Chemical formula h2so4. Sulfuric acid structural chemical formula

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 great 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 products of interaction of 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 removes 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.

Physical properties of sulfuric acid:
Heavy oily liquid ("vitriol");
density 1.84 g/cm3; non-volatile, highly soluble in water - with strong heating; t°pl. = 10.3°C, bp \u003d 296 ° C, very hygroscopic, has water-removing properties (charring of paper, wood, sugar).

The heat of hydration is so great that the mixture may 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.

Industrial production of sulfuric acid (contact method):

1) 4FeS 2 + 11O 2 → 2Fe 2 O 3 + 8SO 2

2) 2SO 2 + O 2 V 2 O 5 → 2SO 3

3) nSO 3 + H 2 SO 4 → H 2 SO 4 nSO 3 (oleum)

Crushed purified wet pyrite (sulfur pyrite) is poured from above into the kiln for firing in " fluidized bed". From below (counterflow principle) air enriched with oxygen is passed through.
Furnace gas comes out of the furnace, the composition of which is: SO 2, O 2, water vapor (pyrite was wet) and the smallest particles of cinder (iron oxide). The gas is purified from impurities of solid particles (in a cyclone and electrostatic precipitator) and water vapor (in a drying tower).
In the contact apparatus, sulfur dioxide is oxidized using a V 2 O 5 catalyst (vanadium pentoxide) to increase the reaction rate. The process of oxidation of one oxide to another is reversible. Therefore, the optimal conditions for the course of the direct reaction are selected - increased pressure (because the direct reaction occurs with a decrease in the total volume) and a temperature not higher than 500 C (because the reaction is exothermic).

In the absorption tower, sulfur oxide (VI) is absorbed by concentrated sulfuric acid.
Water absorption is not used, because sulfur oxide dissolves in water with the release of a large amount of heat, so the resulting sulfuric acid boils and turns into steam. In order to avoid the formation of sulfuric acid mist, use 98% concentrated sulfuric acid. Sulfur oxide dissolves very well in such an acid, forming oleum: H 2 SO 4 nSO 3

Chemical properties of sulfuric acid:

H 2 SO 4 is a strong dibasic acid, one of the strongest mineral acids, because of the high polarity, the H - O bond is easily broken.

1) 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-.

2) The interaction of sulfuric acid with metals:
Dilute sulfuric acid only dissolves metals in the voltage series to the left of hydrogen:
Zn 0 + H 2 +1 SO 4 (razb) → Zn +2 SO 4 + H 2

3) Sulfuric acid interactionwith basic oxides:
CuO + H 2 SO 4 → CuSO 4 + H 2 O

4) The interaction of sulfuric acid withhydroxides:
H 2 SO 4 + 2NaOH → Na 2 SO 4 + 2H 2 O
H 2 SO 4 + Cu(OH) 2 → CuSO 4 + 2H 2 O

5) Exchange reactions with salts:
BaCl 2 + H 2 SO 4 → BaSO 4 ↓ + 2HCl
The formation of a white precipitate of BaSO 4 (insoluble in acids) is used to detect sulfuric acid and soluble sulfates (qualitative reaction for sulfate ion).

Special properties of concentrated H 2 SO 4:

1) concentrated sulfuric acid is strong oxidizing agent ; when interacting with metals (except Au, Pt) recover to S +4 O 2 , S 0 or H 2 S -2 depending on the activity of the metal. Without heating, it does not react with Fe, Al, Cr - passivation. When interacting with metals with variable valence, the latter are oxidized to higher oxidation states than in the case of a dilute acid solution: Fe0→ Fe 3+ , Cr 0→ Cr 3+ , Mn 0→Mn4+,sn 0→ sn 4+

active metal

8 Al + 15 H 2 SO 4 (conc.) → 4Al 2 (SO 4) 3 + 12H 2 O + 3 H 2 S
4│2Al 0 – 6 e- → 2Al 3+ - oxidation
3│ S 6+ + 8e → S 2– recovery

4Mg+ 5H 2 SO 4 → 4MgSO 4 + H 2 S + 4H 2 O

Medium activity metal

2Cr + 4 H 2 SO 4 (conc.) → Cr 2 (SO 4) 3 + 4 H 2 O + S
1│ 2Cr 0 - 6e → 2Cr 3+ - oxidation
1│ S 6+ + 6e → S 0 - recovery

Metal inactive

2Bi + 6H 2 SO 4 (conc.) → Bi 2 (SO 4) 3 + 6H 2 O + 3 SO2
1│ 2Bi 0 - 6e → 2Bi 3+ - oxidation
3│ S 6+ + 2e →S 4+ - recovery

2Ag + 2H 2 SO 4 → Ag 2 SO 4 + SO 2 + 2H 2 O

2) Concentrated sulfuric acid oxidizes some non-metals, as a rule, to the maximum oxidation state, it itself is reduced toS+4O2:

C + 2H 2 SO 4 (conc) → CO 2 + 2SO 2 + 2H 2 O

S+ 2H 2 SO 4 (conc) → 3SO 2 + 2H 2 O

2P+ 5H 2 SO 4 (conc) → 5SO 2 + 2H 3 PO 4 + 2H 2 O

3) Oxidation of complex substances:
Sulfuric acid oxidizes HI and HBr to free halogens:
2 KBr + 2H 2 SO 4 \u003d K 2 SO 4 + SO 2 + Br 2 + 2H 2 O
2 KI + 2H 2 SO 4 \u003d K 2 SO 4 + SO 2 + I 2 + 2H 2 O
Concentrated sulfuric acid cannot oxidize chloride ions to free chlorine, which makes it possible to obtain HCl by the exchange reaction:
NaCl + H 2 SO 4 (conc.) = NaHSO 4 + HCl

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.

