Hydrochloric acid is one of the most powerful and dangerous substances for humans on the list of AHOV. However, it is surprising that it exists in the body of every person: hydrochloric acid is an integral part of gastric juice and plays an important role in the digestive process. In an amount of 0.2%, it promotes the transition of food masses from the stomach to the duodenum and neutralizes microbes that enter the stomach from external environment. It also activates the enzyme pepsinogen, is involved in the formation of secretin and some other hormones that stimulate the activity of the pancreas. For this purpose, it is used in medicine, prescribing its solution to patients to increase the acidity of gastric juice. In general, hydrochloric acid has wide application in our life. For example, in heavy industry - to obtain chlorides of various metals, in the textile industry - to obtain synthetic dyes; for the food industry, acetic acid is made from it, for the pharmaceutical industry - activated carbon. It is also found in various adhesives and hydrolysis alcohol. It is used for etching metals, cleaning various vessels, casing pipes of boreholes from carbonates, oxides and other sediments and contaminants. In metallurgy, ores are treated with hydrochloric acid; in the leather industry, leather is treated before tanning and dyeing. Hydrochloric acid is transported in glass bottles or gummed (coated with a layer of rubber) metal vessels, as well as in plastic containers.

What is it as a chemical substance?

Hydrochloric acid, or hydrochloric acid, is water solution hydrogen chloride HCl, which is a clear, colorless liquid with a pungent odor of hydrogen chloride. The technical variety of acid has a yellowish-green color due to impurities of chlorine and iron salts. The maximum concentration of hydrochloric acid is about 36% HCl; such a solution has a density of 1.18 g/cm3. Concentrated acid "smokes" in air, since the escaping gaseous HCl forms tiny droplets of hydrochloric acid with water vapor.

Despite this characteristic, hydrochloric acid is neither flammable nor explosive when exposed to air. But at the same time, it is one of the strongest acids and dissolves (with the release of hydrogen and the formation of salts - chlorides) all metals in the series of voltages up to hydrogen. Chlorides are also formed by the interaction of hydrochloric acid with metal oxides and hydroxides. With strong oxidizing agents, it behaves like a reducing agent.

Salts of hydrochloric acid are chlorides and, with the exception of AgCl, Hg2Cl2, are highly soluble in water. Materials such as glass, ceramics, porcelain, graphite, and fluoroplastic are resistant to hydrochloric acid.

Hydrochloric hydrogen chloride is obtained in water, which, in turn, is either directly synthesized from hydrogen and chlorine, or obtained by the action of sulfuric acid on sodium chloride.

Commercially available (technical) hydrochloric acid has a strength of at least 31% HCl (synthetic) and 27.5% HCl (from NaCl). Commercial acid is called concentrated if it contains 24% or more HCl; if the HCl content is less, then the acid is called dilute.

Definition and formula of hydrochloric acid

DEFINITION

Hydrochloric acid (hydrochloric acid, hydrochloric acid, hydrogen chloride) is a solution of hydrogen chloride \(\\mathrm(HCl)\) in water.

Hydrochloric acid formula

Formula - \(\ \mathrm(HCl) \)

Molar mass equal to 36.46 g/mol.

Physical properties - colorless caustic liquid, "smokes" in air.

Technical hydrochloric acid has yellow due to the presence of impurities of iron, chlorine and other substances

The maximum concentration in the solution at \(\ 20^(\circ) \mathrm(C) \) is 38%, the density of this solution is 1.19 g/cm3. Molar mass 36.46 g/mol.

Hydrochloric acid is a strong monobasic acid, dissociation constant.

Forms salts - chlorides.

