Hydrogen sulfide (H₂S) is colorless gas with the smell of rotten eggs. It is denser than hydrogen. Hydrogen sulfide is deadly poisonous to humans and animals. Even its slight content in the air causes dizziness and nausea, but the worst thing is that with prolonged inhalation, 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 scarf, then moisten it, and sniff this bundle for some time. 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 involved in it change.

Under laboratory conditions, hydrogen sulfide is produced by the action of sulfuric or hydrochloric acid on iron sulfide:

FeS + 2HCl → FeCl₂ + H₂S

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

Kipp apparatus

Properties of hydrogen sulfide

During the combustion of hydrogen sulfide, 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, a transparent condensate (water) will appear on its walls.

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

2H₂S + О₂ → 2Н₂О + 2S

This reaction is based on the industrial method of obtaining sulfur.

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

The reaction of hydrogen sulfide and sulfur oxide (IV) also allows you to get 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 a weak and unstable hydrosulfide acid (H₂S). This acid is also called hydrogen sulfide water. As you can see, the formulas for gas-hydrogen sulfide and hydrosulfide acid are written the same way.

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

H₂S + Pb(NO₃)₂ → PbS + 2HNO₃

This is qualitative reaction to detect 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 of 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 occurs at a depth of 150 meters and below.

Hydrogen sulfide is used:

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

The nature of the redox reactions of sulfur and hydrogen

The reaction of formation of hydrogen sulfide is redox:

H₂⁰ + S⁰→ H₂⁺S²⁻

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

H⁰ -1e⁻= H⁺

Sulfur is in the sixteenth position in the periodic table. Hence, 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 indicates that its sixteen electrons circle around the atomic nucleus, forming 3 layers, the last of which has 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 system.

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

2S⁰ + 3O2⁰ → 2S⁺⁶O₃⁻²

In addition, as a result of the oxidation of sulfur, 4е⁻ can be given away by its atom to another element with the formation of sulfur oxide (IV):

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 fate of hydrogen atoms, since it is they 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:

H2⁰-2e⁻ → 2H⁺,

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

Thus, in chemical reaction sulfur is the oxidizing agent in the formation of hydrogen sulfide.

From the point of view of the manifestation of gray various degrees oxidation, interesting and another interaction of sulfur oxide (IV) and hydrogen sulfide - the reaction of obtaining 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 oxide molecule (II), as a result of which all three sulfur atoms are reduced to free sulfur.

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

S⁺⁴ + 4е⁻→ S⁰ - oxidant, is reduced.

If they say that he is weak, then a disease has come, or hunger, in general, adversity. In chemistry, things are different. Consider a weak hydrogen sulfide. It is weak not because it is ready to disintegrate, to perish, but, on the contrary, because of the unwillingness to dissociate.

This is the name given to the process of dissolution in water, separation into hydronium ion and anion. Hydrogen sulfide dissociates by only 0.011%, moreover, in two stages. On the first of them, the degree of decomposition does not exceed 0.005%.

So, it is quite resistant, "holds the blow." However, this is by human standards. In chemistry, things are different. Let's dive into her world by continuing to study the properties of hydrogen sulfide.

Properties of hydrosulfide acid

The heroine's resilience is relative. Not wanting to completely dissolve in water, the compound decomposes under the action of oxygen. It oxidizes hydrosulfide acid. Formula it looks like this: - H 2 S. H in it -, S -. So, the latter, during oxidation, “breaks out” of the formula. The connection breaks up.

In fact, hydrosulfide acid is an aqueous solution of gas. Hydrogen sulfide is known for its rotten egg smell and toxicity. the substance does not. There are no indicator papers that have been in hydrosulphuric acid. Property this is another pointer to the weakness of the connection. Strong color litmus in tones.

Characteristics of hydrosulfide acid is reduced not only to slow dissolution in water. Other reactions with the heroine of the article also pass slowly. In relation to the human character, this is rather laziness than weakness.

With metals, for example, a hydrogen sulfide solution reacts reluctantly. The explanation for this is the low concentration of positive hydrogen ions. Their deficiency is associated with a small degree of dissociation.

Of the metals, the heroine of the article interacts only with those that are up to H 2 in the voltage series. Such elements are capable of displacing hydrogen from solution. The interaction can lead to the formation hydrosulphuric acid salts.

It is completely insoluble in water. The response concerns sulfides. This is one of the types formed with the participation of a hydrogen sulfide compound. The second type is hydrosulfides. They are formed during the reaction with alkali and alkaline earth, soluble.