Any acid is a complex substance, the molecule of which contains one or more hydrogen atoms and an acid residue.

The formula of sulfuric acid is H2SO4. Therefore, the composition of the sulfuric acid molecule includes two hydrogen atoms and the acid residue SO4.

Sulfuric acid is formed when sulfur oxide reacts with water

SO3+H2O -> H2SO4

Pure 100% sulfuric acid (monohydrate) is a heavy liquid, viscous like oil, colorless and odorless, with a sour "copper" taste. Already at a temperature of +10 ° C, it solidifies and turns into a crystalline mass.

Concentrated sulfuric acid contains approximately 95% H2SO4. And it freezes at temperatures below -20 ° C.

Interaction with water

Sulfuric acid is highly soluble in water, mixing with it in any ratio. This releases a large amount of heat.

Sulfuric acid is able to absorb water vapor from the air. This property is used in industry for drying gases. Gases are dried by passing them through special containers with sulfuric acid. Of course, this method can only be used for those gases that do not react with it.

It is known that when sulfuric acid comes into contact with many organic substances, especially carbohydrates, these substances are charred. The fact is that carbohydrates, like water, contain both hydrogen and oxygen. Sulfuric acid robs them of these elements. What remains is coal.

In an aqueous solution of H2SO4, the indicators litmus and methyl orange turn red, which indicates that this solution has a sour taste.

Interaction with metals

Like any other acid, sulfuric acid is capable of replacing hydrogen atoms with metal atoms in its molecule. It interacts with almost all metals.

dilute sulfuric acid reacts with metals like a normal acid. As a result of the reaction, a salt with an acidic residue SO4 and hydrogen are formed.

Zn + H2SO4 = ZnSO4 + H2

BUT concentrated sulfuric acid is a very strong oxidizing agent. It oxidizes all metals, regardless of their position in the voltage series. And when reacting with metals, it itself is reduced to SO2. Hydrogen is not released.

Сu + 2 H2SO4 (conc) = CuSO4 + SO2 + 2H2O

Zn + 2 H2SO4 (conc) = ZnSO4 + SO2 + 2H2O

But gold, iron, aluminum, platinum group metals do not oxidize in sulfuric acid. Therefore, sulfuric acid is transported in steel tanks.

Sulfuric acid salts, which are obtained as a result of such reactions, are called sulfates. They are colorless and crystallize easily. Some of them are highly soluble in water. Only CaSO4 and PbSO4 are sparingly soluble. BaSO4 is almost insoluble in water.

Interaction with bases

The reaction of an acid with a base is called a neutralization reaction. As a result of the neutralization reaction of sulfuric acid, a salt containing the acid residue SO4 and water H2O is formed.

Examples of sulfuric acid neutralization reactions:

H2SO4 + 2 NaOH = Na2SO4 + 2 H2O

H2SO4 + CaOH = CaSO4 + 2 H2O

Sulfuric acid enters into a neutralization reaction with both soluble and insoluble bases.

Since there are two hydrogen atoms in the sulfuric acid molecule, and two bases are required to neutralize it, it belongs to dibasic acids.

Interaction with basic oxides

From the school chemistry course, we know that oxides are called complex substances, which include two chemical elements, one of which is oxygen in the oxidation state -2. Basic oxides are called oxides of 1, 2 and some 3 valence metals. Examples of basic oxides: Li2O, Na2O, CuO, Ag2O, MgO, CaO, FeO, NiO.

With basic oxides, sulfuric acid enters into a neutralization reaction. As a result of such a reaction, as in the reaction with bases, salt and water are formed. The salt contains the acid residue SO4.

CuO + H2SO4 = CuSO4 + H2O

Salt interaction

Sulfuric acid reacts with salts of weaker or volatile acids, displacing these acids from them. As a result of this reaction, a salt with an acidic residue SO4 and an acid

H2SO4+BaCl2=BaSO4+2HCl

The use of sulfuric acid and its compounds

Barium porridge BaSO4 is able to delay x-rays. Filling it with the hollow organs of the human body, radiologists examine them.

In medicine and construction, natural gypsum CaSO4 * 2H2O, calcium sulfate hydrate is widely used. Glauber's salt Na2SO4 * 10H2O is used in medicine and veterinary medicine, in the chemical industry - for the production of soda and glass. Copper sulfate CuSO4 * 5H2O is known to gardeners and agronomists who use it to control pests and plant diseases.

Sulfuric acid is widely used in various industries: chemical, metalworking, petroleum, textile, leather and others.

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 (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 letter symbols (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.

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. Sulfuric 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 Sulfuric 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. Sulfuric 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 - Appendix .

Demonstration by the teacher of an entertaining experience.

Brief safety briefing.

Eskimo (Charcoal from sugar)

Equipment	Experience plan	Conclusion
Powdered sugar. concentrated sulfuric acid. Two chemical glasses of 100-150 ml. Glass rod. Scales.	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;
receiving 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 Kara-Bogaz-Gol Bay, the water contains 30% Glauber's salt at a temperature of +5 ° C, this salt precipitates in the form of 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.