Chemical properties of hydrochloric acid

It interacts with metals that are in the electrochemical series of voltages up to hydrogen with the formation of the corresponding chlorides and the release of hydrogen:

\(\ Z n+2 H C l=Z n C l_(2)+H_(2) \uparrow \)

Interacts with metal oxides to form soluble salts and water:

\(\ M g O+2 H C l=M g C l_(2)+H_(2) O \)

Reacts with metal hydroxides to form soluble chlorides and water:

\(\ A l(O H)_(3)+3 H C l=A l C l_(3)+3 H_(2) O \)

Interacts with metal salts formed by weaker acids:

\(\ \mathrm(Na)_(2) \mathrm(CO)_(3)+2 \mathrm(HCl)=2 \mathrm(NaCl)+\mathrm(H)_(2) \mathrm(O) +\mathrm(CO)_(2) \uparrow \)

Reacts with strong oxidants (potassium permanganate, manganese dioxide) to release chlorine:

\(\ 2 K M n O_(4)+16 H C l=5 C l_(2) \uparrow+2 M n C l_(2)+2 K C l+8 H_(2) O \)

Reacts with ammonia to form thick white smoke consisting of tiny crystals of ammonium chloride:

\(\ N H_(3)+H C l=N H_(4) C l \)

Qualitative reaction on hydrochloric acid and its salts is a reaction with silver nitrate, which results in the formation of a white cheesy precipitate of silver chloride, insoluble in nitric acid:

\(\ H C l+A g N O_(3)=A g C l \downarrow+H N O_(3) \)

Hydrochloric acid is prepared by dissolving hydrogen chloride gas in water.

Application

Hydrochloric acid is used in hydrometallurgy and electroforming (etching, pickling), to clean the surface of metals during soldering and tinning, to obtain metal chlorides (zinc, manganese, iron, etc.). Mixtures of hydrochloric acid with surfactants are used to clean ceramic and metal products from contamination and disinfection.

In the food industry, hydrochloric acid is used as an acidity regulator \(\\mathrm(pH)\) , food additive E507. It is a natural component of human gastric juice.

Concentrated hydrochloric acid is a corrosive substance that causes severe chemical burns if it comes into contact with the skin. Acid in the eyes is especially dangerous. To neutralize burns, a solution of weak alkali (baking soda) is used.

Examples of problem solving

Calculate the normality of a hydrochloric acid solution if 19.2 ml of a 0.1 N sodium hydroxide solution was used to titrate 20 ml of it.

We write the equation for the titration reaction:

\(\ H C l+N a O H=N a C l+H_(2) O \)

Let us write down the law of equivalents for the given titration process:

\(\ V_(N a O H) \cdot N_(N a O H)=V_(H C l) \cdot N_(H C l) \)

We express the normal concentration of a hydrochloric acid solution:

\(\ N_(H C l)=\frac(V_(N a O H) \cdot N_(N a O H))(V_(H C l))=\frac(19,2 \cdot 0,1)(20) \u003d 0.096 \)

The normality of a hydrochloric acid solution is 0.096 N.

A solution of hydrochloric acid \ (\ \mathrm (HCl) \) with a volume of 1.8 ml (density 1.18 g / ml) with a mass fraction of a substance of 36% was diluted with water to 1 liter. Find \(\ _(1) \mathrm(pH) \) of the resulting solution.

We write the equation for the dissociation of hydrochloric acid:

\(\ H C l=H^(+)+C l^(-) \)

Let's find the mass of the initial solution of hydrochloric acid by the formula:

\(\ m=\rho \cdot V\)

where \(\ \rho \) is the density of the solution, \(\ \mathrm(V) \) is the volume of the solution.

\(\ m_(p-p a)=1.18 \cdot 1.8=2.124 g.\)

Find the mass of hydrochloric acid in solution. The expression for the mass fraction of a substance in solution:

\(\ \omega=\frac(m_(b-b a))(m_(p-p a)) \)

If the hydrochloric acid solution is 36%, then the mass fraction of hydrochloric acid in it will be equal to 0.36.

