Sulfurous acid and its salts. Sulfuric acid

Sulfuric acid (H2SO4) is one of the most caustic acids and dangerous reagents, known to man especially in concentrated form. Chemically pure sulfuric acid is a heavy toxic liquid of oily consistency, odorless and colorless. It is obtained by the oxidation of sulfur dioxide (SO2) by the contact method.

At a temperature of + 10.5 ° C, sulfuric acid turns into a frozen glassy crystalline mass, greedily, like a sponge, absorbing moisture from environment. In industry and chemistry, sulfuric acid is one of the main chemical compounds and occupies a leading position in terms of production in tons. That is why sulfuric acid is called the "blood of chemistry". With the help of sulfuric acid, fertilizers, medicines, other acids, large fertilizers, and much more are obtained.

Basic physical and chemical properties of sulfuric acid

1. Sulfuric acid in pure form(formula H2SO4), at a concentration of 100% is a colorless thick liquid. The most important property of H2SO4 is its high hygroscopicity - the ability to remove water from the air. This process is accompanied by a massive release of heat.
2. H2SO4 is a strong acid.
3. Sulfuric acid is called monohydrate - it contains 1 mol of H2O (water) per 1 mol of SO3. Because of its impressive hygroscopic properties, it is used to extract moisture from gases.
4. Boiling point - 330 ° C. In this case, the acid is decomposed into SO3 and water. Density - 1.84. Melting point - 10.3 ° C /.
5. Concentrated sulfuric acid is a powerful oxidizing agent. To start the redox reaction, the acid must be heated. The result of the reaction is SO2. S+2H2SO4=3SO2+2H2O
6. Depending on the concentration, sulfuric acid reacts differently with metals. In a dilute state, sulfuric acid is capable of oxidizing all metals that are in the series of voltages to hydrogen. An exception is made as the most resistant to oxidation. Dilute sulfuric acid reacts with salts, bases, amphoteric and basic oxides. Concentrated sulfuric acid is capable of oxidizing all metals in the series of voltages, and silver too.
7. Sulfuric acid forms two types of salts: acidic (hydrosulfates) and medium (sulfates)
8. H2SO4 enters into an active reaction with organic substances and non-metals, and it can turn some of them into coal.
9. Sulfuric anhydrite is perfectly soluble in H2SO4, and in this case oleum is formed - a solution of SO3 in sulfuric acid. Outwardly, it looks like this: fuming sulfuric acid, releasing sulfuric anhydrite.
10. Sulfuric acid in aqueous solutions is a strong dibasic acid, and when it is added to water, a huge amount of heat is released. When preparing dilute solutions of H2SO4 from concentrated ones, it is necessary to add a heavier acid to water in a small stream, and not vice versa. This is done to avoid boiling water and splashing acid.

Concentrated and dilute sulfuric acids

Concentrated solutions of sulfuric acid include solutions from 40%, capable of dissolving silver or palladium.

Dilute sulfuric acid includes solutions whose concentration is less than 40%. These are not such active solutions, but they are able to react with brass and copper.

Getting sulfuric acid

The production of sulfuric acid on an industrial scale was launched in the 15th century, but at that time it was called "vitriol". If earlier humanity consumed only a few tens of liters of sulfuric acid, then in modern world the calculation goes to millions of tons per year.

The production of sulfuric acid is carried out industrially, and there are three of them:

1. contact method.
2. nitrous method
3. Other Methods

Let's talk in detail about each of them.

contact production method

The contact method of production is the most common, and it performs the following tasks:

• It turns out a product that satisfies the needs of the maximum number of consumers.
• During production, harm to the environment is reduced.

In the contact method, the following substances are used as raw materials:

• pyrite (sulfur pyrites);
• sulfur;
• vanadium oxide (this substance causes the role of a catalyst);
• hydrogen sulfide;
• sulfides of various metals.

Before starting the production process, raw materials are pre-prepared. To begin with, in special crushing plants, pyrite is subjected to grinding, which allows, due to an increase in the contact area active substances, speed up the reaction. Pyrite undergoes purification: it is lowered into large containers of water, during which waste rock and all kinds of impurities float to the surface. They are removed at the end of the process.

The production part is divided into several stages:

1. After crushing, pyrite is cleaned and sent to the furnace - where it is fired at temperatures up to 800 ° C. According to the principle of counterflow, air is supplied to the chamber from below, and this ensures that the pyrite is in a suspended state. Today, this process takes a few seconds, but earlier it took several hours to fire. During the roasting process, wastes appear in the form of iron oxide, which are removed and subsequently transferred to the enterprises of the metallurgical industry. During firing, water vapor, O2 and SO2 gases are released. When the purification from water vapor and the smallest impurities is completed, pure sulfur oxide and oxygen are obtained.
2. In the second stage, an exothermic reaction takes place under pressure using a vanadium catalyst. The start of the reaction starts when the temperature reaches 420 °C, but it can be increased to 550 °C in order to increase efficiency. During the reaction, catalytic oxidation occurs and SO2 becomes SO3.
3. The essence of the third stage of production is as follows: the absorption of SO3 in the absorption tower, during which the oleum H2SO4 is formed. In this form, H2SO4 is poured into special containers (it does not react with steel) and is ready to meet the end user.

During production, as we said above, a lot of thermal energy is generated, which is used for heating purposes. Many sulfuric acid plants install steam turbines that use the exhaust steam to generate additional electricity.

Nitrous process for the production of sulfuric acid

Despite the advantages of the contact method of production, which produces more concentrated and pure sulfuric acid and oleum, quite a lot of H2SO4 is produced by the nitrous method. In particular, at superphosphate plants.

