The structure of the molecule. Sulphuric acid
Acids are chemical compounds consisting of hydrogen atoms and acidic residues, for example, SO4, SO3, PO4, etc. They are inorganic and organic. The former include hydrochloric, phosphoric, sulfide, nitric, sulfuric acid. To the second - acetic, palmitic, formic, stearic, etc.
What is sulfuric acid
This acid consists of two hydrogen atoms and an acid residue SO4. It has the formula H2SO4.
Sulfuric acid, or, as it is also called, sulfate, refers to inorganic oxygen-containing dibasic acids. This substance is considered one of the most aggressive and chemically active. In most chemical reactions, it acts as an oxidizing agent. This acid can be used in concentrated or diluted form, in these two cases it has slightly different chemical properties.
Physical Properties
Sulfuric acid under normal conditions has a liquid state, its boiling point is approximately 279.6 degrees Celsius, the freezing point when it turns into solid crystals is about -10 degrees for one hundred percent and about -20 for 95 percent.
Pure 100% sulphate acid is an odorless and colorless oily liquid substance, which has almost twice the density of water - 1840 kg / m3.
Chemical properties of sulfate acid
Sulfuric acid reacts with metals, their oxides, hydroxides and salts. Diluted with water in various proportions, it can behave differently, so let's take a closer look at the properties of a concentrated and weak solution of sulfuric acid separately.
concentrated sulfuric acid solution
A concentrated solution is considered to be a solution that contains from 90 percent sulfate acid. Such a solution of sulfuric acid is able to react even with inactive metals, as well as with non-metals, hydroxides, oxides, salts. The properties of such a solution of sulfate acid are similar to those of concentrated nitrate acid.
Interaction with metals
During the chemical reaction of a concentrated solution of sulfate acid with metals located to the right of hydrogen in the electrochemical series of metal voltages (that is, with not the most active), the following substances are formed: sulfate of the metal with which the interaction takes place, water and sulfur dioxide. The metals, as a result of interaction with which the listed substances are formed, include copper (cuprum), mercury, bismuth, silver (argentum), platinum and gold (aurum).
Interaction with inactive metals
With metals that are to the left of hydrogen in the voltage series, concentrated sulfuric acid behaves a little differently. As a result of such a chemical reaction, the following substances are formed: sulfate of a certain metal, hydrogen sulfide or pure sulfur and water. The metals with which such a reaction takes place also include iron (ferum), magnesium, manganese, beryllium, lithium, barium, calcium and all the others that are in the series of voltages to the left of hydrogen, except for aluminum, chromium, nickel and titanium - with them concentrated sulfate acid does not react.
Interaction with non-metals
This substance is a strong oxidizing agent, therefore it is able to participate in redox chemical reactions with non-metals, such as, for example, carbon (carbon) and sulfur. As a result of such reactions, water is necessarily released. When this substance is added to carbon, carbon dioxide and sulfur dioxide are also released. And if you add acid to sulfur, you get only sulfur dioxide and water. In such a chemical reaction, sulfate acid plays the role of an oxidizing agent.
Interaction with organic substances
Carbonization can be distinguished among the reactions of sulfuric acid with organic substances. Such a process occurs when a given substance collides with paper, sugar, fibers, wood, etc. In this case, carbon is released in any case. The carbon formed during the reaction can partially interact with sulfuric acid in excess. The photo shows the reaction of sugar with a solution of sulfate acid of medium concentration.
Reactions with salts
Also, a concentrated solution of H2SO4 reacts with dry salts. In this case, a standard exchange reaction occurs, in which metal sulfate is formed, which was present in the structure of the salt, and an acid with a residue that was in the composition of the salt. However, concentrated sulfuric acid does not react with salt solutions.
Interaction with other substances
Also, this substance can react with metal oxides and their hydroxides, in these cases exchange reactions occur, in the first metal sulfate and water are released, in the second - the same.
