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Chemical composition of hydrochloric acid. Hydrochloric acid

1.2679; G crit 51.4°C, p crit 8.258 MPa, d crit 0.42 g/cm 3 ; -92.31 kJ/, DH pl 1.9924 kJ/ (-114.22°C), DH isp 16.1421 kJ/ (-8.05°C); 186.79 J/(mol K); (Pa): 133.32 10 -6 (-200.7 °C), 2.775 10 3 (-130.15 °C), 10.0 10 4 (-85.1 °C), 74, 0 10 4 (-40°C), 24.95 10 5 (O °C), 76.9 10 5 (50 °C); level of temperature dependence logp(kPa) = -905.53/T+ 1.75lgT- -500.77·10 -5 T+3.78229 (160-260 K); coefficient 0.00787; g 23 mN/cm (-155°C); r 0.29 10 7 Ohm m (-85°C), 0.59 10 7 (-114.22°C). See also table. 1.


R-value of HC1 at 25 °C and 0.1 MPa (mol %): in pentane - 0.47, hexane - 1.12, heptane - 1.47, octane - 1.63. The P-rhythm of HC1 in alkyl and aryl halides is low, for example. 0.07 / for C 4 H 9 C1. The pH value in the range from -20 to 60° C decreases in the series dichloroethane-tri-chloroethane-tetrachloroethane-trichlorethylene. The pH value at 10°C in a series is approximately 1/, in carbon ethers it is 0.6/, in carbonic compounds it is 0.2/. Stable R 2 O · HCl are formed. The P-rhythm of HC1 in obeys and is for KCl 2.51·10 -4 (800°С), 1.75·10 -4 / (900°С), for NaCl 1.90·10 -4 / (900° WITH).

Salt room. HCl in water is highly exothermic. process, for endless dilution. aqueous solution D H 0 HCl -69.9 kJ/, Cl -- 167.080 kJ/; HC1 is completely ionized. The pH value of HC1 depends on the temperature (Table 2) and the partial HC1 in the gas mixture. Density of salt decomposition. and h at 20 °C are presented in table. 3 and 4. With increasing temperature, h hydrochloric acid decreases, for example: for 23.05% hydrochloric acid at 25 ° C h 1364 mPa s, at 35 ° C 1.170 mPa s hydrochloric acid containing h per 1 HC1, is [kJ/(kg K)]: 3.136 (n = 10), 3.580 (n = 20), 3.902 (n = 50), 4.036 (n = 100), 4.061 (n = 200).






HCl forms c (Table 5). In the HCl-water system there are three eutectics. points: - 74.7 °C (23.0% by weight HCl); -73.0°C (26.5% HCl); -87.5°C (24.8% HC1, metastable phase). Known HCl nH 2 O, where n = 8. 6 (mp. -40 ° C), 4. 3 (mp. -24.4 ° C), 2 (mp. -17.7 °C) and 1 (mp -15.35°C). crystallizes from 10% hydrochloric acid at -20, from 15% at -30, from 20% at -60 and from 24% at -80°C. The P-value of halides decreases with increasing HCl in hydrochloric acid, which is used for their.

Chemical properties. Pure dry HCl begins to dissociate above 1500°C and is chemically passive. Mn. , C, S, P do not interact. even with liquid HCl. C, reacts above 650 °C, with Si, Ge and B-c present. AlCl 3, with transition metals - at 300 °C and above. It is oxidized by O 2 and HNO 3 to Cl 2, with SO 3 it gives C1SO 3 H. About the solutions with org. connections see .

WITH Olina is chemically very active. Dissolves with the release of H 2 everything that has a negative. ,with me. and forms, releases free. who are you from people like , etc.

Receipt. In the HCl industry, the following is obtained. methods - sulfate, synthetic. and from exhaust gases (by-products) of a number of processes. The first two methods lose their meaning. Thus, in the USA in 1965 the share of waste hydrochloric acid was 77.6% of the total production volume, and in 1982 - 94%.

The production of hydrochloric acid (reactive, obtained by the sulfate method, synthetic, waste gas) is to obtain HCl from the last. his . Depending on the method of heat removal (reaches 72.8 kJ/), processes are divided into isothermal, adiabatic. and combined.

