Concentrated hydrochloric acid concentration. Hydrochloric acid: use in everyday life for cleaning pipes

1.2679; G crnt 51.4°C, p crit 8.258 MPa, d crit 0.42 g/cm 3 ; -92.31 kJ / , D H pl 1.9924 kJ / (-114.22 ° C), D H test 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); temperature dependence equation lgp (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. one.

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-value of HC1 in alkyl and aryl halides is low, for example. 0.07 / for C 4 H 9 C1. P-value in the range from -20 to 60 ° C decreases in the series dichloroethane-tri-chloroethane-tetrachloroethane-trichlorethylene. R-value at 10°C in a series is approximately 1 / , in carboxylic esters 0.6 / , in carboxylic esters 0.2 / . In stable R 2 O · НCl are formed. The p-value of HC1 is subject to and is for KCl 2.51 10 -4 (800 ° C), 1.75 10 -4 / (900 ° C), for NaCl 1.90 10 -4 / (900 ° FROM).

Salt to-ta. HCl in water is highly exothermic. process, for infinitely razb. water solution D H 0 Hcl -69.9 kJ / , Cl -- 167.080 kJ/; HC1 is fully ionized. The solubility of HC1 in depends on the t-ry (Table 2) and the partial HC1 in the gas mixture. Density of salt dec. and h at 20 °C are presented in Table. 3 and 4. With an increase in t-ry h hydrochloric decreases, for example: for 23.05% hydrochloric at 25 ° C h 1364 mPa s, at 35 ° C 1.170 mPa s. hydrochloric 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 eutectic. points: - 74.7 ° C (23.0% by mass of HCl); -73.0°C (26.5% HCl); -87.5°C (24.8% HC1, metastable phase). HCl nH 2 O are known, where n = 8.6 (mp. -40 ° С), 4. 3 (mp. -24.4 ° С), 2 (mp. -17.7 °С) and 1 (mp. -15.35°С). crystallizes from 10% hydrochloric acid at -20, from 15% hydrochloric acid at -30, from 20% hydrochloric acid at -60 and from 24% hydrochloric acid at -80°C. The p-value of halides decreases with increasing HCl in hydrochloric acid, which is used for them.

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

FROM hydrochloric acid is chemically very active. Dissolves with the release of H 2 all having negative. ,with me. and forms, allocates free. to-you from such as, etc.

Receipt. In the industry, Hcl get a trace. ways-sulfate, synthetic. and from off-gases (by-products) of a number of processes. The first two methods lose their meaning. So, in the USA in 1965 the share of off-gas salt was 77.6% in the total volume of production, and in 1982-94%.

The production of hydrochloric (reactive, obtained by the sulphate method, synthetic, off-gas) consists in obtaining HCl with the last. his . Depending on the method of heat removal (reaches 72.8 kJ/), the processes are divided into isothermal, adiabatic. and combined.

The sulfate method is based on the 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 the chain p-tion: H 2 + Cl 2 2HCl + 184.7 kJ K p is calculated according to the equation: lgK p \u003d 9554 / T- 0.5331g T + 2.42.

R-tion is initiated by light, moisture, solid porous (, porous Pt) and some miners. in-you ( , ). Synthesis is carried out with an excess of H 2 (5-10%) in combustion chambers made of steel, refractory bricks. Naib. modern HCl pollution prevention material - graphite impregnated with phenol-formald. resins. To prevent an explosive nature, they are mixed directly in the flame of the burner. To the top. the zone of the combustion chambers is installed to cool the reaction. up to 150-160°С. The power of modern graphite reaches 65 tons / day (in terms of 35% hydrochloric acid). In case of H 2 deficiency, decomp. process modifications; for example, a mixture of Cl 2 with water is passed through a layer of porous incandescent:

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 (eg, 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 off-gas HCl, which is formed during and dehydrochlorination of org. compounds, chlororg. waste, obtaining potassium non-chlorinated. etc. Abgazes contain decomp. quantity of HC1, inert impurities (N 2, H 2, CH 4), slightly soluble in org. in-va (, ), water-soluble in-va (acetic acid,), acidic impurities (Cl 2, HF, O 2) and. The use of isothermal it is expedient at a low content of HC1 in exhaust gases (but with the content of inert impurities less than 40%). Naib. promising film, allowing you to extract from the original exhaust gas from 65 to 85% HCl.

