you know, water in such institutions is disinfected with Cl. At the same time, if a person rarely visits such an institution (once a week or a month), it is unlikely that he will suffer from the presence of this substance in the water. However, employees of such institutions, especially those who stay in the water almost all day (rescuers, instructors) often suffer from skin diseases or have a weakened immune system.

In connection with all this, after visiting the pools, it is imperative to take a shower - to wash off possible chlorine residues from the skin and hair.

Human use of Cl

Keeping in mind from the characterization of chlorine that it is a "capricious" element (when it comes to interacting with other substances), it will be interesting to know that it is quite often used in industry.

First of all, it is used to disinfect many substances.

Cl is also used in the manufacture of certain types of pesticides, which helps save crops from pests.

The ability of this substance to interact with almost all elements of the periodic table (a characteristic of chlorine as a non-metal) helps to extract certain types of metals (Ti, Ta and Nb), as well as lime and hydrochloric acid with its help.

In addition to all of the above, Cl is used in the production of industrial substances (polyvinyl chloride) and medical preparations(chlorhexidine).

It is worth mentioning that today a more effective and safe disinfectant has been found - ozone (O 3 ). However, its production is more expensive than chlorine, and this gas is even more unstable than chlorine ( a brief description of physical properties in 6-7 p.). Therefore, few can afford to use ozonation instead of chlorination.

How is chlorine produced?

Today, many methods are known for the synthesis of this substance. All of them fall into two categories:

• Chemical.
• Electrochemical.

In the first case, Cl is obtained as a result of a chemical reaction. However, in practice they are very costly and inefficient.

Therefore, electrochemical methods (electrolysis) are preferred in industry. There are three of them: diaphragm, membrane and mercury electrolysis.

Chlorine (χλωρός - green) - an element of the main subgroup of the seventh group, the third period of the periodic system chemical elements D. I. Mendeleev, with atomic number 17. 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. IN earth's crust chlorine is the most common halogen. 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.

Chlorine accounts for 0.025% of the total number of atoms in the earth's crust, the Clarke number of chlorine is 0.19%, and the human body contains 0.25% of 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%.

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

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

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

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

Reactions with organic substances

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 industrial way obtaining 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

Produced chlorine is stored in special "tanks" or pumped into steel cylinders high pressure. 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, from which they are made: insulation for wires, window profile, packaging materials, clothing and footwear, linoleum and gramophone records, varnishes, equipment and foam plastics, toys, instrument parts, Construction 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 practical use found 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 disinfection 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 service life of pipelines based on polyolefins: polyethylene pipes of various types, including cross-linked polyethylene, 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 metabolism 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. An excessive concentration of chlorine ions in plants can also have a negative side, for example, reduce the content of chlorophyll, reduce the activity of photosynthesis, retard the growth and development of Baskunchak chlorine plants). 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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Chlorine(lat. Chlorum), Cl, a chemical element of Group VII of the Mendeleev periodic system, atomic number 17, atomic mass 35.453; belongs to the halogen family. Under normal conditions (0°C, 0.1 MN/m 2 , or 1 kgf/cm 2) a yellow-green gas with a sharp irritating odor. Natural Chlorine consists of two stable isotopes: 35 Cl (75.77%) and 37 Cl (24.23%). Artificially obtained radioactive isotopes with mass numbers 31-47, in particular: 32, 33, 34, 36, 38, 39, 40 with half-lives (T ½) respectively 0.31; 2.5; 1.56 sec; 3.1 10 5 years; 37.3, 55.5 and 1.4 min. 36 Cl and 38 Cl are used as tracers.

Historical reference. Chlorine was obtained for the first time in 1774 by K. Scheele by the interaction of hydrochloric acid with pyrolusite MnO 2 . However, only in 1810, G. Davy established that chlorine is an element and named it chlorine (from the Greek chloros - yellow-green). In 1813, J. L. Gay-Lussac proposed the name Chlorine for this element.

Distribution of chlorine in nature. Chlorine occurs in nature only in the form of compounds. The average content of Chlorine in the earth's crust (clarke) is 1.7·10 -2% by mass, in acid igneous rocks - granites and others 2.4·10 -2, in basic and ultrabasic 5·10 -3 . Water migration plays a major role in the history of chlorine in the earth's crust. In the form of Cl ion - it is found in the World Ocean (1.93%), underground brines and salt lakes. The number of own minerals (mainly natural chlorides) is 97, the main one being halite NaCl (Rock salt). Large deposits of potassium and magnesium chlorides and mixed chlorides are also known: sylvin KCl, sylvinite (Na,K)Cl, carnalite KCl MgCl 2 6H 2 O, kainite KCl MgSO 4 3H 2 O, bischofite MgCl 2 6H 2 O .In the history of the Earth great importance HCl contained in volcanic gases entered the upper parts of the earth's crust.