For the production of H2SO4, sulfur dioxide acts as the initial substance, both in the contact and in the nitrous method. It is obtained specifically for these purposes by burning sulfur or roasting sulfurous metals.

The conversion of sulfur dioxide into sulfurous acid consists in the oxidation of sulfur dioxide and the addition of water. The formula looks like this:
SO2 + 1|2 O2 + H2O = H2SO4

But sulfur dioxide does not directly react with oxygen, therefore, with the nitrous method, the oxidation of sulfur dioxide is carried out using nitrogen oxides. Higher oxides of nitrogen (we are talking about nitrogen dioxide NO2, nitrogen trioxide NO3) at this process are reduced to nitric oxide NO, which is subsequently again oxidized by oxygen to higher oxides.

The production of sulfuric acid by the nitrous method is technically formalized in two ways:

• Chamber.
• Tower.

The nitrous method has a number of advantages and disadvantages.

Disadvantages of the nitrous method:

• It turns out 75% sulfuric acid.
• Product quality is low.
• Incomplete return of nitrogen oxides (addition of HNO3). Their emissions are harmful.
• The acid contains iron, nitrogen oxides and other impurities.

Advantages of the nitrous method:

• The cost of the process is lower.
• The possibility of processing SO2 at 100%.
• Simplicity of hardware design.

Major Russian Sulfuric Acid Plants

The annual production of H2SO4 in our country is calculated in six figures - about 10 million tons. The leading producers of sulfuric acid in Russia are companies that are, in addition, its main consumers. We are talking about companies whose field of activity is the production of mineral fertilizers. For example, "Balakovo mineral fertilizers", "Ammophos".

In the Crimea, in Armyansk, the largest producer of titanium dioxide operates in the territory of Eastern Europe Crimean Titan. In addition, the plant is engaged in the production of sulfuric acid, mineral fertilizers, iron sulphate, etc.

sulfuric acid various kinds produced by many factories. For example, battery sulfuric acid is produced by: Karabashmed, FKP Biysk Oleum Plant, Svyatogor, Slavia, Severkhimprom, etc.

Oleum is produced by UCC Shchekinoazot, FKP Biysk Oleum Plant, Ural Mining and Metallurgical Company, Kirishinefteorgsintez Production Association, etc.

Sulfuric acid of high purity is produced by UCC Shchekinoazot, Component-Reaktiv.

Spent sulfuric acid can be bought at the plants ZSS, HaloPolymer Kirovo-Chepetsk.

Manufacturers of technical sulfuric acid are Promsintez, Khiprom, Svyatogor, Apatit, Karabashmed, Slavia, Lukoil-Permnefteorgsintez, Chelyabinsk Zinc Plant, Electrozinc, etc.

Due to the fact that pyrite is the main raw material in the production of H2SO4, and this is a waste product of enrichment enterprises, its suppliers are the Norilsk and Talnakh enrichment plants.

The leading world positions in the production of H2SO4 are occupied by the USA and China, which account for 30 million tons and 60 million tons, respectively.

Scope of sulfuric acid

About 200 million tons of H2SO4 are consumed annually in the world, from which wide range products. Sulfuric acid rightfully holds the palm among other acids in terms of industrial use.

As you already know, sulfuric acid is one of the most important products of the chemical industry, so the scope of sulfuric acid is quite wide. The main uses of H2SO4 are as follows:

• Sulfuric acid is used in huge volumes for the production of mineral fertilizers, and it takes about 40% of the total tonnage. For this reason, plants producing H2SO4 are being built next to fertilizer plants. These are ammonium sulfate, superphosphate, etc. In their production, sulfuric acid is taken in its pure form (100% concentration). It will take 600 liters of H2SO4 to produce a ton of ammophos or superphosphate. It is these fertilizers that are most often used in agriculture.
• H2SO4 is used to make explosives.
• Purification of petroleum products. To obtain kerosene, gasoline, mineral oils, hydrocarbon purification is required, which occurs with the use of sulfuric acid. In the process of refining oil for the purification of hydrocarbons, this industry "takes" as much as 30% of the world's tonnage of H2SO4. In addition, the octane number of fuel is increased with sulfuric acid and wells are treated during oil production.
• in the metallurgical industry. Sulfuric acid is used in metallurgy to remove scale and rust from wire, sheet metal, as well as to reduce aluminum in the production of non-ferrous metals. Before coating metal surfaces with copper, chromium or nickel, the surface is etched with sulfuric acid.
• In the manufacture of medicines.
• in the production of paints.
• in the chemical industry. H2SO4 is used in the production detergents, ethyl agent, insecticides, etc., and these processes are impossible without it.
• To receive others known acids, organic and inorganic compounds used for industrial purposes.