By interacting with alkaline earth metals, hydrogen sulfide reacts with alkalis. The heroine of the article acts as a reducer, that is, she gives away electrons. It turns out that the properties of the connection are typical for a weak type.

The other is ambiguous. Being a solution of poisonous hydrogen sulfide, the heroine of the article is only relatively dangerous. Due to the low concentration of the original substance, it becomes a medicine. Where and how it is used, we will tell in the next chapter.

The use of hydrosulfide acid

Dissociation of hydrosulfide acid to a solution of saturation in thousandths of a percent allows the use of the compound for medicinal purposes. They, as a rule, are organized at the places where groundwater containing hydrogen sulfide comes out. The smell of rotten eggs is tolerated for the sake of getting rid of skin ailments, rehabilitation of the system, and treatment of insomnia.

Hydrogen sulfide baths improve blood flow, which means they have a beneficial effect on the entire body. Moving faster through the vessels, the blood does not stagnate, more quickly supplies the organs with the elements they need. The metabolism is accelerated, leading to the purification of toxins. On the general effect of rejuvenation.

"On the face" used in direct meaning. Cosmetologists use hydrogen sulfide solution for lifting procedures. In addition to tightening, you can get rid of cellulite and acne. Local application of the solution has fewer contraindications than baths.

Doctors notice that hydrogen sulfide baths are not taken at home and, in general, indoors. The concentration of vapors emanating from water may exceed the permissible values.

In sanatoriums, they try to place pools under open sky. Hot springs. Therefore, swimming in them is pleasant even in winter. There are a number of hydrogen sulfide resorts, for example, near the city of Severobaikalsk.

Doctors supervising the guests recommend the heroine of the article also as a cure for ailments of the genitourinary system. True, pregnant and lactating procedures are contraindicated. But, for those who want to become a parent, hydrogen sulfide baths will not hurt.

In the west of the country, hydrogen sulfide is formed along the Black Sea shelf. True, there the compound is formed at a depth of about 150 meters, emerging as bubbles in shallow water.

If temporary procedures in a gas atmosphere are acceptable, then prolonged inhalation of hydrogen sulfide leads to the extinction of the ability to smell. This is the result of paralysis of the olfactory nerve.

How to recognize hydrosulphuric acid in the air at a low concentration, in the absence of an obvious smell? Will only help. She is also poisonous, but otherwise nothing. Wet in the reagent. In an atmosphere with a hydrogen sulfide content of at least 0.0000001%, the sheet will be covered with bloom.

Obtaining hydrosulfide acid

Since it is a solution of hydrogen sulfide, it is worth wondering how to obtain it. A popular way to use and sulfide. As the latter, natural minerals are taken. There are several sulfides in the bowels of the planet. The most famous, perhaps. Its formula: - FeS 2.

The reaction between sulfide and violent, with active evolution of gas. Accordingly, the interaction is carried out in isolated rooms, using protective clothing and clothing.

Industrialists often go the other way. Hydrogen sulfide is a by-product of many industries. It remains only to extract the substance from industrial gases, the purification of which, anyway, is the direct responsibility of enterprises.

Then, hydrogen sulfide is dissolved in water. The liquid is heated. This makes dissociation more successful. The heroine of the article is ready for use or sale. Let's find out the prices.

Hydrosulphuric acid price

Since in everyday life the heroine of the article is needed only for water procedures, the sales form of the compound is reduced to for hydrogen sulfide baths. Example: - Means "Matsesta". It is sold in pharmacies, like other drugs of the group.

"Matsesta" is sold in packages, added to a bath with water at a temperature of 37-38 degrees Celsius. The drug is thoroughly stirred and immersed for 5-15 minutes. The pleasure costs about 300 per package, that is, one procedure.

Nobody canceled the remark about the danger of taking hydrogen sulfide baths at home. But, manufacturers are reinsured, choosing the optimal, safe concentration. With her, do not apply for 15 minutes.

For laboratory needs and industrial production, it makes no sense to pay for water with a minimum proportion of hydrogen sulfide. It is more convenient to organize the supply of liquefied gas in cylinders and do it yourself. The product is specific, demand is limited. Therefore, there are few offers, and for gas cylinders, as a rule, it is negotiable.

When heated, sulfur reacts with hydrogen. A poisonous gas with a pungent odor is formed - hydrogen sulfide. In another way it is called hydrogen sulfide, hydrogen sulfide, dihydrosulfide.