The sulfate method is based on interaction. NaCl with conc. H 2 SO 4 at 500-550 ° C. Reaction contain from 50-65% HCl (muffle) to 5% HCl (reactor with). It is proposed to replace H 2 SO 4 with a mixture of SO 2 and O 2 (process temperature approx. 540 °C, cat. Fe 2 O 3).

The direct synthesis of HCl is based on a chain reaction: H 2 + Cl 2 2HCl + 184.7 kJ K p is calculated by the equation: logK p = 9554/T- 0.5331g T+ 2.42.

The reaction is initiated by light, moisture, solid porous (, porous Pt) and certain minerals. in-you ( , ). Synthesis is carried out with an excess of H 2 (5-10%) in combustion chambers made of steel and refractory bricks. Naib. modern material that prevents HCl contamination - graphite, impregnated phenol-formal. resins. To prevent explosiveness, mix directly in the burner flame. To the top. the combustion chamber area is installed to cool the reaction. up to 150-160°C. Power modern graphite reaches 65 tons/day (in terms of 35% salt). In case of H2 deficiency, dil. is used. process modifications; for example, pass a mixture of Cl 2 and water through a layer of porous hot water:

2Cl 2 + 2H 2 O + C: 4HCl + CO 2 + 288.9 kJ

The temperature of the process (1000-1600 °C) depends on the type and presence of impurities in it, which are (for example, Fe 2 O 3). It is promising to use a mixture of CO with:

CO + H 2 O + Cl 2: 2HCl + CO 2

More than 90% of hydrochloric acid in developed countries is obtained from waste HCl, formed during the dehydrochlorination of org. compounds, chlororg. waste, obtaining non-chlorinated potash. etc. Abgases contain various. quantity of HC1, inert impurities (N 2, H 2, CH 4), poorly soluble in org. substances (,), water-soluble substances (acetic acid), acidic impurities (Cl 2, HF, O 2) and. Application of isothermal advisable when the content of HC1 in exhaust gases is low (but when the content of inert impurities is less than 40%). Naib. Film ones are promising, making it possible to extract from 65 to 85% HCl from the initial exhaust gas.

Naib. Adiabatic schemes are widely used. . Abgases are introduced into the lower part, and (or diluted salt) - countercurrent to the upper one. The salt water is heated to temperature due to the heat of HCl. The change in temperature and HCl is shown in Fig. 1. The temperature is determined by the temperature corresponding to the temperature (max. boiling point of the azeotropic mixture - approx. 110°C).

In Fig. 2 shows a typical adiabatic circuit. HCl from exhaust gases formed during (eg, production). HCl is absorbed in 1, and the residues are poorly soluble in org. the substances are separated from the after in apparatus 2, further purified in the tail column 4 and separators 3, 5 and commercial salt is obtained.



Rice. 1. T-p distribution diagram (curve 1) and

Structural formula

True, empirical, or gross formula: HCl

Chemical composition of hydrochloric acid

Molecular weight: 36.461

Hydrochloric acid(also hydrochloric acid, hydrochloric acid, hydrogen chloride) - a solution of hydrogen chloride (HCl) in water, a strong monobasic acid. Colorless, transparent, caustic liquid, “smoking” in air (technical hydrochloric acid is yellowish in color due to impurities of iron, chlorine, etc.). It is present in a concentration of about 0.5% in the human stomach. The maximum concentration at 20 °C is 38% by weight, the density of such a solution is 1.19 g/cm³. Molar mass 36.46 g/mol. Salts of hydrochloric acid are called chlorides.

Physical properties

The physical properties of hydrochloric acid strongly depend on the concentration of dissolved hydrogen chloride. When solidified, it gives crystal hydrates of the compositions HCl H 2 O, HCl 2H 2 O, HCl 3H 2 O, HCl 6H 2 O.

Chemical properties

  • Interaction with metals in the series of electrochemical potentials up to hydrogen, with the formation of salt and the release of hydrogen gas.
  • Interaction with metal oxides to form soluble salt and water.
  • Interaction with metal hydroxides to form soluble salt and water (neutralization reaction).
  • Interaction with metal salts formed by weaker acids, such as carbonic acid.
  • Interaction with strong oxidizing agents (potassium permanganate, manganese dioxide) with the release of chlorine gas.
  • Reaction with ammonia to form thick white smoke consisting of tiny crystals of ammonium chloride.
  • A qualitative reaction to hydrochloric acid and its salts is its interaction with silver nitrate, which forms a cheesy precipitate of silver chloride, insoluble in nitric acid.

