Hydrochloric acid concentrated how many percent. Hydrochloric acid

Hydrochloric acid does not belong to those substances from which it is possible to prepare a solution of exactly concentration by sample. Therefore, an acid solution of approximate concentration is first prepared, and the exact concentration is established by titration with Na 2 CO 3 or Na 2 B 4 O 7 .10H 2 O.

1. Preparation of hydrochloric acid solution

According to the formula C (HCl) \u003d

the mass of hydrogen chloride required to prepare 1 liter of an acid solution with a molar equivalent concentration of 0.1 mol/l is calculated.

m(HCl) = C(HCl) . Me(HCl) .V(solution),

where Me(HCl) = 36.5 g/mol;

m(HCl) = 0.1. 36.5. 1 = 3.65 g

Since a solution of hydrochloric acid is prepared from concentrated, it is necessary to measure its density using a hydrometer and find from the reference book what percentage of acid of such density corresponds. For example, density (r) = 1.19 g / ml, w = 37%, then

m(p-ra) = G;

V (solution) \u003d m (solution) / r \u003d 9.85 / 1.19 \u003d 8 ml.

Thus, to prepare 1 liter of HCl solution, C(HCl) = 0.1 mol/l, measure about 8 ml of hydrochloric acid (r = 1.19 g/ml) using a cylinder (volume 10–25 ml) or a graduated tube ), transfer it to a flask with distilled water and bring the solution to the mark. The HCl solution thus prepared has an approximate concentration (> 0.1 mol/l).

2. Preparation of standard sodium carbonate solution

A weighed amount of sodium carbonate is calculated, which is necessary to prepare 100.0 ml of a solution with a molar equivalent concentration of 0.1 mol/l.

m (Na 2 CO 3) \u003d C e (Na 2 CO 3) . Me (Na 2 CO 3). V (solution),

where Me (Na 2 CO 3) \u003d M (Na 2 CO 3) / 2 \u003d 106/2 \u003d 53 g / mol;

m (Na 2 CO 3) \u003d 0.1.53.0.1 \u003d 0.53 g.

Previously, 0.5–0.6 g of Na 2 CO 3 is weighed on a technical scale. The sample is transferred to a watch glass, previously weighed on an analytical balance, and the glass with the sample is accurately weighed. Transfer the sample through a funnel into a 100 ml volumetric flask, add to approximately 2/3 of the volume of distilled water. The contents of the flask are stirred with careful rotational movements until the sample is completely dissolved, after which the solution is brought to the mark.

3.Standardization of hydrochloric acid solution

To establish the exact concentration of hydrochloric acid, a prepared Na 2 CO 3 solution of the exact concentration is used. An aqueous solution of sodium carbonate due to hydrolysis has an alkaline reaction of the medium:

Na 2 CO 3 + 2H 2 O \u003d 2NaOH + H 2 CO 3 (hydrolysis reaction);

2NaOH + 2HCl = 2NaCl + 2H 2 O;

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Na 2 CO 3 + 2HCl = 2NaCl + H 2 CO 3 (titration reaction).

It can be seen from the overall equation that as a result of the reaction, weak carbonic acid accumulates in the solution, which determines the pH at the equivalence point:

pH \u003d 1/2 pK 1 (H2CO3) - 1/2 lgС (H2CO3) \u003d 1/2.6.35 - 1/2lg 0.1 \u003d 3.675.

Methyl orange is best for titration.

Rinse the burette with the prepared HCl solution and fill it almost to the top with hydrochloric acid solution. Then, substituting a glass under the burette and opening the clamp, fill the lower end of the burette so that no air bubbles remain in it, the lower meniscus of the HCl solution in the burette should be at zero division. When counting on the burette (and pipette), the eye should be at the level of the meniscus.

Definition progress. 10.00 ml of the prepared Na 2 CO 3 solution is taken into the flask for titration with a pipette, 1–2 drops of methyl orange are added and titrated with HCl solution until the color changes from yellow to orange-pink. The experiment is repeated several times, the results are entered in table 4, the average volume of hydrochloric acid is found and its molar concentration of the equivalent, titer and titer for the analyte are calculated.

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 fog in the presence of moisture), it also has other names: hydrochloric acid, and according to Ukrainian nomenclature - chloride acid. The chemical formula can be represented as follows: 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, and also 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, hydrochloric acid has reducing properties: in concentrated form, it 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%.

