FeS + 2HCl = FeCl 2 + H 2 S

Reaction of aluminum sulfide with cold water

Al 2 S 3 + 6H 2 O = 2Al(OH) 3 + 3H 2 S

Direct synthesis from elements occurs when hydrogen is passed over molten sulfur:

H 2 + S = H 2 S.

Heating a mixture of paraffin and sulfur.

1.9. Hydrogen sulfide acid and its salts

Hydrogen sulfide acid has all the properties of weak acids. It reacts with metals, metal oxides, bases.

As a dibasic acid, it forms two types of salts - sulfides and hydrosulfides . Hydrosulfides are highly soluble in water, sulfides of alkali and alkaline earth metals as well, and sulfides of heavy metals are practically insoluble.

Sulfides of alkali and alkaline earth metals are not colored, the rest have a characteristic color, for example, sulfides of copper (II), nickel and lead - black, cadmium, indium, tin - yellow, antimony - orange.

Ionic alkali metal sulfides M 2 S have a fluorite-type structure, where each sulfur atom is surrounded by a cube of 8 metal atoms and each metal atom is surrounded by a tetrahedron of 4 sulfur atoms. MS-type sulfides are characteristic of alkaline earth metals and have a sodium chloride-type structure, where each metal and sulfur atom is surrounded by an octahedron of atoms of a different type. As the covalent nature of the metal–sulfur bond increases, structures with lower coordination numbers are realized.

Sulfides of non-ferrous metals are found in nature as minerals and ores and serve as raw materials for the production of metals.

Preparation of sulfides

Direct interaction of simple substances when heated in an inert atmosphere

Reduction of solid salts of oxoacids

BaSO 4 + 4C = BaS + 4CO (at 1000°C)

SrSO 3 + 2NH 3 = SrS + N 2 + 3H 2 O (at 800°C)

CaCO 3 + H 2 S + H 2 = CaS + CO + 2H 2 O (at 900°C)

Slightly soluble metal sulfides are precipitated from their solutions by the action of hydrogen sulfide or ammonium sulfide

Mn(NO 3) 2 + H 2 S = MnS↓ + 2HNO 3

Pb(NO 3) 2 + (NH 4) 2 S = PbS↓ + 2NH 4 NO 3

Chemical properties of sulfides

Soluble sulfides in water are highly hydrolyzed and have an alkaline environment:

Na 2 S + H 2 O = NaHS + NaOH;

S 2- + H 2 O = HS - + OH - .

Oxidized by air oxygen, depending on conditions, the formation of oxides, sulfates and metals is possible:

2CuS + 3O 2 = 2CuO + 2SO 2;

CaS + 2O 2 = CaSO 4;

Ag 2 S + O 2 = 2Ag + SO 2.

Sulfides, especially those soluble in water, are strong reducing agents:

2KMnO 4 + 3K 2 S + 4H 2 O = 3S + 2MnO 2 + 8KOH.

1.10. Hydrogen sulfide toxicity

In air, hydrogen sulfide ignites at about 300 °C. Its mixtures with air containing from 4 to 45% H 2 S are explosive. The toxicity of hydrogen sulfide is often underestimated and work with it is carried out without taking sufficient precautions. Meanwhile, even 0.1% H 2 S in the air quickly causes severe poisoning. When hydrogen sulfide is inhaled in significant concentrations, fainting or even death from respiratory paralysis can occur instantly (if the victim was not promptly removed from the poisoned atmosphere). The first symptom of acute poisoning is loss of smell. In the future there will be headache, dizziness and nausea. Sometimes, after a while, sudden fainting occurs. The antidote is, first of all, clean air. Those severely poisoned by hydrogen sulfide are given oxygen to breathe. Sometimes artificial respiration has to be used. Chronic poisoning with small amounts of H 2 S causes a general deterioration in health, emaciation, headaches, etc. The maximum permissible concentration of H 2 S in the air of industrial premises is considered to be 0.01 mg/l.

Lesson objectives: to consider the properties of sulfur compounds - hydrogen sulfide, hydrogen sulfide acid and its salts; sulfurous acid and its salts.