Receipt

Hydrochloric acid is prepared by dissolving hydrogen chloride gas in water. Hydrogen chloride is produced by burning hydrogen in chlorine; the acid obtained in this way is called synthetic. Hydrochloric acid is also obtained from exhaust gases - by-product gases formed during various processes, for example, during the chlorination of hydrocarbons. The hydrogen chloride contained in these gases is called free gas, and the acid thus obtained is called free gas. In recent decades, the share of gas-free hydrochloric acid in production volume has gradually increased, displacing acid produced by burning hydrogen in chlorine. But hydrochloric acid obtained by burning hydrogen in chlorine contains fewer impurities and is used when high purity is required. In laboratory conditions, a method developed by alchemists is used, which consists of the action of concentrated sulfuric acid on table salt. At temperatures above 550 °C and excess table salt, interaction is possible. It is possible to obtain by hydrolysis of magnesium and aluminum chlorides (hydrated salt is heated). These reactions may not proceed to completion with the formation of basic chlorides (oxychlorides) of variable composition, for example. Hydrogen chloride is highly soluble in water. Thus, at 0 °C, 1 volume of water can absorb 507 volumes of HCl, which corresponds to an acid concentration of 45%. However, at room temperature the solubility of HCl is lower, so in practice 36% hydrochloric acid is usually used.

Application

Industry

  • It is used in hydrometallurgy and electroplating (pickling, pickling), for cleaning the surface of metals during soldering and tinning, for producing chlorides of zinc, manganese, iron and other metals. In a mixture with surfactants, it is used to clean ceramic and metal products (inhibited acid is required here) from contamination and disinfection.
  • It is registered in the food industry as an acidity regulator (food additive E507). Used to make seltzer (soda) water.

Medicine

  • A natural constituent of human gastric juice. In a concentration of 0.3-0.5%, usually mixed with the enzyme pepsin, it is administered orally in case of insufficient acidity.

Features of treatment

Highly concentrated hydrochloric acid is a caustic substance that causes severe chemical burns if it comes into contact with the skin. Contact with eyes is especially dangerous. To neutralize burns, use a weak alkali solution, usually baking soda. When opening vessels with concentrated hydrochloric acid, hydrogen chloride vapors, attracting air moisture, form a fog that irritates the eyes and respiratory tract of humans. Reacting with strong oxidizing agents (bleach, manganese dioxide, potassium permanganate) forms toxic chlorine gas. In the Russian Federation, the circulation of hydrochloric acid with a concentration of 15% or more is limited.

What is a hydrochloric acid solution? It is a compound of water (H2O) and hydrogen chloride (HCl), which is a colorless thermal gas with a characteristic odor. Chlorides dissolve well and break down into ions. Hydrochloric acid is the most famous compound that forms HCl, so we can talk about it and its features in detail.

Description

A solution of hydrochloric acid belongs to the class of strong. It is colorless, transparent and caustic. Although technical hydrochloric acid has a yellowish color due to the presence of impurities and other elements. The air “smoke”.

It is worth noting that this substance is present in the body of every person. In the stomach, to be more precise, in a concentration of 0.5%. Interestingly, this amount is enough to completely destroy a razor blade. The substance will corrode it in just a week.

Unlike sulfuric acid, by the way, the mass of hydrochloric acid in solution does not exceed 38%. We can say that this indicator is a “critical” point. If you start to increase the concentration, the substance will simply evaporate, as a result of which hydrogen chloride will simply evaporate along with the water. Plus, this concentration is maintained only at 20 °C. The higher the temperature, the faster evaporation occurs.

Interaction with metals

A solution of hydrochloric acid can undergo many reactions. First of all, with metals that come before hydrogen in the series of electrochemical potentials. This is the sequence in which the elements proceed as their inherent measure, the electrochemical potential (φ 0), increases. This indicator is extremely important in half-reactions of cation reduction. In addition, it is this series that demonstrates the activity of metals in redox reactions.

