Hydrochloric acid is a clear, colorless or yellowish liquid without suspended or emulsified particles.
Hydrochloric acid is a solution of gaseous hydrogen chloride HCl in water. The latter is a hygroscopic colorless gas with a pungent odor. The commonly used concentrated hydrochloric acid contains 36-38% hydrogen chloride and has a density of 1.19 g/cm3. Such an acid smokes in air, as gaseous HCl is released from it; when combined with air moisture, tiny droplets of hydrochloric acid are formed. It is a strong acid and reacts vigorously with most metals. However, metals such as gold, platinum, silver, tungsten and lead are practically not etched with hydrochloric acid. Many base metals dissolve in acid to form chlorides, such as zinc:
Zn + 2HCl \u003d ZnCl 2 + H 2
Pure acid is colorless, while technical acid has a yellowish tint caused by traces of compounds of iron, chlorine and other elements (FeCl3). Often a dilute acid containing 10% or less hydrogen chloride is used. Diluted solutions do not emit gaseous HCl and do not smoke in either dry or humid air.
The use of hydrochloric acid
Hydrochloric acid is widely used in industry for extracting metals from ores, pickling metals, etc. It is also used in the manufacture of soldering fluid, in the deposition of silver, and as an integral part of aqua regia.
The scale of the use of hydrochloric acid in industry is less than that of nitric acid. This is due to the fact that hydrochloric acid causes corrosion of steel equipment. In addition, its volatile vapors are quite harmful and also cause corrosion of metal products. This must be taken into account when storing hydrochloric acid. Hydrochloric acid is stored and transported in rubber-lined tanks and barrels, i.e. in vessels, the inner surface of which is covered with acid-resistant rubber, as well as in glass bottles and polyethylene utensils.
Hydrochloric acid is used to produce chlorides of zinc, manganese, iron and other metals, as well as ammonium chloride. Hydrochloric acid is used to clean the surfaces of metals, vessels, wells from carbonates, oxides and other sediments and contaminants. In this case, special additives are used - inhibitors that protect the metal from dissolution and corrosion, but do not delay the dissolution of oxides, carbonates and other similar compounds.
HCl is used in the industrial production of synthetic resins, rubbers. It is used as a raw material in the production of methyl chloride from methyl alcohol, ethyl chloride from ethylene, and vinyl chloride from acetylene.
Hydrochloric acid poisoning
HCl is poisonous. Poisoning usually occurs by mist formed when the gas interacts with water vapor in the air. HCl is also absorbed on the mucous membranes with the formation of acid, which causes severe irritation. With prolonged work in an HCl atmosphere, catarrhs of the respiratory tract, tooth decay, ulceration of the nasal mucosa, and gastrointestinal disorders are observed. Permissible content of HCl in the air of working premises is not more than 0.005 mg/l. For protection use a gas mask, goggles, rubber gloves, shoes, apron.
At the same time, our digestion is impossible without hydrochloric acid, its concentration in gastric juice is quite high. If the acidity in the body is lowered, then digestion is disturbed, and doctors prescribe such patients to take hydrochloric acid before eating.
The use of hydrochloric acid in everyday life
Concentrated "hodgepodge" is mixed with water in any proportion for domestic needs. A strong solution of this inorganic acid easily cleans earthenware plumbing from limescale and rust, while a weaker solution can remove rust stains, ink, and berry juice from fabrics.
If you look closely, the toilet duck cleaner says that it contains hydrochloric acid, so you need to work with it in rubber gloves and protect your eyes from splashing into them.
In addition, the life of no person is unthinkable without this acid - it is contained in the stomach and it is thanks to it that the food that has entered the stomach is dissolved (digested).
In addition, this acid serves as the first barrier against pathogenic bacteria that enter the stomach - they die in an acidic environment.
Well, people suffering from gastritis with high acidity, this acid is also well known. They even reduce its effect so that it does not destroy the walls of the stomach, with the help of special drugs that interact with it and reduce its concentration.
The most popular are preparations containing magnesium and aluminum oxides, for example, Maalox. However, there are extreme people who drink baking soda, although it has already been proven that this only leads to temporary relief.
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 PropertiesIt 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
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) are formed. .