Naib. adiabatic schemes are widely used. . Abgases are introduced into the lower. part, and (or dilute hydrochloric) - countercurrent to the top. Salt is heated to t-ry due to the heat of HCl. The change in t-ry and Hcl is given in fig. 1. T-ra is determined by the temperature of the corresponding one (max. t-ra-t. boiling of the azeotropic mixture is approx. 110 ° C).

On fig. 2 shows a typical adiabatic scheme. HCl from off-gases generated during (eg, production). Hcl is absorbed in 1, and the remains of sparingly soluble in org. in-in is separated from after in apparatus 2, further cleaned in tail column 4 and separators 3, 5 and commercial hydrochloric acid is obtained.

Rice. 1. Distribution scheme t-r (curve 1) and

Like acids. The education program provides for the memorization by students of the names and formulas of six representatives of this group. And, looking through the table provided by the textbook, you notice in the list of acids the one that comes first and interested you in the first place - hydrochloric acid. Alas, in the classroom at school, neither the property nor any other information about it is studied. Therefore, those who are eager to gain knowledge outside school curriculum look for additional information in all sorts of sources. But often, many do not find the information they need. And so the topic of today's article is dedicated to this particular acid.

Definition

Hydrochloric acid is a strong monobasic acid. In some sources, it may be called hydrochloric and hydrochloric, as well as hydrogen chloride.

Physical Properties

It is a colorless and fuming caustic liquid in the air (photo on the right). However, technical acid has a yellowish color due to the presence of iron, chlorine and other additives in it. Its largest concentration at a temperature of 20 ° C is 38%. Density of hydrochloric acid with such parameters is equal to 1.19 g / cm 3. But this compound in varying degrees of saturation has completely different data. With a decrease in concentration, the numerical value of molarity, viscosity and melting point decreases, but increases specific heat and boiling point. Solidification of hydrochloric acid of any concentration gives various crystalline hydrates.

Chemical properties

All metals that come before hydrogen in the electrochemical series of their voltage can interact with this compound, forming salts and releasing hydrogen gas. If they are replaced by metal oxides, then the reaction products will be soluble salt and water. The same effect will be in the interaction of hydrochloric acid with hydroxides. If, however, any metal salt (for example, sodium carbonate) is added to it, the residue of which was taken from a weaker acid (carbonic), then chloride of this metal (sodium), water and gas corresponding to the acid residue (in this case- carbon dioxide).

Receipt

The compound now discussed is formed when hydrogen chloride gas, which can be obtained by burning hydrogen in chlorine, is dissolved in water. Hydrochloric acid, which was obtained using this method, is called synthetic. Off-gases can also serve as a source for obtaining this substance. And such hydrochloric acid will be called off-gas. Recently, the level of production of hydrochloric acid using this method is much higher than its production by a synthetic method, although the latter gives the compound in a purer form. These are all ways of getting it in industry. However, in laboratories, hydrochloric acid is obtained in three ways (the first two differ only in temperature and reaction products) using various kinds chemical interactions such as:

Effect of saturated sulfuric acid on sodium chloride at 150°C.
The interaction of the above substances under conditions with a temperature of 550 ° C and above.
Hydrolysis of aluminum or magnesium chlorides.

Application

Hydrometallurgy and electroforming cannot do without the use of hydrochloric acid, where it is needed, in order to clean the surface of metals during tinning and soldering and to obtain chlorides of manganese, iron, zinc and other metals. In the food industry, this compound is known as food additive E507 - there it is an acidity regulator necessary in order to make seltzer (soda) water. Concentrated hydrochloric acid is also found in the gastric juice of any person and helps to digest food. During this process, its degree of saturation decreases, because. this composition is diluted with food. However, with prolonged fasting, the concentration of hydrochloric acid in the stomach gradually increases. And since this compound is very caustic, it can lead to stomach ulcers.