Physical properties of chlorine. Chlorine has t bp -34.05°C, t pl -101°C. The density of gaseous chlorine under normal conditions is 3.214 g/l; saturated steam at 0°C 12.21 g/l; liquid chlorine at a boiling point of 1.557 g/cm 3 ; solid chlorine at - 102°C 1.9 g/cm 3 . Saturated vapor pressure of Chlorine at 0°C 0.369; at 25°C 0.772; at 100°C 3.814 MN/m 2 or 3.69 respectively; 7.72; 38.14 kgf / cm 2. Heat of fusion 90.3 kJ/kg (21.5 cal/g); heat of vaporization 288 kJ/kg (68.8 cal/g); heat capacity of gas at constant pressure 0.48 kJ/(kg K) . Critical constants of Chlorine: temperature 144°C, pressure 7.72 MN/m2 (77.2 kgf/cm2), density 573 g/l, specific volume 1.745·10 -3 l/g. Solubility (in g / l) Chlorine at a partial pressure of 0.1 MN / m 2, or 1 kgf / cm 2, in water 14.8 (0 ° C), 5.8 (30 ° C), 2.8 ( 70°C); in a solution of 300 g/l NaCl 1.42 (30°C), 0.64 (70°C). Below 9.6°C in aqueous solutions, chlorine hydrates of variable composition Cl 2 ·nH 2 O are formed (where n = 6-8); These are yellow crystals of cubic syngony, decomposing when the temperature rises into Chlorine and water. Chlorine dissolves well in TiCl 4 , SiCl 4 , SnCl 4 and some organic solvents (especially in hexane C 6 H 14 and carbon tetrachloride CCl 4). The chlorine molecule is diatomic (Cl 2). The degree of thermal dissociation of Cl 2 + 243 kJ \u003d 2Cl at 1000 K is 2.07 10 -4%, at 2500 K 0.909%.

Chemical properties of chlorine. External electronic configuration of the atom Cl 3s 2 Зр 5 . In accordance with this, chlorine in compounds exhibits oxidation states -1, +1, +3, +4, +5, +6 and +7. The covalent radius of the atom is 0.99Å, the ionic radius of Cl is 1.82Å, the electron affinity of the Chlorine atom is 3.65 eV, and the ionization energy is 12.97 eV.

Chemically, chlorine is very active, it combines directly with almost all metals (with some only in the presence of moisture or when heated) and with non-metals (except carbon, nitrogen, oxygen, inert gases), forming the corresponding chlorides, reacts with many compounds, replaces hydrogen in saturated hydrocarbons and joins unsaturated compounds. Chlorine displaces bromine and iodine from their compounds with hydrogen and metals; from the compounds of chlorine with these elements, it is displaced by fluorine. Alkali metals in the presence of traces of moisture interact with chlorine with ignition, most metals react with dry chlorine only when heated. Steel, as well as some metals, is resistant to dry chlorine at low temperatures, so they are used for the manufacture of equipment and storage facilities for dry chlorine. Phosphorus ignites in an atmosphere of chlorine, forming РCl 3 , and upon further chlorination - РCl 5 ; sulfur with Chlorine, when heated, gives S 2 Cl 2, SCl 2 and other S n Cl m. Arsenic, antimony, bismuth, strontium, tellurium interact vigorously with chlorine. A mixture of chlorine and hydrogen burns with a colorless or yellow-green flame to form hydrogen chloride (this is a chain reaction).

The maximum temperature of the hydrogen-chlorine flame is 2200°C. Mixtures of chlorine with hydrogen containing from 5.8 to 88.5% H 2 are explosive.

Chlorine forms oxides with oxygen: Cl 2 O, ClO 2 , Cl 2 O 6 , Cl 2 O 7 , Cl 2 O 8 , as well as hypochlorites (salts of hypochlorous acid), chlorites, chlorates and perchlorates. All oxygen compounds of chlorine form explosive mixtures with easily oxidized substances. Chlorine oxides are unstable and can explode spontaneously, hypochlorites decompose slowly during storage, chlorates and perchlorates can explode under the influence of initiators.

Chlorine in water is hydrolyzed, forming hypochlorous and hydrochloric acids: Cl 2 + H 2 O \u003d HClO + HCl. When chlorinating aqueous solutions of alkalis in the cold, hypochlorites and chlorides are formed: 2NaOH + Cl 2 \u003d NaClO + NaCl + H 2 O, and when heated - chlorates. By chlorination of dry calcium hydroxide, bleach is obtained.

When ammonia reacts with chlorine, nitrogen trichloride is formed. In the chlorination of organic compounds, chlorine either replaces hydrogen or adds via multiple bonds, forming various chlorine-containing organic compounds.