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 the dry state, hydrogen chloride gas is quite inert, but it can already interact with some organic substances, such as 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 \u003d HCl - the reaction occurs at an 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 a 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

Chemical properties

Hydrochloric acid, hydrogen chloride or hydrochloric acid - solution Hcl in water. According to Wikipedia, the substance belongs to the group of inorganic strong monobasic to-t. The full name of the compound in Latin: hydrochloric acid.

Formula of hydrochloric acid in chemistry: HCl. In a molecule, hydrogen atoms combine with halogen atoms - Cl. If we consider the electronic configuration of these molecules, it can be noted that the compounds take part in the formation of molecular orbitals 1s-hydrogen orbitals and both 3s and 3p-orbitals of an atom Cl. In the chemical formula of hydrochloric acid 1s-, 3s- and 3r-atomic orbitals overlap and form 1, 2, 3 orbitals. Wherein 3s-orbital is not binding. There is a shift of the electron density to the atom Cl and the polarity of the molecule decreases, but the binding energy of molecular orbitals increases (if we consider it along with other hydrogen halides ).

Physical properties of hydrogen chloride. It is a clear, colorless liquid that smokes when exposed to air. Molar mass of a chemical compound = 36.6 grams per mole. Under standard conditions, at an air temperature of 20 degrees Celsius, the maximum concentration of a substance is 38% by weight. The density of concentrated hydrochloric acid in this kind of solution is 1.19 g/cm³. In general, physical properties and characteristics such as density, molarity, viscosity, heat capacity, boiling point and pH, strongly depend on the concentration of the solution. These values ​​are discussed in more detail in the table of densities. For example, the density of Hydrochloric Acid 10% = 1.048 kg per liter. When solidified, the substance forms crystalline hydrates different compositions.

Chemical properties of hydrochloric acid. What does hydrochloric acid react with? The substance interacts with metals that stand in front of hydrogen in a series of electrochemical potentials (iron, magnesium, zinc, and others). In this case, salts are formed and gaseous H. Lead, copper, gold, silver and other metals to the right of hydrogen do not react with hydrochloric acid. The substance reacts with metal oxides producing water and a soluble salt. Sodium hydroxide under the action of to-you forms and water. The neutralization reaction is characteristic of this compound.

Dilute Hydrochloric Acid reacts with metal salts, which are formed by weaker acids. For example, propionic acid weaker than salt. The substance does not react with stronger acids. and sodium carbonate will form after reaction with HCl chloride, carbon monoxide and water.

For a chemical compound, reactions with strong oxidizing agents are characteristic, with manganese dioxide , potassium permanganate : 2KMnO4 + 16HCl = 5Cl2 + 2MnCl2 + 2KCl + 8H2O. The substance reacts with ammonia , which produces thick white smoke, which consists of very fine crystals of ammonium chloride. The mineral pyrolusite also reacts with hydrochloric acid, as it contains manganese dioxide : MnO2+4HCl=Cl2+MnO2+2H2O(oxidation reaction).

There is a qualitative reaction to hydrochloric acid and its salts. When a substance interacts with silver nitrate a white precipitate silver chloride and formed nitric acid . Interaction reaction equation methylamine with hydrogen chloride looks like this: HCl + CH3NH2 = (CH3NH3)Cl.

A substance reacts with a weak base aniline . After dissolving aniline in water, hydrochloric acid is added to the mixture. As a result, the base dissolves and forms aniline hydrochloride (phenylammonium chloride ): (С6Н5NH3)Cl. The reaction of interaction of aluminum carbide with hydrochloric acid: Al4C3+12HCL=3CH4+4AlCl3. Reaction equation potassium carbonate with which it looks like this: K2CO3 + 2HCl = 2KCl + H2O + CO2.

Getting hydrochloric acid

To obtain synthetic hydrochloric acid, hydrogen is burned in chlorine, and then the resulting gaseous hydrogen chloride is dissolved in water. It is also common to produce a reagent from off-gases, which are formed as by-products during the chlorination of hydrocarbons (off-gas Hydrochloric Acid). In the production of this chemical compound, GOST 3118 77- for reagents and GOST 857 95– for technical synthetic hydrochloric acid.

In the laboratory, you can use a long-standing method in which table salt is exposed to concentrated sulfuric acid. Also, the agent can be obtained using the hydrolysis reaction aluminum chloride or magnesium . During the reaction, oxychlorides variable composition. To determine the concentration of a substance, standard titers are used, which are available in sealed ampoules, so that later it is possible to obtain a standard solution of a known concentration and use it to determine the quality of another titrant.