Chemical properties of a weak solution of sulfate acid
Dilute sulfuric acid reacts with many substances and has the same properties as all acids. It, unlike concentrated, interacts only with active metals, that is, those that are to the left of hydrogen in a series of voltages. In this case, the same substitution reaction occurs, as in the case of any acid. This releases hydrogen. Also, such an acid solution interacts with salt solutions, as a result of which an exchange reaction occurs, already discussed above, with oxides - just like concentrated, with hydroxides - also the same. In addition to ordinary sulfates, there are also hydrosulfates, which are the product of the interaction of hydroxide and sulfuric acid.
How to know if a solution contains sulfuric acid or sulfates
To determine whether these substances are present in a solution, a special qualitative reaction for sulfate ions is used, which allows you to find out. It consists in adding barium or its compounds to the solution. As a result, a white precipitate (barium sulfate) may form, indicating the presence of sulfates or sulfuric acid.
How is sulfuric acid produced?
The most common method of industrial production of this substance is its extraction from iron pyrite. This process occurs in three stages, each of which occurs a certain chemical reaction. Let's consider them. First, oxygen is added to pyrite, resulting in the formation of ferum oxide and sulfur dioxide, which is used for further reactions. This interaction occurs at high temperature. This is followed by a step in which, by adding oxygen in the presence of a catalyst, which is vanadium oxide, sulfur trioxide is obtained. Now, at the last stage, water is added to the resulting substance, and sulfate acid is obtained. This is the most common process for the industrial extraction of sulfate acid, it is used most often because pyrite is the most accessible raw material suitable for the synthesis of the substance described in this article. Sulfuric acid obtained using such a process is used in various industries - both in the chemical industry and in many others, for example, in oil refining, ore dressing, etc. It is also often used in the manufacturing technology of many synthetic fibers .
It has a historical name: vitriol oil. The study of acid began in ancient times, it was described in their writings by the Greek physician Dioscorides, the Roman naturalist Pliny the Elder, the Islamic alchemists Geber, Razi and Ibn Sina, and others. In the Sumerians, there was a list of vitriol, which was classified according to the color of the substance. Nowadays, the word "vitriol" combines crystalline hydrates of divalent metal sulfates.
In the 17th century, the German-Dutch chemist Johann Glauber obtained sulfuric acid by burning sulfur with (KNO3) in the presence of. In 1736, Joshua Ward (a pharmacist from London) used this method in production. This time can be considered a starting point, when sulfuric acid began to be produced on a large scale. Its formula (H2SO4), as is commonly believed, was established by the Swedish chemist Berzelius (1779-1848) a little later.
Berzelius, using alphabetic characters (denoting chemical elements) and subscripts (indicating the number of atoms of a given type in a molecule), found that one molecule contains 1 sulfur atom (S), 2 hydrogen atoms (H) and 4 oxygen atoms (O ). Since that time, the qualitative and quantitative composition of the molecule has become known, that is, sulfuric acid has been described in the language of chemistry.
Showing in graphical form the mutual arrangement of atoms in a molecule and the chemical bonds between them (they are usually denoted by lines), informs that in the center of the molecule there is a sulfur atom, which is connected by double bonds with two oxygen atoms. With the other two oxygen atoms, to each of which a hydrogen atom is attached, the same sulfur atom is connected by single bonds.
Properties
Sulfuric acid is a slightly yellowish or colorless, viscous liquid, soluble in water at any concentration. It is a strong mineral and is highly aggressive towards metals (concentrated does not interact with iron without heating, but passivates it), rocks, animal tissues or other materials. It is characterized by high hygroscopicity and pronounced properties of a strong oxidizing agent. At a temperature of 10.4 °C, the acid solidifies. When heated to 300 °C, almost 99% of the acid loses sulfuric anhydride (SO3).
Its properties change depending on the concentration of its aqueous solution. There are common names for acid solutions. Diluted acid is considered up to 10%. Battery - from 29 to 32%. At a concentration of less than 75% (as established in GOST 2184), it is called a tower. If the concentration is 98%, then it will already be concentrated sulfuric acid. The formula (chemical or structural) remains unchanged in all cases.