So, interaction with them occurs with the release of hydrogen in the form of gas and the formation of salt. Here is an example of a reaction with sodium, a soft alkali metal: 2Na + 2HCl → 2NaCl +H 2.

With other substances, interactions proceed according to similar formulas. This is what the reaction with aluminum, a light metal, looks like: 2Al + 6HCl → 2AlCl 3 + 3H 2.

Reactions with oxides

Hydrochloric acid solution also interacts well with these substances. Oxides are binary compounds of an element with oxygen that have an oxidation state of -2. All known examples are sand, water, rust, dyes, carbon dioxide.

Hydrochloric acid does not interact with all compounds, but only with metal oxides. The reaction also produces soluble salt and water. An example is the process that occurs between an acid and magnesium oxide, an alkaline earth metal: MgO + 2HCl → MgCl 2 + H 2 O.

Reactions with hydroxides

This is the name given to inorganic compounds that contain a hydroxyl group -OH, in which the hydrogen and oxygen atoms are connected by a covalent bond. And, since a solution of hydrochloric acid reacts only with metal hydroxides, it is worth mentioning that some of them are called alkalis.

So the resulting reaction is called neutralization. Its result is the formation of a weakly dissociating substance (i.e. water) and salt.

An example is the reaction of a small volume of solution of hydrochloric acid and barium hydroxide, a soft alkaline earth malleable metal: Ba(OH) 2 + 2HCl = BaCl 2 + 2H 2 O.

Interaction with other substances

In addition to the above, hydrochloric acid can react with other types of compounds. In particular with:

  • Metal salts that are formed by other, weaker acids. Here is an example of one of these reactions: Na 2 Co 3 + 2HCl → 2NaCl + H 2 O + CO 2. Shown here is the interaction with a salt formed by carbonic acid (H 2 CO 3).
  • Strong oxidizing agents. With manganese dioxide, for example. Or with potassium permanganate. Such reactions are accompanied by the release of chlorine. Here is one example: 2KMnO 4 +16HCl → 5Cl 2 + 2MnCl 2 + 2KCl + 8H 2 O.
  • Ammonia. This is hydrogen nitride with the formula NH 3, which is a colorless but pungent-smelling gas. The consequence of its reaction with a solution of hydrochloric acid is a mass of thick white smoke consisting of small crystals of ammonium chloride. Which, by the way, is known to everyone as ammonia (NH 4 Cl). The interaction formula is as follows: NH 3 + HCl → NH 4 CL.
  • Silver nitrate is an inorganic compound (AgNO 3), which is a salt of nitric acid and silver metal. As a result of the contact of a hydrochloric acid solution with it, a qualitative reaction occurs - the formation of a cheesy precipitate of silver chloride. Which does not dissolve in nitrogen. It looks like this: HCL + AgNO 3 → AgCl↓ + HNO 3 .

Obtaining the substance

Now we can talk about what is done to form hydrochloric acid.

First, by burning hydrogen in chlorine, the main component, hydrogen chloride gas, is obtained. Which is then dissolved in water. The result of this simple reaction is the formation of a synthetic acid.

This substance can also be obtained from exhaust gases. These are chemical waste (by-product) gases. They are formed through a variety of processes. For example, during the chlorination of hydrocarbons. The hydrogen chloride contained in them is called off-gas. And the acid obtained in this way, respectively.

It should be noted that in recent years the share of waste substances in the total volume of its production has been increasing. And the acid formed due to the combustion of hydrogen in chlorine is displaced. However, to be fair, it should be noted that it contains fewer impurities.

Use in everyday life

Many cleaning products that householders use regularly contain a certain proportion of hydrochloric acid solution. 2-3 percent, and sometimes less, but it is there. That is why, when putting the plumbing in order (washing tiles, for example), you need to wear gloves. Highly acidic products can harm the skin.

The solution is also used as a stain remover. It helps remove ink or rust from clothes. But for the effect to be noticeable, you need to use a more concentrated substance. A 10% hydrochloric acid solution is suitable. By the way, it removes scale perfectly.

It is important to store the substance correctly. Keep the acid in glass containers and in places where animals and children cannot reach. Even a weak solution that gets on the skin or mucous membrane can cause a chemical burn. If this happens, it is necessary to immediately rinse the areas with water.