Sulfuric acid salts and their uses

The most important salts of sulfuric acid are:

• Glauber's salt Na2SO4 10H2O (crystalline sodium sulfate). The scope of its application is quite capacious: the production of glass, soda, in veterinary medicine and medicine.
• Barium sulfate BaSO4 is used in the production of rubber, paper, white mineral paint. In addition, it is indispensable in medicine for fluoroscopy of the stomach. It is used to make "barium porridge" for this procedure.
• Calcium sulfate CaSO4. In nature, it can be found in the form of gypsum CaSO4 2H2O and anhydrite CaSO4. Gypsum CaSO4 2H2O and calcium sulfate are used in medicine and construction. With gypsum, when heated to a temperature of 150 - 170 ° C, partial dehydration occurs, as a result of which burnt gypsum, known to us as alabaster, is obtained. Kneading alabaster with water to the consistency of batter, the mass quickly hardens and turns into a kind of stone. It is this property of alabaster that is actively used in construction work: casts and molds are made from it. In plastering work, alabaster is indispensable as a binder. Patients of trauma departments are given special fixing solid bandages - they are made on the basis of alabaster.
• Ferrous vitriol FeSO4 7H2O is used for the preparation of ink, impregnation of wood, and also in agricultural activities for the destruction of pests.
• Alum KCr(SO4)2 12H2O, KAl(SO4)2 12H2O, etc. are used in the production of paints and the leather industry (tanning).
• Many of you know copper sulfate CuSO4 5H2O firsthand. It is an active assistant in agriculture in the fight against plant diseases and pests - an aqueous solution of CuSO4 5H2O is used to pickle grain and spray plants. It is also used to prepare some mineral paints. And in everyday life it is used to remove mold from the walls.
• Aluminum sulfate - it is used in the pulp and paper industry.

Sulfuric acid in dilute form is used as an electrolyte in lead-acid batteries. In addition, it is used to produce detergents and fertilizers. But in most cases, it comes in the form of oleum - this is a solution of SO3 in H2SO4 (other oleum formulas can also be found).

Amazing fact! Oleum is more reactive than concentrated sulfuric acid, but despite this, it does not react with steel! It is for this reason that it is easier to transport than sulfuric acid itself.

The sphere of use of the “queen of acids” is truly large-scale, and it is difficult to tell about all the ways in which it is used in industry. It is also used as an emulsifier in the food industry, for water treatment, in the synthesis of explosives, and for many other purposes.

History of sulfuric acid

Who among us has never heard of blue vitriol? So, it was studied in antiquity, and in some works the beginnings new era scientists discussed the origin of vitriol and their properties. Vitriol was studied by the Greek physician Dioscorides, the Roman explorer of nature Pliny the Elder, and in their writings they wrote about the ongoing experiments. AT medical purposes various vitriol substances were used by the ancient physician Ibn Sina. How vitriol was used in metallurgy, was said in the works of alchemists Ancient Greece Zosimas of Panopolis.

The first method of obtaining sulfuric acid is the process of heating potassium alum, and there is information about this in the alchemical literature of the XIII century. At that time, the composition of alum and the essence of the process were not known to alchemists, but already in the 15th century they began to engage in the chemical synthesis of sulfuric acid purposefully. The process was as follows: alchemists treated a mixture of sulfur and antimony (III) sulfide Sb2S3 by heating with nitric acid.

In medieval times in Europe, sulfuric acid was called "vitriol oil", but then the name changed to vitriol.

In the 17th century, Johann Glauber obtained sulfuric acid by burning potassium nitrate and native sulfur in the presence of water vapor. As a result of the oxidation of sulfur with nitrate, sulfur oxide was obtained, which reacted with water vapor, and as a result, an oily liquid was obtained. It was vitriol oil, and this name for sulfuric acid exists to this day.

The pharmacist from London, Ward Joshua, used this reaction for the industrial production of sulfuric acid in the thirties of the 18th century, but in the Middle Ages its consumption was limited to a few tens of kilograms. The scope of use was narrow: for alchemical experiments, purification of precious metals and in the pharmaceutical business. Concentrated sulfuric acid was used in small quantities in the manufacture of special matches that contained bertolet salt.

In Russia, vitriol appeared only in the 17th century.

In Birmingham, England, John Roebuck adapted the above method for producing sulfuric acid in 1746 and launched production. At the same time, he used strong large lead-lined chambers, which were cheaper than glass containers.

In industry, this method held positions for almost 200 years, and 65% sulfuric acid was obtained in the chambers.

After a while, the English Glover and the French chemist Gay-Lussac improved the process itself, and sulfuric acid began to be obtained with a concentration of 78%. But such an acid was not suitable for the production, for example, of dyes.

In the early 19th century, new methods were discovered for oxidizing sulfur dioxide to sulfuric anhydride.

Initially, this was done using nitrogen oxides, and then platinum was used as a catalyst. These two methods of oxidizing sulfur dioxide have further improved. The oxidation of sulfur dioxide on platinum and other catalysts became known as the contact method. And the oxidation of this gas with nitrogen oxides was called the nitrous method for producing sulfuric acid.

British merchant acetic acid It was only in 1831 that Peregrine Philips patented an economical process for the production of sulfur oxide (VI) and concentrated sulfuric acid, and it is he who is today known to the world as a contact method for obtaining it.

The production of superphosphate began in 1864.

In the eighties of the nineteenth century in Europe, the production of sulfuric acid reached 1 million tons. The main producers were Germany and England, producing 72% of the total volume of sulfuric acid in the world.

Transportation of sulfuric acid is a labor-intensive and responsible undertaking.

Sulfuric acid belongs to the class of hazardous chemicals, and upon contact with the skin causes severe burns. In addition, it can cause chemical poisoning of a person. If during transportation are not observed certain rules, then sulfuric acid, due to its explosiveness, can cause a lot of harm to both people and the environment.

Sulfuric acid has been assigned a hazard class 8 and transportation must be carried out by specially trained and trained professionals. An important condition for the delivery of sulfuric acid is compliance with specially developed Rules for the transport of dangerous goods.