When concentrated sulfuric anhydride is dissolved in sulfuric acid, oleum or fuming sulfuric acid is formed, its formula can be written as follows: H2S2O7. Pure acid (H2S2O7) is a solid with a melting point of 36°C. Sulfuric acid hydration reactions are characterized by the release of heat in large quantities.
A dilute acid reacts with metals, reacting with which it exhibits the properties of a strong oxidizing agent. In this case, sulfuric acid is reduced, the formula of the formed substances containing a reduced (up to +4, 0 or -2) sulfur atom can be: SO2, S or H2S.
Reacts with non-metals such as carbon or sulfur:
2 H2SO4 + C → 2 SO2 + CO2 + 2 H2O
2 H2SO4 + S → 3 SO2 + 2 H2O
Reacts with sodium chloride:
H2SO4 + NaCl → NaHSO4 + HCl
It is characterized by the reaction of electrophilic substitution of a hydrogen atom attached to the benzene ring of an aromatic compound by the -SO3H group.
Receipt
In 1831, the contact method for obtaining H2SO4 was patented, which is currently the main one. Today, most sulfuric acid is produced using this method. The raw material used is sulfide ore (more often iron pyrite FeS2), which is fired in special furnaces, and roasting gas is formed. Since the temperature of the gas is 900 ° C, it is cooled with sulfuric acid with a concentration of 70%. Then the gas is cleaned from dust in the cyclone and electrostatic precipitator, in washing towers with acid with a concentration of 40 and 10% of catalytic poisons (As2O5 and fluorine), and on wet electrostatic precipitators from acid aerosol. Next, the roasting gas containing 9% sulfur dioxide (SO2) is dried and fed into the contact apparatus. After passing through 3 layers of vanadium catalyst, SO2 is oxidized to SO3. To dissolve the formed sulfuric anhydride, concentrated sulfuric acid is used. The formula for a solution of sulfuric anhydride (SO3) in anhydrous sulfuric acid is H2S2O7. In this form, oleum in steel tanks is transported to the consumer, where it is diluted to the desired concentration.
Application
Due to its different chemical properties, H2SO4 has a wide range of applications. In the production of acid itself, as an electrolyte in lead-acid batteries, for the manufacture of various cleaning agents, it is also an important reagent in the chemical industry. It is also used in the production of: alcohols, plastics, dyes, rubber, ether, adhesives, soaps and detergents, pharmaceuticals, pulp and paper, petroleum products.
New Topic: Sulfuric Acid -H 2 SO 4
1. Electronic and structural formulas of sulfuric acid
*S - sulfur is in an excited state 1S 2 2S 2 2P 6 3S 1 3P 3 3d 2
The electronic formula of the sulfuric acid molecule:
Structural formula of the sulfuric acid molecule:
1 H - -2 O -2 O
1 H - -2 O -2 O
2. Receipt:
The chemical processes for the production of sulfuric acid can be represented as the following scheme:
S + O 2 + O 2 + H 2 O
FeS 2 SO 2 SO 3 H 2 SO 4
Sulfuric acid is produced in three stages:
1 stage. Sulfur, iron pyrite or hydrogen sulfide are used as raw materials.
4 FeS 2 + 11 O 2 \u003d 2Fe 2 O 3 + 8SO 2
2 stage. Oxidation of SO 2 to SO 3 with oxygen using a catalyst V 2 O 5
2SO 2 + O 2 \u003d 2SO 3 + Q
3rd stage. Not water is used to convert SO 3 to sulfuric acid. there is a strong heating, and a concentrated solution of sulfuric acid.
SO 3 + H 2 O H 2 SO 4
The result is oleum - a solutionSO 3 in sulfuric acid.
Apparatus circuit diagram(see textbook p.105)
3.Physical properties.
a) liquid b) colorless c) heavy (vitriol) d) non-volatile
d) when dissolved in water, strong heating occurs ( so sulfuric acid must be poured intowater,anot vice versa!)