Express the mass of hydrochloric acid:

\(\ m_(H C l)=\omega \cdot m_(p-p a)=0.36 \cdot 2.124=0.765 \)

Considering that the molar mass of hydrochloric acid is 36.5 g/mol, we calculate the amount of substance \(\ \mathrm(HCl) \) in solution

\(\ n_(H C l)=\frac(m_(H C l))(M_(H C l))=\frac(0.765)(36.5)=0.021 \) mol

Since the initial volume of the solution was diluted with water to 1 liter, we find the molar concentration of the resulting hydrochloric acid solution using the formula:

\(\ C_(M)(H C l)=\frac(n_(H C l))(V)=\frac(0.021)(1)=0.021 \) mol/l

Hydrochloric acid is a strong acid, it dissociates completely in an aqueous solution, so the concentration of hydrogen ions will be equal to the concentration of the acid:

\(\ \left \u003d M (H C l) \u003d 0.021 \) mol / l

The pH of the solution is calculated by the formula:

\(\ p H=-l g\left=-\lg (0.021)=1.678=1.678 \)

The pH of the resulting solution is 1.678

Hydrochloric acid is an aqueous solution of hydrogen chloride. It is a suspension with a pronounced odor. Its color is transparent. It is a strong monobasic acid, which is particularly caustic. When interacting with air, it begins to "smoke". If you pay attention to the technical solution, then it has a slight lemon tint due to the presence of certain impurities of iron and chlorine in it. In a small amount, this component is present in human gastric juice. The salts of this solution are called chlorides.

Concerning physical properties of the substance under consideration, they strongly depend on the concentration of dissolved hydrogen chloride. It is often diluted acid that is used, which contains no more than ten percent hydrogen chloride.

It should be noted that it is a volatile compound, because when heated it can completely evaporate. In addition, the substance reacts with an impressive amount of various metals. But, not all of them can be influenced by this solution. For example, such as gold, silver, lead, tungsten, and platinum do not dissolve with this acid. But some metals that are not precious, when dissolved in hydrochloric acid, turn into chlorides. Zinc is one of them.

Applications of hydrochloric acid

The use of this compound is varied. For example, the food industry uses this substance to create a special food additive E507. The latter is used for the production of alcoholic beverages, in particular for the manufacture of vodka and all kinds of syrups. The use of hydrochloric acid to create drinks and food products is explained by the fact that the compound acts as a so-called regulator of the acid state of food products.

Use in metallurgy

Acid is still actively used in metallurgy. But, it should be noted that it is the technical variety of the substance that is most in demand here. It is used for high-quality and effective cleaning of metals before direct soldering or tinning.

It is important to note that it is also used in hydrometallurgy and electroforming. With the help of hydrochloric acid, etching and pickling are carried out.

Application in medicine

Among other things, the substance is also used in medicine. This is because it is a natural part of human gastric juice. In a minimum concentration, it is prescribed for oral administration in a mixture with the enzyme pepsin. This compound is necessary for insufficient acidity.

It is important to pay attention to the fact that the use of hydrochloric acid for industrial purposes does not create any problems, it is necessary to approach the choice of the variety of this compound and its concentration with the utmost responsibility.

Home use

Few people thought about the composition of the popular detergents that we use every day to clean various surfaces. Few are aware that some of these chemical compositions contain hydrochloric acid. The most effective are chemicals designed to clean toilets. They are highly acidic. It is in their composition that this active ingredient is present. In order to protect your hands from the negative effects of an aggressive composition, you must work exclusively with thick rubber gloves. Thanks to them, you can protect your hands from rashes and allergies.

Thrifty housewives use this solution at home as an effective remedy for removing stains. It also makes it possible to get rid of ugly traces of rust and ink on clothes. Acid must be stored in special high-strength glass containers in places that are inaccessible to children. If this acid accidentally gets on vulnerable mucous membranes or on bare skin, then immediately wash the affected area of ​​\u200b\u200bthe skin under running water. The use of this ingredient at home should be done in accordance with the main and generally accepted safety rules.

Hydrochloric acid is used not only to deal with difficult stains on clothes. It is also a great remedy for pimple control. In order not to worsen the situation when cleaning contaminated dishes, a solution of a certain concentration should be used. For this purpose, it is inhibited acid that is suitable, the use of which allows you to keep the dishes safe and sound.

To keep your home and clothes perfectly clean, you need to purchase hydrochloric acid for yourself. She, as you know, can be dangerous to humans, so you need to be extremely careful when handling it. May cause severe chemical burns if mishandled. Especially destructive is its contact with the mucous membrane of the eye.