Equipment: samples of sulfides, metal sulfites, computer presentation.

During the classes

I. Preparation for the lesson

(Check the readiness of groups of students, equipment, class for the lesson; mark absent students in the class register; report the topic and goals of the lesson).

II. Testing students' knowledge.

1. Solve the problem “Slide No. 1-1”:

Native sulfur containing 30% impurities was used to obtain sulfur (IV) oxide weighing 8 g. Determine the mass (in grams) of native sulfur.

Answer: m(S) = 5.7 g.

2. Oral questions:

• Tell us about the structure of the sulfur atom and its oxidation state.
• Describe the allotropy of sulfur.
• Explain the chemical properties of sulfur.

3. Write the equation chemical reaction from the point of view of electrolytic dissociation between zinc sulfate and potassium hydroxide “Slide No. 1-1”.

4. Writing check homework– 6 students.

5. Block of questions “Slide No. 2”:

• Read the formulation of the Periodic Law given by D.I. Mendeleev (the properties of chemical elements and substances formed by them periodically depend on relative atomic masses elements).
• Read the modern formulation of the Periodic Law (the properties of chemical elements and the substances formed by them are periodically dependent on the charges of their atomic nuclei).
• What is a chemical element called? (a chemical element is atoms of the same type)
• In what forms does it exist? chemical element? (a chemical element exists in three forms: free atoms, simple substances, complex substances).
• What substances are called simple? (simple substances are substances whose molecules are formed by atoms of one chemical element).
• What substances are called complex? (complex substances are substances whose molecules are formed by atoms of different chemical elements).
• What classes are complex substances divided into? (complex substances are divided into four classes: oxides, bases, acids, salts).
• What substances are called salts? (salts are complex substances whose molecules consist of metal atoms and acid residues).
• What substances are called acids? (acids are complex substances whose molecule consists of hydrogen atoms and an acid residue).

III. Learning new material.

Plan for studying new material “Slide No. 3”.

1. Hydrogen sulfide and sulfides.
2. Sulfurous acid and its salts.

1. Hydrogen sulfide and sulfides.

Today we will get acquainted with some of the acids that sulfur forms. In the last lesson, it was noted that the interaction of hydrogen and sulfur produces hydrogen sulfide. The reaction of hydrogen with all chalcogens occurs in exactly the same way. (H 2 O – H 2 S – H 2 Se – H 2 Te) “Slide No. 4-1”. Of these, only water is a liquid, the rest are gases, solutions of which will exhibit acidic properties. Like hydrogen halides, the strength of chalcohydrogen molecules decreases, and the strength of acids, on the contrary, increases “Slide No. 4-2”.

Hydrogen sulfide is a colorless gas with a pungent odor. It is very poisonous. It is the strongest reducing agent. As a reducing agent, it actively interacts with halogen solutions “Slide No. 5-1”:

H 2 + S -2 + I 2 0 = S 0 + 2H + I -

Hydrogen sulfide is burning “Slide No. 5-2”:

2H 2 S + O 2 = 2H 2 O + 2S (when the flame cools).

2H 2 S + 3O 2 = 2H 2 O + 2SO 2

When hydrogen sulfide is dissolved in water, weak hydrogen sulfide acid is formed [Demonstration of the effect of indicators on acid].

Sulfides of alkali and alkaline earth metals, as well as ammonium sulfide, are highly soluble and come in a variety of colors.

Exercise. Classify hydrogen sulfide acid (hydrogen sulfide is an oxygen-free, dibasic acid).

Thus, the dissociation of hydrosulfide acid occurs in steps “Slide No. 5-3”:

H2S<–>H + + HS - (first step of dissociation)

HS-<–>H + + S 2- (second stage of dissociation),

This means that hydrosulfide acid forms two types of salts:

hydrosulfides - salts in which only one hydrogen atom is replaced by a metal (NaHS)

sulfides are salts in which both hydrogen atoms (Na 2 S) are replaced by a metal.