Structure

Hydrogen sulfide is a binary compound of sulfur and hydrogen. The formula of hydrogen sulfide is H 2 S. The structure of the molecule is similar to the structure of the water molecule. However, sulfur forms with hydrogen not a hydrogen, but a covalent polar bond. This is due to the fact that, unlike the oxygen atom, the sulfur atom is larger in volume, has a lower electronegativity and a lower charge density.

Rice. 1. The structure of hydrogen sulfide.

Receipt

Hydrogen sulfide is rarely found in nature. In not high concentrations is part of associated, natural, volcanic gases. The seas and oceans contain hydrogen sulfide for great depths. For example, hydrogen sulfide is found at a depth of 200 meters in the Black Sea. In addition, hydrogen sulfide is released during the decay of proteins containing sulfur.

In industry, it is obtained in several ways:

• reaction of acids with sulfides:

  FeS + 2HCl → FeCl 2 + H 2 S;

• effect of water on aluminum sulfide:

  Al 2 S 3 + 6H 2 O → 2Al (OH) 3 + 3H 2 S;

• fusing sulfur with paraffin:

  C 18 H 38 + 18S → 18H 2 S + 18C.

The purest gas is obtained by direct interaction of hydrogen and sulfur. The reaction proceeds at 600°C.

Physical Properties

Dihydrosulfide is a colorless gas with a rotten egg odor and a sweetish taste. It is a poisonous substance, dangerous in high concentrations. Due to its molecular structure, hydrogen sulfide does not liquefy under normal conditions.

General physical properties of hydrogen sulfide:

• poorly soluble in water;
• exhibits the properties of a superconductor at a temperature of -70°C and a pressure of 150 GPa;
• flammable;
• soluble in ethanol;
• liquefies at -60.3°C;
• turns into a solid at -85.6°C;
• melts at -86°C;
• boils at -60°C;
• decomposes into simple substances (sulfur and hydrogen) at 400°C.

Under normal conditions, you can prepare a solution of hydrogen sulfide (hydrogen sulfide water). However, hydrogen sulfide does not react with water. In air, the solution quickly oxidizes and becomes cloudy due to the release of sulfur. Hydrogen sulfide water exhibits weak acid properties.

Rice. 2. Hydrogen sulfide water.

Chemical properties

Hydrogen sulfide is a powerful reducing agent. The main chemical properties of the substance are described in the table.

Reaction	Description	The equation
With oxygen	Burns in air with a blue flame to form sulfur dioxide. With a lack of oxygen, sulfur and water are formed	2H 2 S + 4O 2 → 2H 2 O + 2SO 2; 2H 2 S + O 2 → 2S + 2H 2 O
With oxidizers	Oxidizes to sulfur dioxide or sulfur	3H 2 S + 4HClO 3 → 3H 2 SO 4 + 4HCl; 2H 2 S + SO 2 → 2H 2 O + 3S; 2H 2 S + H 2 SO 3 → 3S + 3H 2 O
With alkalis	With an excess of alkali, medium salts are formed, with a ratio of 1: 1 - acidic	H 2 S + 2NaOH → Na 2 S + 2H 2 O; H 2 S + NaOH → NaHS + H 2 O
dissociations	Dissociates stepwise in solution	H 2 S ⇆ H + + HS – ; HS - ⇆ H + + S 2-
quality	Formation of a black precipitate - lead sulfide	H 2 S + Pb(NO 3) 2 → PbS↓ + 2HNO 3

Rice. 3. Combustion of hydrogen sulfide.

Hydrogen sulfide is a toxic gas, so its use is limited. Most of the produced hydrogen sulfide is used in industrial chemistry for the production of sulfur, sulfide, sulfuric acid.

What have we learned?

From the topic of the lesson, we learned about the structure, production and properties of hydrogen sulfide or hydrogen sulfide. It is a colorless gas with an unpleasant odor. It is a toxic substance. Forms hydrogen sulfide water without interacting with water. In reactions, it exhibits the properties of a reducing agent. Reacts with atmospheric oxygen, strong oxidizing agents (oxides, oxygen acids), with alkalis. Dissociates in solution in two stages. Hydrogen sulfide is used in chemical industry for the manufacture of derivatives.

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hydrogen sulfide (H 2 S) is a highly carcinogenic, toxic gas. It has a strong characteristic smell of rotten eggs.