Shipping by car carried out according to the following rules:

1. For transportation, special containers are made of a special steel alloy that does not react with sulfuric acid or titanium. Such containers do not oxidize. Hazardous sulfuric acid is transported in special sulfuric acid chemical tanks. They differ in design and are selected during transportation depending on the type of sulfuric acid.
2. When transporting fuming acid, specialized isothermal thermos tanks are taken, in which the necessary temperature regime is maintained to preserve the chemical properties of the acid.
3. If ordinary acid is being transported, then a sulfuric acid tank is selected.
4. Transportation of sulfuric acid by road, such as fuming, anhydrous, concentrated, for batteries, glover, is carried out in special containers: tanks, barrels, containers.
5. By carriage dangerous goods only drivers who have an ADR certificate in their hands can do it.
6. Travel time has no restrictions, since during transportation it is necessary to strictly adhere to the permissible speed.
7. During transportation, a special route is built, which should run, bypassing crowded places and production facilities.
8. Transport must have special markings and danger signs.

Dangerous properties of sulfuric acid for humans

Sulfuric acid poses an increased danger to the human body. Its toxic effect occurs not only by direct contact with the skin, but by inhalation of its vapors, when sulfur dioxide is released. The hazard applies to:

• respiratory system;
• Integuments;
• Mucous membranes.

Intoxication of the body can be enhanced by arsenic, which is often part of sulfuric acid.

Important! As you know, when acid comes into contact with the skin, severe burns occur. No less dangerous is poisoning with sulfuric acid vapors. safe dose the content of sulfuric acid in the air is only 0.3 mg per 1 square meter.

If sulfuric acid gets on the mucous membranes or on the skin, a severe burn appears, which does not heal well. If the burn is impressive in scale, the victim develops a burn disease, which can even lead to death if qualified medical care is not provided in a timely manner.

Important! For an adult lethal dose sulfuric acid is only 0.18 cm per 1 liter.

Of course, "experience for yourself" the toxic effect of acid in ordinary life problematic. Most often, acid poisoning occurs due to neglect of industrial safety when working with a solution.

Mass poisoning with sulfuric acid vapor can occur due to technical problems in production or negligence, and a massive release into the atmosphere occurs. To prevent such situations, special services are working, the task of which is to control the functioning of production where hazardous acid is used.

What are the symptoms of sulfuric acid intoxication?

If the acid was ingested:

• Pain in the region of the digestive organs.
• Nausea and vomiting.
• Violation of the stool, as a result of severe intestinal disorders.
• Strong secretion of saliva.
• Because of toxic effects on the kidneys, the urine becomes reddish.
• Swelling of the larynx and throat. There are wheezing, hoarseness. This may lead to lethal outcome from suffocation.
• Brown spots appear on the gums.
• The skin turns blue.

With a burn skin there may be all the complications inherent in burn disease.

When poisoning in pairs, the following picture is observed:

• Burn of the mucous membrane of the eyes.
• Nose bleed.
• Burn of mucous membranes respiratory tract. In this case, the victim experiences a strong pain symptom.
• Swelling of the larynx with symptoms of suffocation (lack of oxygen, skin turns blue).
• If the poisoning is severe, then there may be nausea and vomiting.

It is important to know! Acid poisoning after ingestion is much more dangerous than intoxication from inhalation of vapors.

First aid and therapeutic procedures for damage by sulfuric acid

Proceed as follows when in contact with sulfuric acid:

• Call first ambulance. If the liquid got inside, then do a gastric lavage with warm water. After that, in small sips you will need to drink 100 grams of sunflower or olive oil. In addition, you should swallow a piece of ice, drink milk or burnt magnesia. This must be done to reduce the concentration of sulfuric acid and alleviate the human condition.
• If acid gets into the eyes, rinse them with running water, and then drip with a solution of dicaine and novocaine.
• If acid gets on the skin, the burned area should be washed well under running water and bandaged with soda. Rinse for about 10-15 minutes.
• In case of vapor poisoning, you need to go out into fresh air, and also rinse the affected mucous membranes with water as far as possible.

In a hospital setting, treatment will depend on the area of ​​the burn and the degree of poisoning. Anesthesia is carried out only with novocaine. In order to avoid the development of an infection in the affected area, a course of antibiotic therapy is selected for the patient.

At stomach bleeding plasma is injected or blood is transfused. The source of bleeding can be removed surgically.

1. Sulfuric acid in its pure 100% form is found in nature. For example, in Italy, Sicily in the Dead Sea, you can see a unique phenomenon - sulfuric acid seeps right from the bottom! And this is what happens: pyrite from earth's crust serves in this case as a raw material for its formation. This place is also called the Lake of Death, and even insects are afraid to fly up to it!
2. After major volcanic eruptions in earth's atmosphere drops of sulfuric acid can often be found, and in such cases the "culprit" can bring Negative consequences to the environment and cause serious climate change.
3. Sulfuric acid is an active water absorber, so it is used as a gas dryer. In the old days, in order to prevent windows from fogging up in the rooms, this acid was poured into jars and placed between the panes of window openings.
4. Sulfuric acid is the main cause of acid rain. main reason Acid rain is air pollution with sulfur dioxide, and when dissolved in water, it forms sulfuric acid. In turn, sulfur dioxide is emitted when fossil fuels are burned. In acid rain studied for last years, the content of nitric acid increased. The reason for this phenomenon is the reduction of sulfur dioxide emissions. Despite this fact, sulfuric acid remains the main cause of acid rain.

We offer you a video compilation interesting experiences with sulfuric acid.