2. Sulfurous acid and its salts.

Let's look at another acid that sulfur forms. We have already found out that when hydrogen sulfide burns, sulfur oxide (IV) is formed. It is a colorless gas with a characteristic odor. It exhibits the typical properties of acidic oxides and is highly soluble in water, forming a weak sulfurous acid [Demonstration of the action of indicators on acid]. It is not stable and decomposes into its original substances “Slide No. 6-1”:

H2O+SO2<–>H2SO3

Sulfur (IV) oxide can be obtained in different ways “Slide No. 6-2:

a) combustion of sulfur;
b) combustion of hydrogen sulfide;
c) common sulfides.

Sulfur(IV) oxide and sulfurous acid are typical reducing agents and at the same time weak oxidizing agents “Slide No. 7-1”. [Demonstration of the effect of acid on colored fabric].

Table 1. “Slide No. 7-2”

Oxidation states of sulfur in compounds.

Conclusion “Slide No. 8”. Restorative properties only reveal the elements found in lowest oxidation state .

Only oxidizing properties are exhibited by elements found in highest oxidation state .

Both reducing and oxidizing properties are exhibited by elements having intermediate oxidation state .

Exercise. Classify sulfurous acid (sulphurous is an oxygen-free, dibasic acid).

This means that sulfurous acid forms two types of salts:

hydrosulfites - salts in which only one hydrogen atom is replaced by a metal (NaHSO 3)

sulfites are salts in which both hydrogen atoms are replaced by a metal (Na 2 SO 3).

IV. Homework assignment

“Slide number 9” : § 23 (p. 134-140) ex. 1, 2, 5.

“Slide number 10.”

Literature

1. Gabrielyan O.S. Chemistry. 9th grade: educational. for general education institutions / O.S. Gabrielyan. – 14th ed., rev. – M.: Bustard, 2008. – 270, p. : ill.
2. Gabrielyan O.S. Desk book teachers. Chemistry. 9th grade / O.S. Gabrielyan, I.G. Ostroumov. – M.: Bustard, 2002. – 400 p.
3. Glinka N.L. general chemistry: Tutorial for universities / Ed. A.I. Ermakova. – ed. 30th, corrected - M.: Integral-Press, 2008. - 728 p.
4. Gorkovenko M.Yu. Chemistry. 9th grade. Lesson developments for textbooks by O.S. Gabrielyan (M.: Bustard);
5. Chemistry. – 2nd ed., revised. / ed. board: M. Aksyonov, I. Leenson, S. Martynova and others - M.: World of Avanta+ encyclopedias, Astrel, 2007. - 656 pp.: ill.

(Encyclopedia for children).

Lesson 22 9th grade Lesson on:Hydrogen sulfide. Sulfides. Sulfur oxide (IV

). Sulfurous acid Lesson objectives: General education:Hydrogen sulfide. Sulfides. Sulfur oxide (To consolidate students' knowledge on the topic covered: allotropy of sulfur and oxygen, the structure of sulfur and oxygen atoms, chemical properties and use of sulfur using testing, in order to prepare students for the State Examination; Study the structure, properties and use of gases: hydrogen sulfide, sulfur dioxide, sulfurous acid. Study salts - sulfides, sulfites and their qualitative determination using an electronic textbook in chemistry for grade 9. Study the influence of hydrogen sulfide, sulfur oxide (

) on the environment and human health. Use student presentations when learning a new topic and consolidating it. Use a multimedia projector when checking the test. Continue preparing students for passing chemistry exams in the form of State Examinations. Educational:

Moral and aesthetic education of students towards the environment. Fostering confidence in the positive role of chemistry in the life of modern society, the need for a chemically literate attitude towards one’s health and the environment. Developing the ability to work in pairs during self-analysis of control sections and tests. Educational: Be able to apply acquired knowledge to explain a variety of chemical phenomena and properties of substances. Be able to apply additional material from information sources, computer technologies when preparing students for the State Examination. Use acquired knowledge and skills in practical activities and Everyday life : a) environmentally conscious behavior in the environment; b) assessing the impact of chemical pollution environment

on the human body. Equipment for the lesson:Hydrogen sulfide. Sulfides. Sulfur oxide (G.E. Rudzitis, F.G. Feldman "Chemistry textbook 9th grade." Student presentations: “Hydrogen sulfide”, “Sulfur oxide (

)", "Ozone". Test for preparing the State Examination Test, answers to the test. Electronic manual for studying chemistry, grade 9: a) qualitative reactions to sulfide ion, sulfite ion. b) multimedia projector

c) projection screen. Protection of the poster “Environmental pollution by emissions of hydrogen sulfide and sulfur dioxide.”