4. Chemical properties of Sulfuric acid.
|
DilutedH 2 SO 4 |
concentratedH 2 SO 4 |
|
Has all the properties of acids |
Has specific properties |
|
1.Changes the color of the indicator: H 2 SO 4 H + + HSO 4 - HSO 4 - H + + SO 4 2- 2.Reacts with metals standing up to hydrogen: Zn + H 2 SO 4 ZnSO 4 +H 2 3. Reacts with basic and amphoteric oxides: MgO + H 2 SO 4 MgSO 4 + H 2 O 4. Interacts with bases (neutralization reaction) 2NaOH + H 2 SO 4 Na 2 SO 4 + 2H 2 O excess acid forms acidic salts NaOH + H 2 SO 4 NaHSO 4 +H 2 O 5. Reacts with dry salts, displacing other acids from them (this is the strongest and non-volatile acid): 2NaCl+H 2 SO 4 Na 2 SO 4 +2HCl 6. Reacts with salt solutions if an insoluble salt is formed: BaCl 2 +H 2 SO 4 BaSO 4 +2HCl- whitesediment qualitative reaction to an ionSO 4 2- 7. When heated, it decomposes: H 2 SO 4 H 2 O + SO 3 |
1. Concentrated H 2 SO 4 is the strongest oxidizing agent; when heated, it reacts with all metals (except Au and Pt). In these reactions, depending on the activity of the metal and the conditions, S, SO 2 or H 2 S are released For example: Cu+ conc 2H 2 SO 4 CuSO 4 +SO 2 +H 2 O 2.conc. H 2 SO 4 passivates iron and aluminum, therefore it can be transported in steel and aluminum tanks. 3. conc. H 2 SO 4 absorbs water well H 2 SO 4 + H 2 O H 2 SO 4 * 2H 2 O Therefore, it chars organic matter |
5.Application: Sulfuric acid is one of the most important products used in various industries. Its main consumers are the production of mineral fertilizers, metallurgy, and refining of petroleum products. Sulfuric acid is used in the manufacture of other acids, detergents, explosives, medicines, paints, and as electrolytes for lead-acid batteries. (Textbook p.103).
6.Salts of sulfuric acid
Sulfuric acid dissociates in steps
H 2 SO 4 H + + HSO 4 -
HSO 4 - H + + SO 4 2-
therefore, it forms two types of salts - sulfates and hydrosulfates
For example: Na 2 SO 4 - sodium sulfate (medium salt)
Na HSO 4 - sodium hydrogen sulfate (acid salt)
The most widely used are:
Na 2 SO 4 * 10H 2 O - Glauber's salt (used in the production of soda, glass, in medicine and
veterinary medicine.
CaSO 4 * 2H 2 O - gypsum
CuSO 4 * 5H 2 O - copper sulfate (used in agriculture).
Laboratory experience
Chemical properties of sulfuric acid.
Equipment: Test tubes.
Reagents: sulfuric acid, methyl orange, zinc, magnesium oxide, sodium hydroxide and phenolphthalein, sodium carbonate, barium chloride.
b) Fill in the table of observations
Structural formula
True, empirical, or gross formula: H2SO4
Chemical composition of sulfuric acid
Molecular weight: 98.076
Sulphuric acid H 2 SO 4 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 technology, sulfuric acid is called its mixtures with both water and sulfuric anhydride SO 3. 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 - a solution of SO 3 in sulfuric acid (oleum).
Name
In the XVIII-XIX centuries, sulfur for gunpowder was produced from sulfur pyrites (pyrite) at vitriol plants. Sulfuric acid at that time was called "vitriol oil" (as a rule it was a crystalline hydrate, resembling oil in consistency), the origin of the name of its salts (or rather, crystalline hydrates) - vitriol, is obviously from here.
Getting sulfuric acid
Industrial (contact) method
In industry, sulfuric acid is produced by the oxidation of sulfur dioxide (sulphurous gas produced during the combustion of sulfur or sulfur pyrite) to trioxide (sulfuric anhydride), followed by the interaction of SO 3 with water. The sulfuric acid obtained by this method is also called contact (concentration 92-94%).