In the field of construction

The use of hydrochloric acid and its solutions is a popular way to improve many construction processes. For example, it is often added to a concrete mixture to increase frost resistance. In addition, this way it hardens faster, and the resistance of the masonry to moisture increases.

Hydrochloric acid is also used as a limestone remover. Its 10 percent solution is the best way to combat dirt and marks on red brick. It is not recommended to use it to clean others. The structure of other bricks is more sensitive to the effects of this substance.

In medicine

In this area under consideration, the substance is also actively used. Dilute hydrochloric acid has the following effects:

  • Digests proteins in the stomach.
  • Stops the development of malignant tumors.
  • Helps in the treatment of cancer.
  • Normalizes acid-base balance.
  • Serves as an effective remedy for the prevention of hepatitis, diabetes, psoriasis, eczema, rheumatoid arthritis, cholelithiasis, rosacea, asthma, urticaria and many other ailments.

Did you come up with the idea of ​​diluting the acid and using it internally in this form, and not as part of medications? This is practiced, but it is strictly forbidden to do this without medical advice and instructions. By incorrectly calculating the proportions, you can swallow an excess of hydrochloric acid solution and simply burn your stomach.

By the way, you can still take medications that stimulate the production of this substance. And not only chemical ones. The same calamus, peppermint and wormwood contribute to this. You can make decoctions based on them yourself and drink them for prevention.

Burns and poisoning

No matter how effective this remedy is, it is dangerous. Hydrochloric acid, depending on the concentration, can cause four degrees of chemical burns:

  1. There is only redness and pain.
  2. Blisters with clear liquid and swelling appear.
  3. Necrosis of the upper layers of skin is formed. The blisters fill with blood or cloudy contents.
  4. The lesion reaches the tendons and muscles.

If the substance somehow gets into your eyes, you need to rinse them with water and then with a soda solution. But in any case, the first thing you need to do is call an ambulance.

If acid gets inside, it can cause acute pain in the chest and abdomen, swelling of the larynx, and bloody vomit. As a result - severe pathologies of the liver and kidneys.

And the first signs of vapor poisoning include a dry, frequent cough, choking, damage to teeth, burning in the mucous membranes and abdominal pain. The first emergency aid is washing and rinsing the mouth with water, as well as access to fresh air. Only a toxicologist can provide real help.

Hydrochloric acid is an inorganic substance, a monobasic acid, one of the strongest acids. Other names are also used: hydrogen chloride, hydrochloric acid, hydrochloric acid.

Properties

Acid in its pure form is a colorless and odorless liquid. Industrial acid usually contains impurities that give it a slightly yellowish tint. Hydrochloric acid is often called “fuming” because it emits hydrogen chloride vapors, which react with moisture in the air and form acid fog.

Very soluble in water. At room temperature, the maximum possible hydrogen chloride content by weight is 38%. An acid concentration greater than 24% is considered concentrated.

Hydrochloric acid actively reacts with metals, oxides, hydroxides, forming salts - chlorides. HCl reacts with salts of weaker acids; with strong oxidizing agents and ammonia.

To determine hydrochloric acid or chlorides, a reaction with silver nitrate AgNO3 is used, which results in the formation of a white cheesy precipitate.

Safety precautions

The substance is very caustic, corrodes skin, organic materials, metals and their oxides. When exposed to air, it releases hydrogen chloride vapors, which cause suffocation, burns to the skin, mucous membranes of the eyes and nose, damage the respiratory system, and destroy teeth. Hydrochloric acid belongs to substances of the 2nd degree of danger (highly dangerous), the maximum permissible concentration of the reagent in the air is 0.005 mg/l. You can work with hydrogen chloride only in filter gas masks and protective clothing, including rubber gloves, an apron, and safety shoes.

When acid spills, wash it off with plenty of water or neutralize it with alkaline solutions. Those affected by acid should be taken out of the danger area, rinse their skin and eyes with water or soda solution, and call a doctor.

The chemical reagent can be transported and stored in glass, plastic containers, as well as in metal containers coated on the inside with a rubber layer. The container must be hermetically sealed.