During the classes.I

. Beginning of the lesson: The teacher announces the topic, purpose and objectives of the lesson.

Consolidation of the studied material:

It is carried out on test questions in order to prepare students for passing the State Examination Test (test attached).

Students mutually check the tests and give grades (the sheets are handed over to the teacher).Evaluation criteria: 0 errors – 5; 1 – 2 errors – 4; 3 errors – 3; 4 and more – 2

The test is carried out within 7 minutes and checked within 3 minutes.

II. Learning a new topic:

Hydrogen sulfide. Sulfides.

Hydrogen sulfide is a chemically valuable sulfur compound; we will study its properties in today’s lesson. We will get acquainted with the presence of hydrogen sulfide in nature, its physical properties and its effect on the human body and the environment through a presentation.

Why is it impossible to obtain hydrogen sulfide in the laboratory like other gases, for example: oxygen and hydrogen? Students will answer this question after listening to the presentation.

Structure of hydrogen sulfide:

a) molecular formula H 2 S -2 , oxidation state of sulfur (-2), toxic.

b) hydrogen sulfide has the smell of rotten eggs.

3. Preparation of hydrogen sulfide: Preparation in the laboratory: obtained by the action of dilute sulfuric acid on iron sulfide (II), since hydrogen sulfide is poisonous, experiments are carried out in a fume hood.H 2 + S 0 → H 2 S -2

FeS + H 2 SO 4 → FeSO 4 + H 2 Sthis reaction is carried out in a Kip apparatus, which is used to produce hydrogen.

4. Chemical properties hydrogen sulfide: Hydrogen sulfide burns in air with a blue flame and produces sulfur dioxide or sulfur oxide (Hydrogen sulfide. Sulfides. Sulfur oxide ()

2 H 2 S -2 + 3 O 2 → 2 H 2 O + 2 S +4 O 2

reducing agent

With a lack of oxygen, water and sulfur vapors are formed: 2H 2 S -2 + O 2 → 2 H 2 O + 2 S 0

Hydrogen sulfide has the properties of a reducing agent: if a small amount of bromine water is added to a test tube with hydrogen sulfide, the solution will become discolored and sulfur will appear on the surface of the solution

H 2 S -2 + Br 0 2 → S 0 + 2 HBr -1

Hydrogen sulfide is slightly soluble in water: in one volume of water att= 20 º 2.4 volumes of hydrogen sulfide dissolve, this solution is called hydrogen sulfide water or weak hydrogen sulfide acid. Consider the dissociation of hydrosulfide acid:H 2 S→ H + +HS -

H.S. - ↔ H + + S 2- Dissociation in the second step practically does not occur, since it is a weak acid. It gives 2 types of salts:

H.S. - (I)S 2-

hydrosulfides sulfides

During the classes.During the classes.During the classes.II

NaHSNa 2 S

Sodium hydrosulfide sodium sulfide

Hydrogen sulfide acid reacts with alkalis in a neutralization reaction:

H 2 S + NaOH → NaHS + H 2 O

excess

H 2 S+2NaOH→ Na 2 S+2H 2 O

excess

Qualitative reaction to sulfide ion (demonstration of experience from an electronic educational disk)

Pb(NO 3 ) 2 + Na 2 S → PbS↓ + 2 NaNO 3 write a complete ionic and a short one

black precipitate ionic equation

(Na 2 S + CuCl 2 → CuS↓ + 2 HCl)

black sediment

Exercise for the eyes. (1-2 minutes)

Compliance with sanitary and hygienic standards for working with a computer in the classroom.

5. Sulfur oxide( Hydrogen sulfide. Sulfides. Sulfur oxide () - sulphur dioxide.S +4 O 2 sulfur oxidation degree (+4).

Another important sulfur compound is sulfur oxide (Hydrogen sulfide. Sulfides. Sulfur oxide () SO 2 - sulphur dioxide. Poisonous.