Consider the reaction of sulfuric acid when it is poured into sugar. In the first seconds of sulfuric acid entering the flask with sugar, the mixture darkens. After a few seconds, the substance turns black. The most interesting thing happens next. The mass begins to grow rapidly and climb out of the flask. At the output, we get a proud substance, similar to porous charcoal, exceeding the original volume by 3-4 times.

The author of the video suggests comparing the reaction of Coca-Cola with hydrochloric acid and sulfuric acid. When mixing Coca-Cola with hydrochloric acid, no visual changes are observed, but when mixed with sulfuric acid, Coca-Cola begins to boil.

An interesting interaction can be observed when sulfuric acid gets on toilet paper. Toilet paper is made up of cellulose. When acid enters, cellulose molecules instantly break down with the release of free carbon. Similar charring can be observed when acid gets on the wood.

In a flask with concentrated acid I add a small piece of potassium. In the first second, smoke is released, after which the metal instantly flares up, lights up and explodes, cutting into pieces.

In the next experiment, when sulfuric acid hits a match, it flares up. In the second part of the experiment, aluminum foil is immersed with acetone and a match inside. There is an instantaneous heating of the foil with the release of a huge amount of smoke and its complete dissolution.

An interesting effect is observed when baking soda is added to sulfuric acid. Soda instantly turns into yellow. The reaction proceeds with rapid boiling and an increase in volume.

We categorically do not advise to carry out all the above experiments at home. Sulfuric acid is a very corrosive and toxic substance. Such experiments must be carried out in special rooms that are equipped with forced ventilation. The gases released in reactions with sulfuric acid are highly toxic and can cause damage to the respiratory tract and poison the body. In addition, similar experiments are carried out in the means personal protection skin and respiratory organs. Take care of yourself!

DEFINITION

anhydrous sulfuric acid is a heavy, viscous liquid that is easily miscible with water in any proportion: the interaction is characterized by an exceptionally large exothermic effect (~880 kJ / mol at infinite dilution) and can lead to explosive boiling and splashing of the mixture if water is added to the acid; That's why it's so important to always use reverse order in the preparation of solutions and add the acid to the water, slowly and with stirring.

Some physical properties of sulfuric acid are given in the table.

Anhydrous H 2 SO 4 is a wonderful compound with an unusually high permittivity and very high electrical conductivity, which is due to the ionic autodissociation (autoprotolysis) of the compound, as well as the relay-race conduction mechanism with proton transfer, which ensures the flow electric current through a viscous liquid with a large number of hydrogen bonds.

Table 1. Physical properties of sulfuric acid.

Getting sulfuric acid

Sulfuric acid is the most important industrial chemical and the cheapest bulk acid produced anywhere in the world.

Concentrated sulfuric acid (“vitriol oil”) was first obtained by heating “green vitriol” FeSO 4 × nH 2 O and spent in in large numbers to obtain Na 2 SO 4 and NaCl.

AT modern process For the production of sulfuric acid, a catalyst consisting of vanadium(V) oxide with the addition of potassium sulfate on a carrier of silicon dioxide or kieselguhr is used. Sulfur dioxide SO 2 is obtained by burning pure sulfur or by roasting sulfide ore (primarily pyrite or ores of Cu, Ni and Zn) in the process of extracting these metals. Then SO 2 is oxidized to trioxide, and then sulfuric acid is obtained by dissolving in water:

S + O 2 → SO 2 (ΔH 0 - 297 kJ / mol);

SO 2 + ½ O 2 → SO 3 (ΔH 0 - 9.8 kJ / mol);

SO 3 + H 2 O → H 2 SO 4 (ΔH 0 - 130 kJ / mol).

Chemical properties of sulfuric acid

Sulfuric acid is a strong dibasic acid. In the first stage, in solutions of low concentration, it dissociates almost completely:

H 2 SO 4 ↔H + + HSO 4 -.

Dissociation on the second stage

HSO 4 - ↔H + + SO 4 2-

proceeds to a lesser extent. The dissociation constant of sulfuric acid in the second stage, expressed in terms of ion activity, K 2 = 10 -2.

As a dibasic acid, sulfuric acid forms two series of salts: medium and acidic. Medium salts of sulfuric acid are called sulfates, and acid salts are called hydrosulfates.

Sulfuric acid greedily absorbs water vapor and is therefore often used to dry gases. The ability to absorb water also explains the charring of many organic substances, especially those belonging to the class of carbohydrates (fiber, sugar, etc.), when exposed to concentrated sulfuric acid. Sulfuric acid removes hydrogen and oxygen from carbohydrates, which form water, and carbon is released in the form of coal.

Concentrated sulfuric acid, especially hot, is a vigorous oxidizing agent. It oxidizes HI and HBr (but not HCl) to free halogens, coal to CO 2 , sulfur to SO 2 . These reactions are expressed by the equations:

8HI + H 2 SO 4 \u003d 4I 2 + H 2 S + 4H 2 O;

2HBr + H 2 SO 4 \u003d Br 2 + SO 2 + 2H 2 O;

C + 2H 2 SO 4 \u003d CO 2 + 2SO 2 + 2H 2 O;

S + 2H 2 SO 4 \u003d 3SO 2 + 2H 2 O.

The interaction of sulfuric acid with metals proceeds differently depending on its concentration. Dilute sulfuric acid oxidizes with its hydrogen ion. Therefore, it interacts only with those metals that are in the series of voltages only up to hydrogen, for example:

Zn + H 2 SO 4 \u003d ZnSO 4 + H 2.

However, lead does not dissolve in dilute acid because the resulting PbSO 4 salt is insoluble.