Application in construction

Few people know that hydrochloric acid is used to improve and modernize many processes in construction. It is added to concrete to increase its frost resistance. In addition, the composition hardens much faster, and the masonry becomes resistant to moisture. Another acid is used as an oxidizing agent from limestone.

Hydrochloric acid production

This substance is obtained by the complete dissolution of hydrogen chloride in the form of a gas in a normal aqueous medium. But hydrogen chloride itself appears as a result of the combustion of hydrogen in chlorine. The compound thus obtained is called synthetic. The acid under consideration can also be obtained from special off-gases - by-product gases that appear during various processes. For example, when chlorinating hydrocarbons. It is important to note that hydrogen chloride, which is present in these gases, is called off-gas. IN last years the amount of off-gas acid in the volume of production is constantly increasing, displacing acid, which is obtained by burning hydrogen in chlorine. But, nevertheless, the hydrochloric acid obtained by such a simple method has fewer foreign ingredients in its composition and is used if it is necessary to achieve maximum purity. Hydrogen chloride is highly soluble in water.

In contact with

- (HCl), aqueous solution of hydrogen chloride, colorless gas with a pungent odor. Obtained by the action of sulfuric acid on common salt, as a by-product of the chlorination of hydrocarbons, or by the reaction of hydrogen and chlorine. Hydrochloric acid is used for ... ... Scientific and technical encyclopedic dictionary

Hydrochloric acid- - HCl (SC) (hydrochloric acid, hydrochloric acid, hydrogen chloride) is a solution of hydrogen chloride (HCl) in water, an antifreeze additive. It is a colorless liquid with a pungent odor, without suspended particles. ... ... Encyclopedia of terms, definitions and explanations of building materials

- (hydrochloric acid) solution of hydrogen chloride in water; strong acid. A colorless liquid fuming in air (technical hydrochloric acid is yellowish due to impurities of Fe, Cl2, etc.). Maximum concentration (at 20 .C) 38% by mass, ... ... Big encyclopedic Dictionary

HYDROCHLORIC ACID- (Acidum muriaticum, Acid, hydrochloricum), a solution of hydrogen chloride (HC1) in water. In nature, it occurs in the water of some sources of volcanic origin, and is also found in gastric juice (up to 0.5%). Hydrogen chloride can be obtained ... Big Medical Encyclopedia

HYDROCHLORIC ACID- (hydrochloric acid, hydrochloric acid) a strong monobasic volatile acid with a pungent odor, an aqueous solution of hydrogen chloride; the maximum concentration is 38% by mass, the density of such a solution is 1.19 g/cm3. Used in... ... Russian encyclopedia of labor protection

HYDROCHLORIC ACID- (hydrochloric acid) HCl aqueous solution of hydrogen chloride, strong monobasic acid, volatile, with a pungent odor; impurities of iron, chlorine stain it yellowish. The concentrated S. to sell contains 37% ... ... Great Polytechnic Encyclopedia

Exist., Number of synonyms: 1 acid (171) ASIS Synonym Dictionary. V.N. Trishin. 2013 ... Synonym dictionary

Modern Encyclopedia

Hydrochloric acid- HYDROGENIC ACID, aqueous solution of hydrogen chloride HCl; a fuming liquid with a pungent odor. Hydrochloric acid is used to obtain various chlorides, pickling metals, processing ores, in the production of chlorine, soda, rubber, etc. ... ... Illustrated Encyclopedic Dictionary

- (hydrochloric acid), a solution of hydrogen chloride in water; strong acid. A colorless liquid "fuming" in air (technical hydrochloric acid is yellowish due to impurities of Fe, Cl2, etc.). Maximum concentration (at 20°C) 38% by mass,… … encyclopedic Dictionary