Receipt

On an industrial scale, hydrochloric acid is produced from hydrogen chloride (HCl) gas. Hydrogen chloride itself is produced in two main ways:
- exothermic reaction of chlorine and hydrogen - thus obtaining a high-purity reagent, for example, for the food industry and pharmaceuticals;
- from accompanying industrial gases - acid based on such HCl is called exhaust gas.

This is interesting

It was hydrochloric acid that nature “entrusted” with the process of breaking down food in the body. The concentration of acid in the stomach is only 0.4%, but this is enough to digest a razor blade in a week!

Acid is produced by the cells of the stomach itself, which is protected from this aggressive substance by the mucous membrane. However, its surface is renewed daily to restore damaged areas. In addition to participating in the process of digesting food, acid also performs a protective function, killing pathogens that enter the body through the stomach.

Application

- In medicine and pharmaceuticals - to restore the acidity of gastric juice in case of insufficiency; for anemia to improve the absorption of iron-containing drugs.
— In the food industry it is a food additive, acidity regulator E507, and also an ingredient in seltzer (soda) water. Used in the production of fructose, gelatin, citric acid.
- In the chemical industry - the basis for the production of chlorine, soda, monosodium glutamate, metal chlorides, for example zinc chloride, manganese chloride, ferric chloride; synthesis of organochlorine substances; catalyst in organic syntheses.
— Most of the hydrochloric acid produced in the world is consumed in metallurgy for cleaning workpieces from oxides. For these purposes, an inhibited industrial acid is used, which contains special reaction inhibitors (moderators), due to which the reagent dissolves oxides, but not the metal itself. Metals are also etched with hydrochloric acid; clean them before tinning, soldering, galvanizing.
— Treat the leather before tanning.
— In the mining industry it is in demand for cleaning boreholes from sediments, for processing ores and rock formations.
— In laboratory practice, hydrochloric acid is used as a popular reagent for analytical research and for cleaning vessels from difficult-to-remove contaminants.
— Used in the rubber, pulp and paper industries, and in ferrous metallurgy; for cleaning boilers, pipes, equipment from complex deposits, scale, rust; for cleaning ceramic and metal products.

Hydrochloric acid (hydrochloric acid, an aqueous solution of hydrogen chloride), known as HCl, is a caustic chemical compound. Since ancient times, people have been using this colorless liquid for various purposes, which emits a light smoke in the open air.

Properties of a chemical compound

HCl is used in various areas of human activity. It dissolves metals and their oxides, is absorbed in benzene, ether and water, and does not destroy fluoroplastic, glass, ceramics and graphite. Its safe use is possible when stored and operated in the correct conditions, in compliance with all safety standards.

Chemically pure (CP) hydrochloric acid is formed during gaseous synthesis from chlorine and hydrogen, giving hydrogen chloride. It is absorbed in water, resulting in a solution containing 38-39% HCl at +18 C. An aqueous solution of hydrogen chloride is used in various areas of human activity. The price of chemically pure hydrochloric acid is variable and depends on many components.

Areas of application of aqueous hydrogen chloride solution

The use of hydrochloric acid has become widespread due to its chemical and physical properties:

  • in metallurgy, in the production of manganese, iron and zinc, technological processes, metal purification;
  • in galvanoplasty - during etching and pickling;
  • in the production of soda water to regulate acidity, in the production of alcoholic beverages and syrups in the food industry;
  • for leather processing in light industry;
  • when purifying non-drinking water;
  • for optimization of oil wells in the oil industry;
  • in radio engineering and electronics.

Hydrochloric acid (HCl) in medicine

The most famous property of hydrochloric acid solution is the equalization of the acid-base balance in the human body. Low stomach acidity is treated with a weak solution or drugs. This optimizes the digestion of food and helps fight germs and bacteria that penetrate from the outside. HCl hydrochloric acid helps normalize low levels of gastric acidity and optimizes protein digestion.

Oncology uses HCl to treat tumors and slow down their progression. Hydrochloric acid preparations are prescribed for the prevention of stomach cancer, rheumatoid arthritis, diabetes, asthma, urticaria, cholelithiasis and others. In folk medicine, hemorrhoids are treated with a weak acid solution.

You can find out more about the properties and types of hydrochloric acid.



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