Concentrated sulfuric acid is an oxidizing agent due to sulfur (VI). It oxidizes metals in the voltage series up to and including silver. The products of its reduction can be different depending on the activity of the metal and on the conditions (acid concentration, temperature). When interacting with inactive metals, such as copper, the acid is reduced to SO 2:

Cu + 2H 2 SO 4 \u003d CuSO 4 + SO 2 + 2H 2 O.

When interacting with more active metals, reduction products can be both dioxide and free sulfur and hydrogen sulfide. For example, when interacting with zinc, reactions can occur:

Zn + 2H 2 SO 4 \u003d ZnSO 4 + SO 2 + 2H 2 O;

3Zn + 4H 2 SO 4 = 3ZnSO 4 + S↓ + 4H 2 O;

4Zn + 5H 2 SO 4 \u003d 4ZnSO 4 + H 2 S + 4H 2 O.

The use of sulfuric acid

The use of sulfuric acid varies from country to country and from decade to decade. So, for example, in the USA, the main area of ​​H 2 SO 4 consumption is fertilizer production (70%), followed by chemical production, metallurgy, oil refining (~5% in each area). In the UK, the distribution of consumption by industry is different: only 30% of H 2 SO 4 produced is used in the production of fertilizers, but 18% goes to paints, pigments and dye intermediates, 16% to chemical production, 12% to soap and detergents, 10 % for the production of natural and artificial fibers and 2.5% is used in metallurgy.

Examples of problem solving

EXAMPLE 1

Exercise	Determine the mass of sulfuric acid that can be obtained from one ton of pyrite if the yield of sulfur oxide (IV) in the roasting reaction is 90%, and sulfur oxide (VI) in the catalytic oxidation of sulfur (IV) is 95% of the theoretical.
Decision	Let us write the reaction equation for pyrite firing: 4FeS 2 + 11O 2 \u003d 2Fe 2 O 3 + 8SO 2. Calculate the amount of pyrite substance: n(FeS 2) = m(FeS 2) / M(FeS 2); M (FeS 2) \u003d Ar (Fe) + 2 × Ar (S) \u003d 56 + 2 × 32 \u003d 120 g / mol; n (FeS 2) \u003d 1000 kg / 120 \u003d 8.33 kmol. Since in the reaction equation the coefficient for sulfur dioxide is twice as large as the coefficient for FeS 2, the theoretically possible amount of sulfur oxide (IV) substance is: n (SO 2) theor \u003d 2 × n (FeS 2) \u003d 2 × 8.33 \u003d 16.66 kmol. And practically the amount of mole of sulfur oxide (IV) obtained is: n (SO 2) pract \u003d η × n (SO 2) theor \u003d 0.9 × 16.66 \u003d 15 kmol. Let's write the reaction equation for the oxidation of sulfur oxide (IV) to sulfur oxide (VI): 2SO 2 + O 2 \u003d 2SO 3. The theoretically possible amount of sulfur oxide substance (VI) is: n(SO 3) theor \u003d n (SO 2) pract \u003d 15 kmol. And practically the amount of mole of sulfur oxide (VI) obtained is: n(SO 3) pract \u003d η × n (SO 3) theor \u003d 0.5 × 15 \u003d 14.25 kmol. We write the reaction equation for the production of sulfuric acid: SO 3 + H 2 O \u003d H 2 SO 4. Find the amount of sulfuric acid substance: n (H 2 SO 4) \u003d n (SO 3) pract \u003d 14.25 kmol. The reaction yield is 100%. The mass of sulfuric acid is: m (H 2 SO 4) \u003d n (H 2 SO 4) × M (H 2 SO 4); M(H 2 SO 4) = 2×Ar(H) + Ar(S) + 4×Ar(O) = 2×1 + 32 + 4×16 = 98 g/mol; m (H 2 SO 4) \u003d 14.25 × 98 \u003d 1397 kg.
Answer	The mass of sulfuric acid is 1397 kg

Undiluted sulfuric acid is a covalent compound.

In a molecule, sulfuric acid is tetrahedrally surrounded by four oxygen atoms, two of which are part of the hydroxyl groups. The S–O bonds are double, and the S–OH bonds are single.

Colorless, ice-like crystals have a layered structure: each H 2 SO 4 molecule is connected to four adjacent strong hydrogen bonds, forming a single spatial framework.

The structure of liquid sulfuric acid is similar to the structure of solid one, only the integrity of the spatial frame is broken.

Physical properties of sulfuric acid

Under normal conditions, sulfuric acid is a heavy oily liquid, colorless and odorless. In engineering, sulfuric acid is called its mixtures with both water and sulfuric anhydride. If the molar ratio of SO 3: H 2 O is less than 1, then this is an aqueous solution of sulfuric acid, if more than 1, it is a solution of SO 3 in sulfuric acid.

100% H 2 SO 4 crystallizes at 10.45 °C; T bp = 296.2 °C; density 1.98 g/cm 3 . H 2 SO 4 mixes with H 2 O and SO 3 in any ratio to form hydrates, the heat of hydration is so high that the mixture can boil, splatter and cause burns. Therefore, it is necessary to add acid to water, and not vice versa, since when water is added to acid, lighter water will be on the surface of the acid, where all the heat released will be concentrated.

When aqueous solutions of sulfuric acid containing up to 70% H 2 SO 4 are heated and boiled, only water vapor is released into the vapor phase. Sulfuric acid vapors also appear above more concentrated solutions.

In terms of structural features and anomalies, liquid sulfuric acid is similar to water. Here is the same system of hydrogen bonds, almost the same spatial framework.