Nitrous (tower) method
Previously, sulfuric acid was obtained exclusively by the nitrous method in special towers, and the acid was called tower acid (75% concentration). The essence of this method is the oxidation of sulfur dioxide with nitrogen dioxide in the presence of water.
Another way
In those rare cases when hydrogen sulfide (H 2 S) displaces sulfate (SO 4 -) from salt (with metals Cu, Ag, Pb, Hg), sulfuric acid is a by-product. Sulfides of these metals have the highest strength, as well as a distinctive black color.
Physical and physico-chemical properties
A very strong acid, at 18 o C pK a (1) \u003d -2.8, pK a (2) \u003d 1.92 (K z 1.2 10 -2); bond lengths in the molecule S=O 0.143 nm, S-OH 0.154 nm, angle HOSOH 104°, OSO 119°; boils, forming an azeotropic mixture (98.3% H 2 SO 4 and 1.7% H 2 O with a boiling point of 338.8 ° C). Sulfuric acid, corresponding to 100% H 2 SO 4 content, has a composition (%): H 2 SO 4 99.5, HSO 4 - - 0.18, H 3 SO 4 + - 0.14, H 3 O + - 0.09, H 2 S 2 O 7 , - 0.04, HS 2 O 7 - - 0.05. Miscible with water and SO 3 in all proportions. In aqueous solutions, sulfuric acid almost completely dissociates into H 3 O + , HSO 3 + , and 2HSO 4 - . Forms hydrates H 2 SO 4 nH 2 O, where n = 1, 2, 3, 4 and 6.5.
Oleum
Solutions of sulfuric anhydride SO 3 in sulfuric acid are called oleum, they form two compounds H 2 SO 4 SO 3 and H 2 SO 4 2SO 3. Oleum also contains pyrosulfuric acids. The boiling point of aqueous solutions of sulfuric acid increases with an increase in its concentration and reaches a maximum at a content of 98.3% H 2 SO 4 . The boiling point of oleum decreases with increasing SO 3 content. With an increase in the concentration of aqueous solutions of sulfuric acid, the total vapor pressure over the solutions decreases and at a content of 98.3% H 2 SO 4 reaches a minimum. With an increase in the concentration of SO 3 in oleum, the total vapor pressure above it increases. The vapor pressure over aqueous solutions of sulfuric acid and oleum can be calculated by the equation:
log p=A-B/T+2.126
the values of the coefficients A and B depend on the concentration of sulfuric acid. Steam over aqueous solutions of sulfuric acid consists of a mixture of water vapor, H 2 SO 4 and SO 3, while the composition of the vapor differs from the composition of the liquid at all concentrations of sulfuric acid, except for the corresponding azeotropic mixture. As the temperature rises, dissociation increases. The oleum H 2 SO 4 ·SO 3 has the maximum viscosity; with increasing temperature, η decreases. The electrical resistance of sulfuric acid is minimal at a concentration of SO 3 and 92% H 2 SO 4 and maximum at a concentration of 84 and 99.8% H 2 SO 4 . For oleum, the minimum ρ is at a concentration of 10% SO 3 . As the temperature rises, the ρ of sulfuric acid increases. Dielectric constant of 100% sulfuric acid 101 (298.15 K), 122 (281.15 K); cryoscopic constant 6.12, ebulioscopic constant 5.33; the diffusion coefficient of sulfuric acid vapor in air varies with temperature; D = 1.67 10⁻⁵T3/2 cm²/s.