The substance has a fairly wide scope:

• it is used in hydrometallurgy, pickling and pickling;
• when cleaning metals during tinning and soldering;
• as a reagent for obtaining manganese chloride , zinc, iron and other metals;
• in the manufacture of mixtures with surfactants for cleaning metal and ceramic products from infection and dirt (inhibited hydrochloric acid is used);
• as an acidity regulator E507 in the food industry, as part of soda water;
• in medicine with insufficient acidity of gastric juice.

This chemical compound has a high hazard class - 2 (according to GOST 12L.005). When working with acid, special skin and eye protection. Sufficiently caustic substance in contact with the skin or inhalation causes chemical burns. To neutralize it, alkali solutions are used, most often baking soda. Hydrogen chloride vapor forms a caustic mist with water molecules in the air, which irritates the respiratory tract and eyes. If the substance reacts with bleach, potassium permanganate and other oxidizing agents, then a toxic gas, chlorine, is formed. On the territory of the Russian Federation, the circulation of Hydrochloric Acid with a concentration of more than 15% is limited.

pharmachologic effect

Increases the acidity of gastric juice.

Pharmacodynamics and pharmacokinetics

What is gastric acidity? This is a characteristic of the concentration of hydrochloric acid in the stomach. Acidity is expressed in pH. Normally, acid should be produced in the composition of gastric juice and take an active part in the processes of digestion. Formula of hydrochloric acid: HCl. It is produced by parietal cells located in the fundic glands, with the participation of H+/K+-ATPase . These cells line the fundus and body of the stomach. The acidity of gastric juice itself is variable and depends on the number of parietal cells and the intensity of the processes of neutralization of the substance by the alkaline components of gastric juice. Concentration produced to - you are stable and equal to 160 mmol/l. A healthy person should normally produce no more than 7 and at least 5 mmol of a substance per hour.

With insufficient or excessive production of Hydrochloric Acid, diseases of the digestive tract occur, the ability to absorb certain microelements, such as iron, deteriorates. The drug stimulates the secretion of gastric juice, reduces pH. Activates pepsinogen , converts it into an active enzyme pepsin . The substance has a beneficial effect on the acid reflex of the stomach, slows down the transition of incompletely digested food into the intestines. The processes of fermentation of the contents of the digestive tract slow down, pain and belching disappear, iron is better absorbed.

After oral administration, the drug is partially metabolized by saliva and gastric mucus, the contents of the duodenum 12. The unbound substance penetrates into the duodenum, where it is completely neutralized by its alkaline contents.

Indications for use

The substance is part of synthetic detergents, a concentrate for rinsing the oral cavity for the care of contact lenses. Diluted Hydrochloric Acid is prescribed for diseases of the stomach, accompanied by low acidity, with hypochromic anemia in combination with iron preparations.

Contraindications

The medicine should not be used for allergies on a synthetic substance, with diseases of the digestive tract associated with high acidity, with.

Side effects

Concentrated Hydrochloric Acid can cause severe burns if it comes into contact with the skin, eyes or respiratory tract. As part of various lek. preparations use a diluted substance, with prolonged use of large dosages, a deterioration in the condition of tooth enamel may occur.

Instructions for use (Method and dosage)

Hydrochloric acid is used in accordance with the instructions.

Inside the medicine is prescribed, previously dissolved in water. Usually use 10-15 drops of the drug in half a glass of liquid. The medicine is taken with meals, 2-4 times a day. The maximum single dosage is 2 ml (about 40 drops). Daily dose - 6 ml (120 drops).

Overdose

Cases of overdose are not described. With uncontrolled intake of the substance inside in large quantities, ulcers and erosions occur in the digestive tract. You should seek help from a doctor.

Interaction

The substance is often used in combination with pepsin and other medicines. drugs. The chemical compound in the digestive tract interacts with bases and some substances (see chemical properties).

special instructions

When treating with hydrochloric acid preparations, it is necessary to strictly adhere to the recommendations in the instructions.

Preparations containing (Analogues)

Coincidence in the ATX code of the 4th level:

For industrial purposes, inhibited hydrochloric acid (22-25%) is used. For medical purposes, the solution is used: Hydrochloric acid diluted . The substance is also contained in a concentrate for rinsing the mouth. Parontal , in soft contact lens care solution Biotru .

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.

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

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:

1. Effect of saturated sulfuric acid on sodium chloride at 150°C.
2. The interaction of the above substances under conditions with a temperature of 550 ° C and above.
3. 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