We will get acquainted with the physical properties of sulfur dioxide, its application and impact on the environment and human health through a presentation.

Why sulfur dioxide cannot be obtained from practical work?

Obtaining sulfur oxide(Hydrogen sulfide. Sulfides. Sulfur oxide (): formed when sulfur burns in air, a gas with a pungent odor.

S+O 2 → SO 2

Sulfur dioxide has the properties of an acidic oxide; when dissolved in water, sulfurous acid is formed, an electrolyte of medium strength.SO 2 + H 2 O ↔ H 2 SO 3 litmus turns red.

Chemical propertiesSO 2 :

Reacts with basic oxidesSO 2 + CaO → CaSO 3

Reacts with alkalisSO 2 + 2 NaOH → Na 2 SO 3 + H 2 O

(at home, write down the complete ionic equation and the short ionic equation)

Sulfur exhibits oxidation states:S -2 , S 0 , S +4 , S +6 .

In sulfur oxide( Hydrogen sulfide. Sulfides. Sulfur oxide () SO 2 oxidation state +4, therefore sulfur dioxide exhibits the properties of an oxidizing agent and a reducing agent

S +4 O 2 + 2H 2 S -2 → 3S 0 ↓ + 2H 2 O S +4 O 2 + Cl 0 2 + 2H 2 O → H 2 S +6 O 4 + 2HCl -1 2-

Hydrosulfite sulfite

TO HSO 3 K 2 SO 3

Qualitative reaction to sulfite ion (the reagent is sulfuric acid, a gas with a pungent odor is formed that discolors solutions) fragment from an electronic educational disk.

K 2 SO 3 + H 2 SO 4 → K 2 SO 4 + SO 2 + H 2 O

At home, write down the complete and short ionic equation.

Protection of the poster “Environmental pollution with sulfur compounds.”

Protecting your presentation

Homework §11-12, notes, ex. 3.5 p.34(p)

III. Lesson summary:

The teacher sums up the lesson

Gives grades for tests and presentations.

Thanks students for the lesson.

First aid for gas poisoning: hydrogen sulfide, sulfur dioxide: rinsing the nose and mouth with 2% sodium bicarbonate solutionNaHCO 3 , peace, fresh air.

OVRs are specially highlighted in color in the article. Pay attention to them Special attention. These equations may appear on the Unified State Exam.

Dilute sulfuric acid behaves like other acids, hiding its oxidative capabilities:

And one more thing to remember about dilute sulfuric acid: she does not react with lead. A piece of lead thrown into dilute H2SO4 becomes covered with a layer of insoluble (see solubility table) lead sulfate and the reaction immediately stops.

Oxidizing properties of sulfuric acid

– heavy oily liquid, non-volatile, tasteless and odorless

Due to sulfur in the oxidation state +6 (higher), sulfuric acid acquires strong oxidizing properties.

Rule for task 24 (old A24) when preparing sulfuric acid solutions You should never pour water into it. Concentrated sulfuric acid should be poured into the water in a thin stream, stirring constantly.

Reaction of concentrated sulfuric acid with metals

These reactions are strictly standardized and follow the following scheme:

H2SO4(conc.) + metal → metal sulfate + H2O + reduced sulfur product.

There are two nuances:

1) Aluminum, iron And chromium with H2SO4 (conc) in normal conditions do not react due to passivation. Needs to be heated.

2) C platinum And gold H2SO4 (conc) does not react at all.

Sulfur V concentrated sulfuric acid- oxidizer

• This means that it will recover itself;
• the degree of oxidation to which sulfur is reduced depends on the metal.

Let's consider sulfur oxidation state diagram:

• Before -2 sulfur can only be reduced by very active metals - in a series of voltages up to and including aluminum.