Chemical properties
Sulfuric acid in concentrated form when heated is a fairly strong oxidizing agent. Oxidizes HI and partially HBr to free halogens. Oxidizes many metals (exceptions: Au, Pt, Ir, Rh, Ta.). In this case, concentrated sulfuric acid is reduced to SO 2 . In the cold in concentrated sulfuric acid, Fe, Al, Cr, Co, Ni, Ba are passivated and the reactions do not proceed. With the strongest reducing agents, concentrated sulfuric acid is reduced to S and H 2 S. Concentrated sulfuric acid absorbs water vapor, so it is used for drying gases, liquids and solids, for example, in desiccators. However, concentrated H 2 SO 4 is partially reduced by hydrogen, which is why it cannot be used for drying it. Splitting water from organic compounds and leaving black carbon (coal) at the same time, concentrated sulfuric acid leads to the carbonization of wood, sugar and other substances. Diluted H 2 SO 4 interacts with all metals that are in the electrochemical series of voltages to the left of hydrogen with its release. Oxidizing properties for dilute H 2 SO 4 are uncharacteristic. Sulfuric acid forms two series of salts: medium - sulfates and acidic - hydrosulfates, as well as esters. Peroxomonosulfuric (or Caro's acid) H 2 SO 5 and peroxodisulfuric H 2 S 2 O 8 acids are known. Sulfuric acid also reacts with basic oxides to form sulfate and water. In metalworking plants, a sulfuric acid solution is used to remove a layer of metal oxide from the surface of metal products that are subjected to strong heating during the manufacturing process. So, iron oxide is removed from the surface of sheet iron by the action of a heated solution of sulfuric acid. A qualitative reaction to sulfuric acid and its soluble salts is their interaction with soluble barium salts, which forms a white precipitate of barium sulfate, insoluble in water and acids, for example.
Application
Sulfuric acid is used:
- in the processing of ores, especially in the extraction of rare elements, including uranium, iridium, zirconium, osmium, etc.;
- in the production of mineral fertilizers;
- as an electrolyte in lead batteries;
- to obtain various mineral acids and salts;
- in the production of chemical fibers, dyes, smoke-forming and explosive substances;
- in the oil, metalworking, textile, leather and other industries;
- in the food industry - registered as a food additive E513 (emulsifier);
- in industrial organic synthesis in reactions:
- dehydration (obtaining diethyl ether, esters);
- hydration (ethanol from ethylene);
- sulfonation (synthetic detergents and intermediates in the production of dyes);
- alkylation (obtaining isooctane, polyethylene glycol, caprolactam), etc.
- For the recovery of resins in filters in the production of distilled water.
World production of sulfuric acid approx. 160 million tons per year. The largest consumer of sulfuric acid is the production of mineral fertilizers. For P 2 O 5 phosphate fertilizers, 2.2-3.4 times more sulfuric acid is consumed by mass, and for (NH 4) 2 SO 4 sulfuric acid 75% of the mass of consumed (NH 4) 2 SO 4. Therefore, sulfuric acid plants tend to be built in conjunction with plants for the production of mineral fertilizers.
Historical information
Sulfuric acid has been known since antiquity, occurring in nature in a free form, for example, in the form of lakes near volcanoes. Perhaps the first mention of acid gases obtained by calcining alum or iron sulfate "green stone" is found in writings attributed to the Arab alchemist Jabir ibn Hayyan. In the 9th century, the Persian alchemist Ar-Razi, calcining a mixture of iron and copper sulfate (FeSO 4 7H 2 O and CuSO 4 5H 2 O), also obtained a solution of sulfuric acid. This method was perfected by the European alchemist Albert Magnus, who lived in the 13th century. Scheme for the production of sulfuric acid from ferrous sulfate - thermal decomposition of iron (II) sulfate, followed by cooling the mixture. The works of the alchemist Valentine (XIII century) describe a method for producing sulfuric acid by absorbing gas (sulphuric anhydride) released by burning a mixture of sulfur and saltpeter powders with water. Subsequently, this method formed the basis of the so-called. "chamber" method, carried out in small chambers lined with lead, which does not dissolve in sulfuric acid. In the USSR, such a method existed until 1955. Alchemists of the 15th century also knew a method for obtaining sulfuric acid from pyrite - sulfur pyrite, a cheaper and more common raw material than sulfur. Sulfuric acid was produced in this way for 300 years, in small quantities in glass retorts. Subsequently, due to the development of catalysis, this method replaced the chamber method for the synthesis of sulfuric acid. Currently, sulfuric acid is produced by catalytic oxidation (on V 2 O 5) of sulfur oxide (IV) to sulfur oxide (VI), and subsequent dissolution of sulfur oxide (VI) in 70% sulfuric acid to form oleum. In Russia, the production of sulfuric acid was first organized in 1805 near Moscow in the Zvenigorod district. In 1913, Russia ranked 13th in the world in the production of sulfuric acid.