Getting hydrogen sulfide.

1. In the laboratory H 2 S obtained during the reaction between sulfides and dilute acids:

FeS + 2 HCl = FeCl 2 + H 2 S,

2. Interaction Al 2 S 3 with cold water (the resulting hydrogen sulfide is more pure than in the first method of production):

Al 2 S 3 + 6H 2 O \u003d 2Al (OH) 3 + 3H 2 S.

Chemical properties of hydrogen sulfide.

hydrogen sulfide H 2 S - a covalent compound that does not form hydrogen bonds, like a molecule H 2 O. (The difference is that the sulfur atom is larger and more electronegative than the oxygen atom. Therefore, the charge density of sulfur is lower. And due to the lack of hydrogen bonds, the boiling point of H 2 S higher than that of oxygen. Also H 2 S poorly soluble in water, which also indicates the absence of hydrogen bonds).

H 2 S + Br 2 \u003d S + 2HBr,

2. Hydrogen sulfide H 2 S- very weak acid, dissociates stepwise in solution:

H 2 S ⇆ H + + HS - ,

HS - ⇆ H + + S 2- ,

3. Interacts with strong oxidizing agents:

H 2 S + 4Cl 2 + 4H 2 O \u003d H 2 SO 4 + 8HCl,

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

2 FeCl 3 + H 2 S = 2 FeCl 2 + S + 2 HCl,

4. Reacts with bases, basic oxides and salts, while forming acidic and medium salts (hydrosulfides and sulfides):

Pb(NO 3) 2 + 2S = PbS↓ + 2HNO 3 .

This reaction is used to detect hydrogen sulfide or sulfide ions. PbS- Black sediment.

The chemical structure of H 2 S molecules is similar to the structure of H 2 O molecules: (angular shape)

But, unlike water, H 2 S molecules are of low polarity; hydrogen bonds between them are not formed; the strength of the molecules is much lower.

Physical Properties

At normal temperature, H 2 S is a colorless gas with an extremely unpleasant suffocating smell of rotten eggs, very poisonous (at a concentration> 3 g / m 3 causes fatal poisoning). Hydrogen sulfide is heavier than air, easily condenses into a colorless liquid. H 2 S is soluble in water (at normal temperature, 2.5 liters of gas dissolve in 1 liter of H 2 O).

Hydrogen sulfide in nature

H 2 S is present in volcanic and underground gases, in the water of sulfur sources. It is formed during the decay of proteins containing sulfur, and is also released during the vital activity of numerous microorganisms.

How to get

1. Synthesis from simple substances:

S + H 2 \u003d H 2 S

2. Action of non-oxidizing acids on metal sulfides:

FeS + 2HCI \u003d H 2 S + FeCl 2

3. Action conc. H 2 SO 4 (without excess) into alkaline and alkaline earth Me:

5H 2 SO 4 (conc.) + 8Na \u003d H 2 S + 4Na 2 SO 4 + 4H 2 O

4. It is formed during the irreversible hydrolysis of some sulfides:

AI 2 S 3 + 6H 2 O \u003d 3H 2 S + 2Al (OH) 3 ↓

Chemical properties of H 2 S

H 2 S - strong reducing agent

The interaction of H 2 S with oxidizing agents leads to the formation of various substances (S, SO 2, H 2 SO 4),

Reactions with simple substances oxidizers

Air oxygen oxidation

2H 2 S + 3O 2 (excess) \u003d 2SO 2 + 2H 2 O

2H 2 S + O 2 (deficiency) \u003d 2S ↓ + 2H 2 O

Oxidation with halogens:

H 2 S + Br 2 = S↓ + 2НВr

Reactions with oxidizing acids (HNO 3 , H 2 SO 4 (conc.).

3H 2 S + 8HNO 3 (razb.) \u003d 3H 2 SO 4 + 8NO + 4H 2 O

H 2 S + 8HNO 3 (conc.) \u003d H 2 SO 4 + 8NO 2 + 4H 2 O

H 2 S + H 2 SO 4 (conc.) \u003d S ↓ + SO 2 + 2H 2 O

Reactions with salts - oxidizing agents

5H 2 S + 2KMnO 4 + 3H 2 SO 4 = 5S↓ + 2MnSO 4 + K 2 SO 4 + 8H 2 O

5H 2 S + 6KMnO 4 + 9H 2 SO 4 = 5SO 2 + 6MnSO 4 + 3K 2 SO 4 + 14H 2 O

H 2 S + 2FeCl 3 = S↓ + 2FeCl 2 + 2HCl

An aqueous solution of H 2 S exhibits the properties of a weak acid

Hydrosulfide acid H 2 S 2-basic acid dissociates in steps

1st stage: H 2 S → H + + HS -

2nd stage: HS - → H + + S 2-

H 2 S in aqueous solution is characterized by reactions common to a class of acids, in which it behaves like a weak acid. Interacts:

a) with active metals

H 2 S + Mg \u003d H 2 + MgS

b) with low-active metals (Ag, Cu, Hg) in the presence of oxidizing agents

2H 2 S + 4Аg + O 2 = 2Ag 2 S↓ + 2Н 2 O

c) with basic oxides

H 2 S + BaO \u003d BaS + H 2 O

d) with alkalis

H 2 S + NaOH (lack) = NaHS + H 2 O

e) with ammonia

H 2 S + 2NH 3 (excess) = (NH 4) 2 S

Features of the reactions of H 2 S with salts of strong acids

Despite the fact that hydrosulfide acid is very weak, it reacts with some salts of strong acids, for example:

CuSO 4 + H 2 S \u003d CuS ↓ + H 2 SO 4

Reactions proceed in cases where the resulting Me sulfide is insoluble not only in water, but also in strong acids.

Qualitative reaction to the sulfide anion

One of these reactions is used to detect S 2- anions and hydrogen sulfide:

H 2 S + Pb(NO 3) 2 = 2HNO 3 + PbS ↓ black precipitate.

Gaseous H 2 S is detected using wet paper soaked in Pb(NO 3) 2 solution, which turns black in the presence of H 2 S.

Sulfides

Sulfides are binary sulfur compounds with less EO elements, including some non-metals (C, Si, P, As, etc.).

Metal sulfides are of the greatest importance, since many of them are natural compounds and are used as raw materials for the production of free metals, sulfur, and sulfur dioxide.

Reversible hydrolysis of soluble sulfides

Alkaline Me and ammonium sulfides are highly soluble in water, but in aqueous solution they undergo hydrolysis to a very large extent:

S 2- + H 2 O → HS - + OH -

Therefore, sulfide solutions have a strongly alkaline reaction

Sulfides of alkaline earth Me and Mg, interacting with water, undergo complete hydrolysis and become soluble acid salts- hydrosulfides:

2CaS + 2HOH \u003d Ca (HS) 2 + Ca (OH) 2

When sulfide solutions are heated, hydrolysis also proceeds in the 2nd stage:

HS - + H 2 O → H 2 S + OH -

Irreversible hydrolysis of sulfides

Sulfides of some metals undergo irreversible hydrolysis and completely decompose into aqueous solutions, For example:

Al 2 S 3 + 6H 2 O \u003d 3H 2 S + 2AI (OH) 3 ↓

Cr 2 S 3, Fe 2 S 3 decompose in a similar way

Insoluble sulfides

Most heavy metal sulfides are practically insoluble in water and therefore do not undergo hydrolysis. Some of them dissolve under the action of strong acids, for example:

FeS + 2HCI \u003d FeCl 2 + H 2 S

ZnS + 2HCI \u003d ZnCl 2 + H 2 S

Sulfides Ag 2 S, HgS, Hg 2 S, PbS, CuS are insoluble not only in water, but also in many acids.

Oxidative roasting of sulphides

Oxidation of sulfides by atmospheric oxygen at high temperature is an important stage in the processing of sulfide raw materials. Examples:

2ZnS + 3O 2 = 2ZnO + 2SO 2

4FeS 2 + 11O 2 = 2Fe 2 O 3 + 8SO 2

Methods for obtaining sulfides

1. Direct connection of simple substances:

2. Interaction of H 2 S with alkali solutions:

H 2 S + 2NaOH \u003d 2H 2 O + Na 2 S sodium sulfide

H 2 S + NaOH = H 2 O + NaHS sodium hydrosulfide

3. Interaction of H 2 S or (NH 4) 2 S with salt solutions:

H 2 S + CuSO 4 \u003d CuS ↓ + H 2 SO 4

H 2 S + 2AgNO 3 \u003d Ag2S ↓ + 2HNO 3

4. Recovery of sulfates by calcination with coal:

Na 2 SO 4 + 4C \u003d Na 2 S + 4CO

This process is used to produce alkali and alkaline earth metal sulfides.