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. IN Lately the level of production of hydrochloric acid by 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 types of 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.
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
Structural formula
True, empirical, or gross formula: HCl
Chemical composition of hydrochloric acid
Molecular weight: 36.461
Hydrochloric acid(also hydrochloric, hydrochloric acid, hydrogen chloride) - a solution of hydrogen chloride (HCl) in water, a strong monobasic acid. Colorless, transparent, caustic liquid, "fuming" in air (technical hydrochloric acid is yellowish due to impurities of iron, chlorine, etc.). At a concentration of about 0.5%, it is present 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 are highly dependent on the concentration of dissolved hydrogen chloride. When solidified, it gives crystalline 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 standing in a series of electrochemical potentials up to hydrogen, with the formation of a salt and the release of gaseous hydrogen.
- Interaction with metal oxides to form a soluble salt and water.
- Interaction with metal hydroxides to form a soluble salt and water (neutralization reaction).
- Interaction with metal salts formed by weaker acids, such as carbonic.
- Interaction with strong oxidizing agents (potassium permanganate, manganese dioxide) with the release of gaseous chlorine.
- Interaction with ammonia with the formation of thick white smoke, consisting of the smallest crystals of ammonium chloride.
- A qualitative reaction to hydrochloric acid and its salts is its interaction with silver nitrate, which forms a curd precipitate of silver chloride, insoluble in nitric acid.
Receipt
Hydrochloric acid is produced by dissolving hydrogen chloride gas in water. Hydrogen chloride is obtained by burning hydrogen in chlorine, the acid obtained in this way is called synthetic. Hydrochloric acid is also obtained from off-gases - by-product gases generated during various processes, for example, during the chlorination of hydrocarbons. The hydrogen chloride contained in these gases is called off-gas, and the acid thus obtained is called off-gas. In recent decades, the share of off-gas hydrochloric acid in the volume of production has been gradually increasing, displacing the acid obtained 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 in the action of concentrated sulfuric acid on table salt. At temperatures above 550 °C and an excess of table salt, interaction is possible. It is possible to obtain by hydrolysis of chlorides of magnesium, aluminum (hydrated salt is heated). These reactions may not go to completion with the formation of basic chlorides (oxychlorides) of variable composition, for example. Hydrogen chloride is highly soluble in water. So, 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 36% hydrochloric acid is usually used in practice.
Application
Industry
- It is used in hydrometallurgy and electroforming (etching, pickling), for cleaning the surface of metals during soldering and tinning, for obtaining 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 needed here) from contamination and disinfection.
- It is registered in the food industry as an acidity regulator (food additive E507). It is used to make seltzer (soda) water.
Medicine
- A natural component of human gastric juice. At a concentration of 0.3-0.5%, usually mixed with the enzyme pepsin, it is administered orally with insufficient acidity.
Features of circulation
Highly concentrated hydrochloric acid is a corrosive substance that causes severe chemical burns if it comes into contact with the skin. Eye contact is especially dangerous. To neutralize burns, a weak alkali solution, usually baking soda, is used. When opening vessels with concentrated hydrochloric acid, hydrogen chloride vapor, attracting moisture from the air, forms a mist that irritates the eyes and respiratory tract of a person. Reacts with strong oxidizing agents (chlorine, manganese dioxide, potassium permanganate) to form toxic chlorine gas. In the Russian Federation, the circulation of hydrochloric acid with a concentration of 15% or more is limited.
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 PropertiesIt 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
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) are formed. .
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 types of 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.
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
It is a proven fact that hydrochloric acid interacts with active metals. At the same time, some substances are able to react to such a compound, while the other part remains intact.
Inactive metals cannot react to a substance: they include gold, silver, mercury.
Hydrochloric acid is a compound of chlorine and hydrogen. By dissolving a gaseous substance called hydrogen chloride in water, this compound is obtained.
Hydrogen ions in this equation play the role of an oxidizing agent, which causes a reaction in active metals.
At the entrance exams in chemistry, you can often find a task to determine substances that can react to hydrochloric acid.
In addition, the task "make an equation" often causes fear in the eyes of graduates.
In order not to be confused with chemical problems, it is recommended to study in more detail the information on the interaction with this compound.