Chemical properties of sulfuric acid

Sulfuric acid is one of the strongest mineral acids; due to its high polarity, the H-O bond is easily broken.

Sulfuric acid dissociates in aqueous solution , forming a hydrogen ion and an acid residue:

H 2 SO 4 \u003d H + + HSO 4 -;

HSO 4 - \u003d H + + SO 4 2-.

Summary Equation:

H 2 SO 4 \u003d 2H + + SO 4 2-.

Shows the properties of acids , reacts with metals, metal oxides, bases and salts.

Dilute sulfuric acid does not exhibit oxidizing properties; when it interacts with metals, hydrogen and a salt containing the metal in the lowest oxidation state are released. In the cold, acid is inert to metals such as iron, aluminum, and even barium.

The concentrated acid has oxidizing properties. Possible interaction products simple substances with concentrated sulfuric acid are given in the table. The dependence of the reduction product on the concentration of the acid and the degree of activity of the metal is shown: the more active the metal, the deeper it reduces the sulfate ion of sulfuric acid.

Interaction with oxides:

CaO + H 2 SO 4 \u003d CaSO 4 \u003d H 2 O.

Interaction with bases:

2NaOH + H 2 SO 4 \u003d Na 2 SO 4 + 2H 2 O.

Interaction with salts:

Na 2 CO 3 + H 2 SO 4 = Na 2 SO 4 + CO 2 + H 2 O.

Oxidizing properties

Sulfuric acid oxidizes HI and HBr to free halogens:

H 2 SO 4 + 2HI \u003d I 2 + 2H 2 O + SO 2.

Sulfuric acid takes away chemically bound water from organic compounds containing hydroxyl groups. Dehydration of ethyl alcohol in the presence of concentrated sulfuric acid leads to the production of ethylene:

C 2 H 5 OH \u003d C 2 H 4 + H 2 O.

Charring of sugar, cellulose, starch and other carbohydrates upon contact with sulfuric acid is also explained by their dehydration:

C 6 H 12 O 6 + 12H 2 SO 4 \u003d 18H 2 O + 12SO 2 + 6CO 2.

Sulfur oxide (IV) is highly soluble in water (40 volumes of SO2 dissolve in 1 volume of water at 200C). In this case, sulfurous acid exists only in an aqueous solution:

SO2 + H2O = H2SO3

The reaction of SO2 with water is reversible. In an aqueous solution, sulfur oxide (IV) and sulfurous acid are in chemical equilibrium, which can be displaced. When H2SO3 is bound with alkali (neutralization of the acid), the reaction proceeds towards the formation of sulfurous acid; when removing SO2 (blowing through a nitrogen solution or heating), the reaction proceeds towards the starting materials. Sulfuric acid solution always contains sulfur oxide (IV), which gives it a pungent odor.

sulfurous acid has all the properties of acids. In solution, H2SO3 dissociates in steps:

Н2SO3 H+ + HSO4 –

HSO3 -H++ SO3 2-

As a dibasic acid, it forms two series of salts - sulfites and hydrosulfites. Sulfites are formed when an acid is completely neutralized with an alkali:

H2SO3 + 2NaOH \u003d NaHSO4 + 2H2O

Hydrosulfites are obtained with a lack of alkali (compared to the amount needed to completely neutralize the acid):

H2SO3 + NaOH = NaHSO3 + H2O

Like sulfur oxide (IV), sulfurous acid and its salts are strong reducing agents. At the same time, the degree of oxidation of sulfur increases. So, H2SO3 is easily oxidized into sulfuric acid even by atmospheric oxygen:

2H2SO3+O2= 2H2SO4

Therefore, sulfuric acid solutions that have been stored for a long time always contain sulfuric acid.

The oxidation of sulfurous acid with bromine and potassium permanganate proceeds even more easily:

H2SO3 + Br2 + H2O = H2SO4 + 2HBr

5H2S03+ 2KmnO4= 2H2SO4+ 2MnSO4+ K2SO4+ 2H2O

Sulfur oxide (IV) and sulfurous acid decolorize many dyes, forming colorless compounds with them. The latter can decompose again when heated or in the light, as a result of which the color is restored. Therefore, the bleaching effect of SO2 and H2SO4 is different from that of chlorine. Usually, wool, silk and straw are whitened with sulfur (IV) oxide (these materials are destroyed by chlorine water).

Important application finds a solution of calcium hydrosulfite Ca (HSO3) 2 (sulfite lye), which is used to process wood fibers and paper pulp.

Hydrogen sulfide and sulfides

Hydrogen sulfide H2S is a colorless gas with the smell of rotten eggs. It is highly soluble in water (at 20 °C, 2.5 volumes of hydrogen sulfide dissolve in 1 volume of water). A solution of hydrogen sulfide in water is called hydrogen sulfide water or hydrosulfide acid (it exhibits the properties of a weak acid).

Hydrogen sulfide is very poisonous gas affecting the nervous system. Therefore, it is necessary to work with it in fume hoods or with hermetically sealed devices. The permissible content of H2S in industrial premises is 0.01 mg per 1 liter of air.

Hydrogen sulfide occurs naturally in volcanic gases and in the waters of some mineral springs, for example Pyatigorsk; Matsesta. It is formed during the decay of sulfur-containing organic substances of various plant and animal residues. This explains the characteristic bad smell Wastewater, cesspools and garbage dumps.