The reactions will go like this:

8Li+5H 2 SO 4( conc. .) → 4Li 2 SO 4 + 4H 2 O+H 2 S

4Mg + 5H 2 SO 4( conc. .) → 4MgSO 4 + 4H 2 O+H 2 S

8Al + 15H 2 SO 4( conc. .) (t)→ 4Al 2 (SO 4 ) 3 +12H 2 O+3H 2 S

• upon interaction of H2SO4 (conc) with metals in a series of voltages after aluminum, but before iron, that is, with metals with average activity, sulfur is reduced to 0 :

3Mn + 4H 2 SO 4( conc. .) → 3MnSO 4 + 4H 2 O+S↓

2Cr + 4H 2 SO 4( conc. .) (t)→Cr 2 (SO 4 ) 3 + 4H 2 O+S↓

3Zn + 4H 2 SO 4( conc. .) → 3ZnSO 4 + 4H 2 O+S↓

• all other metals starting with hardware in a number of voltages (including those after hydrogen, except for gold and platinum, of course), they can only reduce sulfur to +4. Since these are low-active metals:

2 Fe + 6 H 2 SO 4(conc.) ( t)→ Fe 2 ( SO 4 ) 3 + 6 H 2 O + 3 SO 2

(note that iron oxidizes to +3, the highest possible oxidation state, since it is a strong oxidizing agent)

Cu+2H 2 SO 4( conc. .) → CuSO 4 + 2H 2 O+SO 2

2Ag + 2H 2 SO 4( conc. .) → Ag 2 SO 4 + 2H 2 O+SO 2

Of course, everything is relative. The depth of recovery will depend on many factors: acid concentration (90%, 80%, 60%), temperature, etc. Therefore, it is impossible to predict products completely accurately. The above table also has its own approximate percentage, but you can use it. It is also necessary to remember that in the Unified State Examination, when the product of reduced sulfur is not indicated and the metal is not particularly active, then, most likely, the compilers mean SO 2. You need to look at the situation and look for clues in the conditions.

SO 2 - this is generally a common product of ORR with the participation of conc. sulfuric acid.

H2SO4 (conc) oxidizes some nonmetals(which exhibit reducing properties), as a rule, to a maximum - the highest degree of oxidation (an oxide of this non-metal is formed). In this case, sulfur is also reduced to SO 2:

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

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

Freshly formed phosphorus oxide (V) reacts with water to produce orthophosphoric acid. Therefore, the reaction is recorded immediately:

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

The same thing with boron, it turns into orthoboric acid:

2B+3H 2 SO 4( conc. ) → 2H 3 B.O. 3 +3SO 2

The interaction of sulfur with an oxidation state of +6 (in sulfuric acid) with “other” sulfur (located in a different compound) is very interesting. Within the framework of the Unified State Examination, the interaction of H2SO4 (conc) is considered with sulfur (a simple substance) and hydrogen sulfide.

Let's start with interaction sulfur (a simple substance) with concentrated sulfuric acid. In a simple substance the oxidation state is 0, in an acid it is +6. In this ORR, sulfur +6 will oxidize sulfur 0. Let's look at the diagram of the oxidation states of sulfur:

Sulfur 0 will oxidize, and sulfur +6 will be reduced, that is, lower the oxidation state. Sulfur dioxide will be released:

2 H 2 SO 4(conc.) + S → 3 SO 2 + 2 H 2 O

But in the case of hydrogen sulfide:

Both sulfur (a simple substance) and sulfur dioxide are formed:

H 2 SO 4( conc. .) +H 2 S → S↓ + SO 2 + 2H 2 O

This principle can often help in determining the product of ORR, where the oxidizing and reducing agent are the same element, in different degrees oxidation. The oxidizing agent and the reducing agent “meet each other halfway” according to the oxidation state diagram.