All existing substances can be divided into metals that displace hydrogen from the compound, do not displace hydrogen, as well as active and inactive metals.
The following substances react with hydrochloric acid:
- Chemical bases. Hydrochloric acid can neutralize bases. As you know, they consist of a metal atom, which is affected by acid.
These include sodium hydroxide, barium, aluminum. The neutralization reaction gives the formation of salt and water.
- Metals. If we turn to the electrochemical series, we can see that hydrochloric acid reacts with all elements up to hydrogen in this series.
These include sodium, magnesium, aluminum, lithium, barium, calcium, zinc, iron and other elements. When interacting, they form chlorides and release hydrogen gas.
- Basic and atmospheric oxides. During the reaction, soluble salts and water are formed. HCl interacts with aluminum oxide, copper, zinc, sodium.
- Carbonates. When interacting with calcium carbonates, the following equation will be obtained: CaCO₃ + 2HCl → CaCl₂ + CO₂ + H₂O.
It follows from this that it stands out carbon dioxide, as well as water and carbonic acid.
- Strong oxidizers. If the substance interacts with potassium permanganate or manganese dioxide, the output is the release of gaseous chlorine.
- Ammonia. This interaction is marked by the release of strong smoke, so it is recommended to open all windows at the time of the experiments. Then ammonium chloride is released.
In addition to the listed substances and compounds, HCl is also capable of reacting with silver nitrate - during this interaction, a white precipitate of a cheesy type is formed.
Sign of interaction with zinc, iron and other metals
If the school chemistry course was successfully forgotten, you can recall what are the signs of the interaction of metals that react with hydrochloric acid.
So that experimental experiments do not cause an accident, it is recommended to open all windows in advance, arm yourself with protective clothing so that the skin of the hands is closed.
Note! Below we will talk about what signs indicate the reaction of elements with a compound.
In order not to conduct visual experiments, you can use theoretical information.
Consider what happens if you add a little acid to a certain type of metal:
| Metal | Sign of interaction |
| Zinc | If this silver-colored metal is lowered into a test tube with the indicated substance, one can gradually observe the release of a small amount of bubbles and hydrogen. The result is zinc chloride ZnCl₂ |
| Iron | During this interaction, ferric chloride is formed. The reaction is slow, however, if the tube is heated, the process will go faster. |
| Lithium | During the reaction, lithium chloride 2LiCl is formed, hydrogen is released. Small bubbles can be seen on the surface of this alkali metal. |
| Silicon | As a result of such a compound, a complex component called chlorosilane appears. Hydrogen gas is also released. Such a reaction occurs when heated to 350 degrees, and copper acts as a catalyst. |
| Magnesium | With such an interaction, heat is released, the metal begins to melt |
How to write a reaction equation
One of the most common tasks in exams and tests is to write an equation for the reaction of HCl, in this case, hydrochloric acid, with other substances or compounds.
In order not to get confused in the decision, we offer a few tips and cheat sheets for easy memorization:
- Remember the letter designation of this substance - hydrochloric acid in chemistry is denoted as HCl: if the substance is diluted, this is indicated in brackets next to it.
- As mentioned above, the substance is able to react with active metals that are up to hydrogen in the electrochemical series; in addition, it reacts with bases, oxides, hydroxides and carbonates.
- Chemical bases are designated as OH, oxides - O, hydroxides - OH2, carbonates - CO3.
- The reaction equation will always have a + sign, because in the process of interaction several components are combined.
- HCl can go as the first or second term, after the addition of the metal, the substance goes with the = sign, after which the reaction is described, where the decomposition products are indicated.
- For example, when sulfuric acid reacts with magnesium sulfate, the following equation is obtained: Mg + H2SO4 \u003d MgSO4 + H2.
- Hydrochloric acid and barium hydroxide give the following equation: 2HCl + Ba(OH)2 = BaCl2 + 2H2O.
- In the reaction of the combination of hydrogen, chlorine and chalk, calcium chloride is formed: CaCO3 + 2HCl \u003d CaCl2 + CO2 + H2O.
- A solution of sodium carbonate with acid looks like this: HCl + Na2CO3 \u003d 2NaCl + H2O + CO2.
It is not difficult to make an equation, it is important to initially correctly designate the letter symbols of each element or substance.