additional information
The smallest droplets of sulfuric acid can form in the middle and upper atmosphere as a result of the reaction of water vapor and volcanic ash containing large amounts of sulfur. The resulting suspension, due to the high albedo of sulfuric acid clouds, makes it difficult for sunlight to reach the surface of the planet. Therefore (and also as a result of a large number of tiny particles of volcanic ash in the upper atmosphere, which also make it difficult for sunlight to reach the planet), significant climate changes can occur after especially strong volcanic eruptions. For example, as a result of the eruption of the Ksudach volcano (Kamchatka Peninsula, 1907), an increased concentration of dust in the atmosphere persisted for about 2 years, and characteristic silvery clouds of sulfuric acid were observed even in Paris. The explosion of the Pinatubo volcano in 1991, which sent 3 10 7 tons of sulfur into the atmosphere, led to the fact that 1992 and 1993 were much colder than 1991 and 1994.
Standards
- Sulfuric acid technical GOST 2184-77
- Sulfuric acid battery. Specifications GOST 667-73
- Sulfuric acid of special purity. Specifications GOST 1422-78
- Reagents. Sulfuric acid. Specifications GOST 4204-77
Target: To get acquainted with the structure, physical and chemical properties, the use of sulfuric acid.
Educational tasks: Consider the physical and chemical properties (common with other acids and specific) of sulfuric acid, obtaining, show the great importance of sulfuric acid and its salts in the national economy.
Educational tasks: To continue the formation of a dialectical-materialistic understanding of nature among students.
Development tasks: Development of general educational skills and abilities, work with a textbook and additional literature, rules for working on a desktop, the ability to systematize and generalize, establish cause-and-effect relationships, express one’s thoughts conclusively and competently, draw conclusions, draw diagrams, sketch.
During the classes
1. Repetition of the past.
Frontal class survey. Compare the properties of crystalline and plastic sulfur. Explain the essence of allotropy.
2. Learning new material.
After carefully listening to the tale, we will explain at the end of the lesson why sulfuric acid behaved strangely with water, wood and a golden ring.
Sounds like an audio recording.
The Adventures of Sulfuric Acid.
In one chemical kingdom lived a sorceress, her name was sulfuric acid. It didn't look so bad, it was a colorless liquid, viscous like oil, odorless. Sulphuric acid I wanted to be famous, so I went on a trip.
She had already been walking for 5 hours, and since the day was too hot, she was very thirsty. And suddenly she saw a well. "Water!" acid exclaimed, and running to the well, she touched the water. The water hissed terribly. With a cry, the frightened sorceress rushed away. Of course, the young acid did not know that when mixed sulfuric acid water releases a large amount of heat.
"If water comes into contact with sulfuric acid, then the water, not having time to mix with the acid, can boil and throw out splashes sulfuric acid. This entry appeared in the diary of a young traveler, and then entered the textbooks.
Since the acid did not quench their thirst, then, a sprawling tree, decided to lie down and rest in the shade. But she didn't succeed either. Once Sulphuric acid touched the tree, it began to char. Not knowing the reason for this, the frightened acid ran away.
Soon she came to the city and decided to go to the first store that came across her way. They turned out to be jewelry. Approaching the shop windows, the acid saw many beautiful rings. Sulphuric acid I decided to try one ring. Asking the seller for a gold ring, the traveler put it on her long beautiful finger. The sorceress really liked the ring and she decided to buy it. That's what she could boast to her friends!
Leaving the city, the acid went home. On the way, the thought did not leave her, why did water and wood behave so strangely when touched with her, but nothing happened to this golden thing? “Yes, because gold is in sulfuric acid does not oxidize. These were the last words written by acid in his diary.
Teacher's explanation.
Electronic and structural formulas of sulfuric acid.