H2SO4 (conc), one way or another, interacts with halides. Only here you need to understand that fluorine and chlorine are “themselves with a mustache” and ORR does not occur with fluorides and chlorides, undergoes a conventional ion exchange process during which hydrogen halide gas is formed:

CaCl 2 + H 2 SO 4 (conc.) → CaSO 4 + 2HCl

CaF 2 + H 2 SO 4 (conc.) → CaSO 4 + 2HF

But the halogens in the composition of bromides and iodides (as well as in the composition of the corresponding hydrogen halides) are oxidized to free halogens. Only sulfur is reduced in different ways: iodide is a stronger reducing agent than bromide. Therefore, iodide reduces sulfur to hydrogen sulfide, and bromide to sulfur dioxide:

2H 2 SO 4( conc. .) + 2NaBr → Na 2 SO 4 + 2H 2 O+SO 2 +Br 2

H 2 SO 4( conc. .) + 2HBr → 2H 2 O+SO 2 +Br 2

5H 2 SO 4( conc. .) + 8NaI → 4Na 2 SO 4 + 4H 2 O+H 2 S+4I 2 ↓

H 2 SO 4( conc. .) + 8HI → 4H 2 O+H 2 S+4I 2 ↓

Hydrogen chloride and hydrogen fluoride (as well as their salts) are resistant to the oxidizing action of H2SO4 (conc).

And finally, the last thing: this is unique for concentrated sulfuric acid, no one else can do this. She has water-removing property.

This allows concentrated sulfuric acid to be used in a variety of ways:

First, drying of substances. Concentrated sulfuric acid removes water from the substance and it “becomes dry.”

Secondly, a catalyst in reactions in which water is eliminated (for example, dehydration and esterification):

H 3 C–COOH + HO–CH 3 (H 2 SO 4 (conc.)) → H 3 C–C(O)–O–CH 3 + H 2 O

H 3 C–CH 2 –OH (H 2 SO 4 (conc.)) → H 2 C =CH 2 + H 2 O

Hydrogen sulfide (H₂S) is a colorless gas with a rotten egg odor. It is denser than hydrogen. Hydrogen sulfide is deadly poisonous to humans and animals. Even a small amount of it in the air causes dizziness and nausea, but the worst thing is that after inhaling it for a long time, this smell is no longer felt. However, for hydrogen sulfide poisoning, there is a simple antidote: you should wrap a piece of bleach in a handkerchief, then moisten it, and sniff the package for a while. Hydrogen sulfide is produced by reacting sulfur with hydrogen at a temperature of 350 °C:

H₂ + S → H₂S

This is a redox reaction: during it, the oxidation states of the elements participating in it change.

In laboratory conditions, hydrogen sulfide is produced by treating iron sulfide with sulfuric or hydrochloric acid:

FeS + 2HCl → FeCl₂ + H₂S

This is an exchange reaction: in it, the interacting substances exchange their ions. This process is usually performed using a Kipp apparatus.

Kipp apparatus

Properties of hydrogen sulfide

When hydrogen sulfide burns, sulfur oxide 4 and water vapor are formed:

2H₂S + 3О₂ → 2Н₂О + 2SO₂

H₂S burns with a bluish flame, and if you hold an inverted beaker over it, clear condensate (water) will appear on its walls.

However, with a slight decrease in temperature this reaction proceeds somewhat differently: a yellowish coating of free sulfur will appear on the walls of the pre-cooled glass:

2H₂S + O₂ → 2H₂O + 2S

The industrial method for producing sulfur is based on this reaction.

When a pre-prepared gaseous mixture of hydrogen sulfide and oxygen is ignited, an explosion occurs.

The reaction of hydrogen sulfide and sulfur(IV) oxide also produces free sulfur:

2H₂S + SO₂ → 2H₂O + 3S

Hydrogen sulfide is soluble in water, and three volumes of this gas can dissolve in one volume of water, forming weak and unstable hydrosulfide acid (H₂S). This acid is also called hydrogen sulfide water. As you can see, the formulas of hydrogen sulfide gas and hydrogen sulfide acid are written the same way.

If a solution of lead salt is added to hydrosulfide acid, a black precipitate of lead sulfide will form:

H₂S + Pb(NO₃)₂ → PbS + 2HNO₃

This is a qualitative reaction for the detection of hydrogen sulfide. It also demonstrates the ability of hydrosulfide acid to enter into exchange reactions with salt solutions. Thus, any soluble lead salt is a reagent for hydrogen sulfide. Some other metal sulfides also have a characteristic color, for example: zinc sulfide ZnS - white, cadmium sulfide CdS - yellow, copper sulfide CuS - black, antimony sulfide Sb₂S₃ - red.