Conclusion

Hydrochloric acid can be both beneficial and harmful to humans. Its contact with the skin leads to the appearance of severe chemical burns, and the vapors of this compound irritate the respiratory tract and eyes. But if you handle this substance carefully, it can come in handy more than once in

Hydrochloric acid tank

One of the strong monobasic acids and is formed when a gas is dissolved hydrogen chloride(HCl) in water, is a clear, colorless liquid with a characteristic odor of chlorine. dilute hydrochloric acid(as well as phosphoric) is often used to remove oxides when soldering metals.

Sometimes the gaseous compound HCl is erroneously called hydrochloric acid. HCl is a gas that, when dissolved in water, forms hydrochloric acid.

Hydrogen chloride It is a colorless gas with a pungent, suffocating odor of chlorine. It goes into a liquid state at -84 0 C, and at -112 0 C it goes into a solid state.

Hydrogen chloride very soluble in water. So at 0 0 C, 500 liters of hydrogen chloride dissolve in 1 liter of water.
In a dry state, hydrogen chloride gas is quite inert, but it can already interact with some organic matter, for example with acetylene (the gas that is released when carbide is lowered into water).

Chemical properties of hydrochloric acid

Chemical reaction with metals:
2HCl + Zn \u003d ZnCl 2 + H 2 - a salt is formed (in this case, a clear solution of zinc chloride) and hydrogen
- chemical reaction with metal oxides:
2HCl + CuO \u003d CuCl 2 + H 2 O - a salt is formed (in this case, a green copper chloride salt solution) and water
- chemical reaction with bases and alkalis (or neutralization reaction)
HCl + NaOH \u003d NaCl + H 2 O - neutralization reaction, - a salt is formed (in this case, a clear solution of sodium chloride) and water.
- chemical reaction with salts (for example, with CaCO 3 chalk):
HCl + СaCO 3 \u003d CaCl 2 + CO 2 + H 2 O - carbon dioxide, water and a clear solution of calcium chloride CaCl 2 are formed.

Getting hydrochloric acid

hydrochloric acid obtained by a chemical reaction of the compound:

H 2 + Cl 2 = HCl - the reaction occurs when elevated temperature

And also in the interaction of table salt and concentrated sulfuric acid:

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

In this reaction, if NaCl is a solid, then HCl is a gas hydrogen chloride which, when dissolved in water, forms hydrochloric acid

There are complex chemicals that are similar in chemical structure to hydrochloric acid, but at the same time contain from one to four oxygen atoms in the molecule. These substances can be called oxygenated acids. With an increase in the number of oxygen atoms, the stability of the acid and its oxidizing ability increase.

To oxygenated acids following:

hypochlorous (HClO),
chloride (HClO 2),
chloric (HClO 3),
chloride (HClO 4).

Each of these chemical complex substances has all properties of acids and is capable of forming salts. Hypochlorous acid(HClO) forms hypochlorites, for example, the compound NaClO is sodium hypochlorite. Hypochlorous acid itself is formed when chlorine is dissolved in cold water by chemical reaction:

H 2 O + Cl 2 \u003d HCl + HClO,

As you can see, in this reaction two acids are formed at once - hydrochloric HCl and hypochlorous HClO. But the latter is an unstable chemical compound and gradually turns into hydrochloric acid;

Chloride HClO 2 forms chlorites, salt NaClO 2 - sodium chlorite;
chlorine(HClO 3) - chlorates, KClO 3 compound, - potassium chlorate (or Berthollet salt) - by the way, this substance is widely used in the manufacture of matches.

And finally, the strongest of the known monobasic acids - chloride(HClO 4) - colorless, fuming in air, highly hygroscopic liquid, - forms perchlorates, for example, KClO 4 - potassium perchlorate.

Salts formed hypochlorous HClO and chloride HClO 2 acids are not stable in the free state and are strong oxidizing agents in aqueous solutions. But the salts formed chlorine HClO 3 and chloride HClO 4 acids based on alkali metals (for example, Bertolet's salt KClO 3) are quite stable and do not exhibit oxidizing properties.