Hydrogen sulfide can be obtained by directly combining sulfur with hydrogen when heated:

But usually it is obtained by the action of dilute hydrochloric or sulfuric acid on iron (II) sulfide:

2HCl + FeS = FeCl2 + H2S

This reaction is often carried out in a Kipp apparatus.

H2S is a weaker compound than water. This is due to the large size of the sulfur atom compared to the oxygen atom. Therefore, the H-0 bond is shorter and stronger than the H-S bond. With strong heating, hydrogen sulfide almost completely decomposes into sulfur and hydrogen:

Gaseous H2S burns in air with a blue flame to form sulfur oxide (IV) and water:

2H2S+ 3O2= 2SO2+ 2H2O

With a lack of oxygen, sulfur and water are formed:

2H2S+O2= 2S+ 2H2O

This reaction is used to produce sulfur from hydrogen sulfide on an industrial scale.

Hydrogen sulfide is a fairly strong reducing agent. This important chemical property can be explained as follows. In H2S solution, it is relatively easy to donate electrons to air oxygen molecules:

H2S - 2e- \u003d S + 2H + 2

O2 + 4e- \u003d 2O 2- 1

In this case, H2S is oxidized by atmospheric oxygen to sulfur, which makes hydrogen sulfide water cloudy. Overall reaction equation:

2H2S + O2 = 2S + 2H2O

This also explains the fact that hydrogen sulfide does not accumulate in very large quantities in nature, when organic matter decays, atmospheric oxygen oxidizes it into free sulfur.

Hydrogen sulfide reacts vigorously with halogen solutions. For example:

H2S + I2 = 2HI + S

Sulfur is released and the iodine solution becomes discolored.

Hydrosulfuric acid as a dibasic acid forms two series of salts - medium (sulfides) and acidic (hydrosulfides). For example, Na2S is sodium sulfide, NaHS is sodium hydrosulfide. Almost all hydrosulfides are highly soluble in water. Sulfides of alkali and alkaline earth metals are also soluble in water, while other metals are practically insoluble or slightly soluble; some of them do not dissolve in dilute acids. Therefore, such sulfides can be easily obtained by passing hydrogen sulfide through salts of the corresponding metal, for example:

CuSO4 + H2S = CuS + H2SO4

Some sulfides have a characteristic color: CuS and PbS - black, CdS - yellow, ZnS - white, MnS - pink, SnS - brown, Sb2S3 - orange, etc. The different solubility of sulfides and the different colors of many of them are based qualitative analysis cations.

TICKET #39

Sulfuric acid. Receipt. Physical and chemical properties. The value of sulfuric acid.

Sulfuric acid H2SO4 is a strong dibasic acid, corresponding to the highest oxidation state of sulfur (+6). Under normal conditions, concentrated sulfuric acid is a heavy oily liquid, colorless and odorless, with a sour "coppery" taste. In engineering, sulfuric acid is called its mixtures with both water and sulfuric anhydride SO3. If the molar ratio of SO3: H2O< 1, то это водный раствор серной кислоты, если >1 - solution of SO3 in sulfuric acid (oleum).

When sulfur dioxide (SO 2 ) is dissolved in water, a chemical compound known as sulfurous acid is obtained. The formula of this substance is written as follows: H 2 SO 3. In truth, this compound is extremely unstable, with a certain assumption, it can even be argued that it does not actually exist. Nevertheless, this formula is often used for the convenience of writing chemical reaction equations.

Sulfurous acid: basic properties

For aqueous solution sulfur dioxide is characteristic acidic environment. He himself has all the properties that are inherent in acids, including the neutralization reaction. Sulfurous acid is capable of forming two types of salts: hydrosulfites and ordinary sulfites. Both belong to the group of reducing agents. The first type is usually obtained when sulfurous acid is present in a fairly large amount: H 2 SO 3 + KOH -> KHSO 3 + H 2 O. Otherwise, ordinary sulfite is obtained: H 2 SO 3 + 2KOH -> K 2 SO 3 + 2H 2 O. A qualitative reaction to these salts is their interaction with a strong acid. As a result, SO 2 gas is released, which is easily distinguished by its characteristic pungent odor.

Sulfurous acid can have a bleaching effect. It is no secret that chlorine water also gives a similar effect. However, the compound in question has one important advantage: unlike chlorine, sulfurous acid does not lead to the destruction of dyes, sulfur dioxide forms colorless dyes with them. chemical compounds. This property is often used for bleaching fabrics made of silk, wool, plant material, as well as everything that is destroyed by oxidizing agents containing Cl in its composition. In the old days, this compound was even used to restore the original look of ladies' straw hats. H 2 SO 3 is a fairly strong reducing agent. With the access of oxygen, its solutions gradually turn into sulfuric acid. In those cases when it interacts with a stronger reducing agent (for example, with hydrogen sulfide), sulfuric acid, on the contrary, exhibits oxidizing properties. The dissociation of this substance takes place in two stages. First, the hydrosulfite anion is formed, and then the second step occurs, and it turns into the sulfite anion.

Where is sulfuric acid used?

The production of this substance plays an important role in the production of various wine materials as an antiseptic, in particular, with its help it is possible to prevent the fermentation process of the product in barrels and thereby ensure its safety. It is also used to prevent the fermentation of grain during the extraction of starch from it. Sulfurous acid and preparations based on it have a broad antimicrobial property, and therefore they are often used in the fruit and vegetable industry for canning. Calcium hydrosulfite, also called sulfite liquor, is used to process wood into sulfite pulp, from which paper is subsequently made. It remains to add that for a person this compound is poisonous, and therefore any laboratory works and experiments with it require caution and increased attention.