By the way, hydrogen sulfide is an unstable gas and, when heated, almost completely decomposes into hydrogen and free sulfur:

H₂S → H₂ + S

Hydrogen sulfide interacts intensively with aqueous solutions halogens:

H₂S + 4Cl₂ + 4H₂O→ H₂SO₄ + 8HCl

Hydrogen sulfide in nature and human activity

Hydrogen sulfide is part of volcanic gases, natural gas and gases associated with oil fields. There is a lot of it in natural mineral waters, for example, in the Black Sea it lies at a depth of 150 meters and below.

Hydrogen sulfide is used:

• in medicine (treatment with hydrogen sulfide baths and mineral waters);
• in industry (production of sulfur, sulfuric acid and sulfides);
• in analytical chemistry (for the precipitation of heavy metal sulfides, which are usually insoluble);
• in organic synthesis (to produce sulfur analogues of organic alcohols (mercaptans) and thiophene (sulphur-containing aromatic hydrocarbon). Another recently emerging area in science is hydrogen sulfide energy. The production of energy from hydrogen sulfide deposits from the bottom of the Black Sea is being seriously studied.

The nature of redox reactions of sulfur and hydrogen

The reaction of hydrogen sulfide formation is redox:

Н₂⁰ + S⁰→ H₂⁺S²⁻

The process of interaction of sulfur with hydrogen is easily explained by the structure of their atoms. Hydrogen occupies first place in the periodic table, therefore, the charge of its atomic nucleus is equal to (+1), and 1 electron circles around the atomic nucleus. Hydrogen easily gives up its electron to atoms of other elements, turning into a positively charged hydrogen ion - a proton:

Н⁰ -1е⁻= Н⁺

Sulfur is in position sixteen in the periodic table. This means that the charge of the nucleus of its atom is (+16), and the number of electrons in each atom is also 16e⁻. The location of sulfur in the third period suggests that its sixteen electrons swirl around the atomic nucleus, forming 3 layers, the last of which contains 6 valence electrons. The number of valence electrons of sulfur corresponds to the number of group VI in which it is located in the periodic table.

So, sulfur can donate all six valence electrons, as in the case of the formation of sulfur(VI) oxide:

2S⁰ + 3O2⁰ → 2S⁺⁶O₃⁻²

In addition, as a result of the oxidation of sulfur, 4e⁻ can be given up by its atom to another element to form sulfur(IV) oxide:

S⁰ + O2⁰ → S⁺4 O2⁻²

Sulfur can also donate two electrons to form sulfur(II) chloride:

S⁰ + Cl2⁰ → S⁺² Cl2⁻

In all three of the above reactions, sulfur donates electrons. Consequently, it is oxidized, but at the same time acts as a reducing agent for oxygen atoms O and chlorine Cl. However, in the case of the formation of H2S, oxidation is the lot of hydrogen atoms, since they are the ones who lose electrons, restoring the external energy level of sulfur from six electrons to eight. As a result, each hydrogen atom in its molecule becomes a proton:

Н2⁰-2е⁻ → 2Н⁺,

and the sulfur molecule, on the contrary, being reduced, turns into a negatively charged anion (S⁻²): S⁰ + 2е⁻ → S⁻²

Thus, in the chemical reaction of hydrogen sulfide formation, it is sulfur that acts as an oxidizing agent.

From the point of view of the manifestation of sulfur in various oxidation states, another interesting interaction between sulfur(IV) oxide and hydrogen sulfide is the reaction to produce free sulfur:

2H₂⁺S-²+ S⁺⁴О₂-²→ 2H₂⁺O-²+ 3S⁰

As can be seen from the reaction equation, both the oxidizing agent and the reducing agent in it are sulfur ions. Two sulfur anions (2-) donate two of their electrons to the sulfur atom in the sulfur(II) oxide molecule, as a result of which all three sulfur atoms are reduced to free sulfur.

2S-² - 4е⁻→ 2S⁰ - reducing agent, oxidizes;

S⁺⁴ + 4е⁻→ S⁰ - oxidizing agent, reduced.