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Hydrogen chloride is a gas about 1.3 times heavier than air. It is colorless, but with a sharp, suffocating and characteristic odor. At a temperature of minus 84C, hydrogen chloride passes from a gaseous to a liquid state, and at minus 112C it solidifies. Hydrogen chloride dissolves in water. One liter of H2O can absorb up to 500 ml of gas. Its solution is called hydrochloric or hydrochloric acid. Concentrated hydrochloric acid at 20C is characterized by the maximum possible basic substance, equal to 38%. The solution is a strong monobasic acid (it smokes in air, and forms an acid mist in the presence of moisture), it also has other names: hydrochloric acid, and according to Ukrainian nomenclature - chloride acid. Chemical formula can be presented in this form: HCl. The molar mass is 36.5 g/mol. The density of concentrated hydrochloric acid at 20C is 1.19 g/cm³. This is a harmful substance that belongs to the second hazard class.

In a "dry" form, hydrogen chloride cannot interact even with active metals, but in the presence of moisture, the reaction proceeds quite vigorously. This strong hydrochloric acid is capable of reacting with all metals that are to the left of hydrogen in the voltage series. In addition, it interacts with basic and amphoteric oxides, bases, as well as with salts:

• Fe + 2HCl → FeCl2 + H2;
• 2HCl + CuO → CuCl2 + H2O;
• 3HCl + Fe(OH)3 → FeCl3 + 3H2O;
• 2HCl + Na2CO3 → 2NaCl + H2O + CO2;
• HCl + AgNO3 → AgCl↓ + HNO3.

In addition to the general properties characteristic of each strong acid, concentrated hydrochloric acid reacts with various oxidizing agents, releasing free chlorine. Salts of this acid are called chlorides. Almost all of them dissolve well in water and completely dissociate into ions. Slightly soluble are: lead chloride PbCl2, silver chloride AgCl, monovalent mercury chloride Hg2Cl2 (calomel) and monovalent copper chloride CuCl. Hydrogen chloride is capable of entering into an addition reaction to a double or triple bond, with the formation of chlorine derivatives of organic compounds.

Under laboratory conditions, hydrogen chloride is obtained by exposure to dry concentrated sulfuric acid. The reaction under different conditions can proceed with the formation of sodium salts (acidic or medium):

• H2SO4 + NaCl → NaHSO4 + HCl
• H2SO4 + 2NaCl → Na2SO4 + 2HCl.

The first reaction goes to completion at low heating, the second - at higher temperatures. Therefore, in the laboratory, it is better to obtain hydrogen chloride by the first method, for which the amount of sulfuric acid is recommended to be taken from the calculation of obtaining the acid salt NaHSO4. Then, by dissolving hydrogen chloride in water, hydrochloric acid is obtained. In industry, it is obtained by burning hydrogen in an atmosphere of chlorine or by acting on dry sodium chloride (only the second with concentrated sulfuric acid. Hydrogen chloride is also obtained as a by-product during the chlorination of saturated organic compounds. In industry, hydrogen chloride obtained by one of the above methods is dissolved in special towers in which liquid is passed from top to bottom, and gas is supplied from bottom to top, that is, according to the principle of counterflow.

Hydrochloric acid is transported in special rubberized tanks or containers, as well as in polyethylene barrels with a capacity of 50 liters or glass bottles with a capacity of 20 liters. When there is a risk of formation of explosive hydrogen-air mixtures. Therefore, the contact of the hydrogen formed as a result of the reaction with air, as well as (with the help of anti-corrosion coatings) the contact of acid with metals, must be completely excluded. Before removing the apparatus and pipelines, where it was stored or transported, for repair, it is necessary to carry out nitrogen purges and control the state of the gas phase.

Hydrogen chloride is widely used in industrial production and in laboratory practice. It is used to obtain salts and as a reagent in analytical studies. Technical hydrochloric acid is produced in accordance with GOST 857-95 (the text is identical to the international standard ISO 905-78), the reagent is in accordance with GOST 3118-77. The concentration of the technical product depends on the brand and grade and can be 31.5%, 33% or 35%, and externally the product is yellowish in color due to the content of impurities of iron, chlorine and other chemicals. The reactive acid should be a colorless and transparent liquid with a mass fraction of 35 to 38%.