Chlorine forms interhalogen compounds with other halogens. Fluorides ClF, ClF 3 , ClF 3 are very reactive; for example, in an atmosphere of ClF 3 glass wool ignites spontaneously. Chlorine compounds with oxygen and fluorine are known - Chlorine oxyfluorides: ClO 3 F, ClO 2 F 3 , ClOF, ClOF 3 and fluorine perchlorate FClO 4 .

Getting Chlorine. Chlorine began to be produced in industry in 1785 by the interaction of hydrochloric acid with manganese (II) oxide or pyrolusite. In 1867, the English chemist G. Deacon developed a method for producing chlorine by oxidizing HCl with atmospheric oxygen in the presence of a catalyst. Since the late 19th - early 20th century, chlorine has been produced by electrolysis of aqueous solutions of alkali metal chlorides. These methods produce 90-95% of Chlorine in the world. Small amounts of chlorine are obtained incidentally in the production of magnesium, calcium, sodium, and lithium by electrolysis of molten chlorides. Two main methods of electrolysis of NaCl aqueous solutions are used: 1) in electrolyzers with a solid cathode and a porous filter diaphragm; 2) in electrolyzers with a mercury cathode. According to both methods, gaseous chlorine is released on a graphite or oxide titanium-ruthenium anode. According to the first method, hydrogen is released at the cathode and a solution of NaOH and NaCl is formed, from which commercial caustic soda is isolated by subsequent processing. According to the second method, sodium amalgam is formed on the cathode, when it decomposes clean water in a separate apparatus, a NaOH solution, hydrogen and pure mercury are obtained, which again goes into production. Both methods give 1.125 tons of NaOH per 1 ton of Chlorine.

Diaphragm electrolysis requires less capital investment for chlorine production and produces cheaper NaOH. The mercury cathode method produces very pure NaOH, but the loss of mercury pollutes the environment.

The use of chlorine. One of the important branches of the chemical industry is the chlorine industry. The main quantities of chlorine are processed at the place of its production into chlorine-containing compounds. Chlorine is stored and transported in liquid form in cylinders, barrels, railway tanks or in specially equipped vessels. For industrial countries, the following approximate consumption of chlorine is typical: for the production of chlorine-containing organic compounds - 60-75%; inorganic compounds containing Chlorine, -10-20%; for bleaching of pulp and fabrics - 5-15%; for sanitary needs and water chlorination - 2-6% of the total output.

Chlorine is also used for the chlorination of some ores in order to extract titanium, niobium, zirconium and others.

Chlorine in the body Chlorine is one of the biogenic elements, a constant component of plant and animal tissues. The content of chlorine in plants (a lot of chlorine in halophytes) - from thousandths of a percent to whole percent, in animals - tenths and hundredths of a percent. daily requirement an adult in Chlorine (2-4 g) is covered by food. With food, Chlorine is usually supplied in excess in the form of sodium chloride and potassium chloride. Bread, meat and dairy products are especially rich in Chlorine. In animals, chlorine is the main osmotically active substance in blood plasma, lymph, cerebrospinal fluid, and some tissues. Plays a role in water-salt metabolism, contributing to the retention of water by tissues. Regulation of acid-base balance in tissues is carried out along with other processes by changing the distribution of Chlorine between the blood and other tissues. Chlorine is involved in energy metabolism in plants, activating both oxidative phosphorylation and photophosphorylation. Chlorine has a positive effect on the absorption of oxygen by the roots. Chlorine is necessary for the production of oxygen during photosynthesis by isolated chloroplasts. Chlorine is not included in most nutrient media for artificial cultivation of plants. It is possible that very low concentrations of Chlorine are sufficient for the development of plants.

Chlorine poisoning is possible in the chemical, pulp and paper, textile, pharmaceutical industries and others. Chlorine irritates the mucous membranes of the eyes and respiratory tract. Secondary infection usually joins the primary inflammatory changes. Acute poisoning develops almost immediately. Inhalation of medium and low concentrations of chlorine causes tightness and pain in the chest, dry cough, rapid breathing, pain in the eyes, lacrimation, increased levels of leukocytes in the blood, body temperature, etc. Possible bronchopneumonia, toxic pulmonary edema, depression, convulsions . In mild cases, recovery occurs in 3-7 days. As long-term consequences, catarrhs ​​of the upper respiratory tract, recurrent bronchitis, pneumosclerosis and others are observed; possible activation of pulmonary tuberculosis. With prolonged inhalation of small concentrations of Chlorine, similar, but slowly developing forms of the disease are observed. Prevention of poisoning: sealing of production facilities, equipment, effective ventilation, if necessary, the use of a gas mask. The production of chlorine, bleach and other chlorine-containing compounds belongs to industries with harmful working conditions.