Since sulfur is in the 3rd period of the periodic system, the octet rule (eight electronic structure) is not respected and a sulfur atom can acquire up to twelve electrons. The electronic and structural formulas of sulfuric acid are as follows:
(The six electrons of sulfur are marked with an asterisk)
Receipt.
Sulfuric acid is formed by the interaction of sulfur oxide (5) with water (SO 3 + H 2 O -> H 2 SO 4).
physical properties.
Sulfuric acid is a colorless, heavy, non-volatile liquid. When dissolved in water, a very strong heating occurs. remember, that do not pour water into concentrated sulfuric acid!
Concentrated sulfuric acid absorbs water vapor from the air. This can be seen if an open vessel with concentrated sulfuric acid is balanced on a scale: after a while, the cup with the vessel will sink.
Chemical properties.
Dilute sulfuric acid has properties common to all acids. In addition, sulfuric acid has specific properties.
Chemical properties of sulfuric - Application .
Demonstration by the teacher of an entertaining experience.
Brief safety briefing.
Eskimo (Charcoal from sugar)
| Equipment | Experience Plan | Conclusion |
|
Pour 30 g of powdered sugar into a beaker. Use a beaker to measure out 12 ml of concentrated sulfuric acid. Mix sugar and acid in a glass with a glass rod into a mushy mass (remove the glass rod and put it in a glass of water). After some time, the mixture darkens, warms up, and soon a porous coal mass begins to crawl out of the glass - popsicle | Carbonization of sugar with sulfuric acid (concentrated) is explained by the oxidizing properties of this acid. The reducing agent is carbon. The process is exothermic. 2H 2 SO 4 + C 12 O 11 + H22 -> 11C + 2SO 2 + 13H 2 O + CO 2 |
Students fill out a table with an entertaining experience in a notebook.
Students' reasoning about why Sulfuric acid behaved so strangely with water, wood and gold.
Application.
Due to its properties (the ability to absorb water, oxidizing properties, non-volatility), sulfuric acid is widely used in the national economy. It belongs to the main products of the chemical industry.
- receiving dyes;
- obtaining mineral fertilizers;
- cleaning of oil products;
- electrolytic production of copper;
- electrolyte in batteries;
- receiving explosives;
- receiving dyes;
- obtaining artificial silk;
- receiving glucose;
- obtaining salts;
- obtaining acids.
Salts of sulfuric acid are widely used, for example
Na 2 SO 4 * 10H 2 O– sodium sulfate crystalline hydrate (Glauber's salt)- used in the production of soda, glass, in medicine and veterinary medicine.
CaSO4*2H2O- hydrated calcium sulfate (natural gypsum)- used to obtain semi-aqueous gypsum, which is necessary in construction, and in medicine - for applying plaster bandages.
CuSO4*5H2O– hydrated copper sulfate (2) (copper sulfate)- used in the fight against pests and plant diseases.
The work of students with the extra-textual component of the textbook.
It is interesting
…in the Gulf of Kara-Bogaz-Gol, the water contains 30% of Glauber's salt at a temperature of +5 ° C, this salt precipitates as a white precipitate, like snow, and with the onset of warm weather, the salt dissolves again. Since Glauber's salt appears and disappears in this bay, it was named mirabilite, which means "wonderful salt".
3. Questions to consolidate the educational material, written on the board.
- In winter, a vessel with concentrated sulfuric acid is sometimes placed between the window frames. What is the purpose of doing this, why can't the vessel be filled with acid to the top?
- Why is sulfuric acid called the "bread" of chemistry?
Homework and instructions for its implementation.
Where appropriate, write equations in ionic form.
Conclusion on the lesson, setting and commenting marks.
References.
- Rudzitis G.E. Feldman F.G., Chemistry: A textbook for grades 7-11 of an evening (shift) secondary school at 2 hours. Part 1-3 edition - M .: Education, 1987.
- Chemistry at school No. 6, 1991.
- Strempler Genrikh Ivanovich, Chemistry at leisure: Book. for students Wednesdays. and old. age /Fig. ed. with the participation of V.N. Rastopchiny.- F .: Ch. ed. KSE, 1990.