Hydrochloric acid is an inorganic substance, 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. Technical acid usually contains impurities that give it a slightly yellowish tint. Hydrochloric acid is often referred to as "fuming" because it releases hydrogen chloride vapor, which reacts with atmospheric moisture to form an acid mist.

It dissolves very well in water. At room temperature, the maximum possible mass content of hydrogen chloride is 38%. An acid concentration greater than 24% is considered concentrated.

Hydrochloric acid actively reacts with metals, oxides, hydroxides, forming salts - chlorides. HCl interacts 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, as a result of which a white cheesy precipitate precipitates.

Safety

The substance is very caustic, corrosive to skin, organic materials, metals and their oxides. In the air, it emits 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 the substances of the 2nd degree of danger (highly dangerous), the MPC of the reagent in the air is 0.005 mg/l. It is possible to work with hydrogen chloride only in filtering gas masks and protective clothing, including rubber gloves, an apron, safety shoes.

If acid is spilled, it is washed off with large amounts of water or neutralized with alkaline solutions. Victims of acid should be taken out of the danger zone, rinse the skin and eyes with water or soda solution, call a doctor.

It is allowed to transport and store a chemical reagent in a glass, plastic container, as well as in a metal container, covered from the inside with a rubber layer. The container must be hermetically sealed.

Receipt

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

It's curious

It is to hydrochloric acid that nature "entrusted" the process of splitting 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!

The 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 updated daily to repair damaged areas. In addition to participating in the process of digestion of 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 its insufficiency; with anemia to improve the absorption of iron-containing drugs.
- In the food industry, this is a food additive, acidity regulator E507, as well as an ingredient in seltzer (soda) water. Used in the manufacture of fructose, gelatin, citric acid.
- In the chemical industry - the basis for the production of chlorine, soda, sodium glutamate, metal chlorides, for example zinc chloride, manganese chloride, iron chloride; synthesis of organochlorine substances; catalyst in organic synthesis.
- Most of the hydrochloric acid produced in the world is used in metallurgy to clean workpieces from oxides. For these purposes, an inhibited technical acid is used, which contains special inhibitors (retarders) of the reaction, due to which the reagent dissolves oxides, but not the metal itself. Metals are also poisoned with hydrochloric acid; clean them before tinning, soldering, galvanizing.
— Treat the skin before tanning.
- In the mining industry, it is in demand for cleaning boreholes from deposits, for processing ores and rock formations.
— In laboratory practice, hydrochloric acid is used as a popular reagent for analytical studies, for cleaning vessels from hard-to-remove contaminants.
– It is used in the rubber, pulp and paper industry, in ferrous metallurgy; for cleaning boilers, pipes, equipment from complex deposits, scale, rust; for cleaning ceramic and metal products.

Like acids. The education program provides for the memorization by students of the names and formulas of six representatives of this group. And, looking through the table provided by the textbook, you notice in the list of acids the one that comes first and interested you in the first place - hydrochloric acid. Alas, in the classroom at school, neither the property nor any other information about it is studied. Therefore, those who are eager to gain knowledge outside the school curriculum are looking for additional information in all sorts of sources. But often, many do not find the information they need. And so the topic of today's article is dedicated to this particular acid.

Definition

Hydrochloric acid is a strong monobasic acid. In some sources, it may be called hydrochloric and hydrochloric, as well as hydrogen chloride.

Physical Properties

It is a colorless and fuming caustic liquid in the air (photo on the right). However, technical acid has a yellowish color due to the presence of iron, chlorine and other additives in it. Its largest concentration at a temperature of 20 ° C is 38%. The density of hydrochloric acid with such parameters is 1.19 g/cm 3 . But this compound in varying degrees of saturation has completely different data. With a decrease in concentration, the numerical value of molarity, viscosity and melting point decrease, but the specific heat capacity and boiling point increase. Solidification of hydrochloric acid of any concentration gives various crystalline hydrates.

Chemical properties

Receipt

Effect of saturated sulfuric acid on sodium chloride at 150°C.
The interaction of the above substances under conditions with a temperature of 550 ° C and above.
Hydrolysis of aluminum or magnesium chlorides.

Application

Conclusion

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Properties

Safety

Receipt

It's curious

Application

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