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. Crécy (in the Battle of Crécy in 1346, 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 middle of the Libyan desert was famous temple 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 Davy, who in 1807 decomposed electric shock table salt to 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 sharp 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 a temperature of -34.05 ° C, chlorine condenses into a yellow liquid (density 1.56 g / cm hardens at a temperature of -101.6°C. At elevated pressure, chlorine can be turned into a liquid and at more high 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. It is then cooled down first. cold water in tall towers lined from the inside ceramic tiles and filled with a ceramic nozzle (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 of the 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, when chlorinating acetic acid, first one hydrogen of the methyl group is replaced by chlorine, then another, then 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. IN German magazine"Annalen der Chemie und Pharmacie" appeared a mocking letter from the famous German chemist Friedrich Wöhler under the pseudonym S.C.H. 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.

DEFINITION

Chlorine- a chemical element of group VII of the 3rd period Periodic system chemical elements D.I. Mendeleev. Non-metal.

Refers to elements - p -family. Halogen. The serial number is 17. The structure of the external electronic level is 3s 2 3 p 5. Relative atomic mass - 35.5 a.m.u. The chlorine molecule is diatomic - Cl 2.

Chemical properties of chlorine

Chlorine reacts with simple metals:

Cl 2 + 2Sb = 2SbCl 3 (t);

Cl 2 + 2Fe \u003d 2FeCl 3;

Cl 2 + 2Na = 2NaCl.

Chlorine interacts with simple non-metal substances. So, when interacting with phosphorus and sulfur, the corresponding chlorides are formed, with fluorine - fluorides, with hydrogen - hydrogen chloride, with oxygen - oxides, etc.:

5Cl 2 + 2P = 2HCl 5 ;

Cl 2 + 2S \u003d SCl 2;

Cl 2 + H 2 \u003d 2HCl;

Cl 2 + F 2 \u003d 2ClF.

Chlorine is able to displace bromine and iodine from their compounds with hydrogen and metals:

Cl 2 + 2HBr = Br 2 + 2HCl;

Cl 2 + 2NaI \u003d I 2 + 2NaCl.

Chlorine is able to dissolve in water and alkalis, while chlorine disproportionation reactions occur, and the composition of the reaction products depends on the conditions for its implementation:

Cl 2 + H 2 O ↔ HCl + HClO;

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

3Cl 2 + 6NaOH \u003d 5NaCl + NaClO 3 + 3H 2 O.

Chlorine interacts with a non-salt-forming oxide - CO to form a substance with a trivial name - phosgene, with ammonia to form ammonium trichloride:

Cl 2 + CO \u003d COCl 2;

3 Cl 2 + 4NH 3 \u003d NCl 3 + 3NH 4 Cl.

In reactions, chlorine exhibits the properties of an oxidizing agent:

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

Chlorine enters into reactions of interaction with organic substances of the class of alkanes, alkenes and arenes:

CH 3 -CH 3 + Cl 2 = CH 3 -CH 2 -Cl + HCl (condition - UV radiation);

CH 2 \u003d CH 2 + Cl 2 \u003d CH 2 (Cl) -CH 2 -Cl;

C 6 H 6 + Cl 2 \u003d C 6 H 5 -Cl + HCl (kat \u003d FeCl 3, AlCl 3);

C 6 H 6 + 6Cl 2 \u003d C 6 H 6 Cl 6 + 6HCl (condition - UV radiation).

Physical properties of chlorine

Chlorine is a yellow-green gas. Thermally stable. When chilled water is saturated with chlorine, a solid clarate is formed. It dissolves well in water, undergoes dismutation to a large extent ("chlorine water"). Dissolves in carbon tetrachloride, liquid SiCl 4 and TiCl 4 . It is poorly soluble in saturated sodium chloride solution. Does not react with oxygen. Strong oxidizer. Boiling point - -34.1C, melting point - -101.03C.

Getting chlorine

Previously, chlorine was obtained by the Scheele method (reaction of manganese (VI) oxide with hydrochloric acid) or by the Deacon method (reaction of interaction of hydrogen chloride with oxygen):

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

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

In our time, the following reactions are used to obtain chlorine:

NaOCl + 2HCl = NaCl + Cl 2 + H 2 O;

2KMnO 4 + 16HCl = 2KCl + 2MnCl 2 +5 Cl 2 + 8H 2 O;

2NaCl + 2H 2 O \u003d 2NaOH + Cl 2 + H 2 (condition - electrolysis).

Application of chlorine

Chlorine has found wide application in various fields of industry, as it is used in the production of polymeric materials (polyvinyl chloride), bleaches, organochlorine insecticides (hexachloran), chemical warfare agents (phosgene), for water disinfection, in the food industry, in metallurgy, etc.

Examples of problem solving

EXAMPLE 1

EXAMPLE 2