Hydrosulfuric acid graphic formula. Hydrogen sulfide and hydrosulphuric acid. Salts of hydrosulphuric acid (sulfides), their solubility in water and interaction with mineral acids. What is hydrogen sulfide

An aqueous solution of H 2 S (the formula of hydrogen sulfide acid) is otherwise called hydrogen sulfide water or hydrosulfide acid. This is one of the weakest mineral acids (indicators in it do not change their color), it dissociates in 2 stages:

H 2 S -- H + + HS - K 1 diss. ≈ 6 ∙ 10 -8

HS - -- H + + S 2- K 2 diss. ≈ 1 ∙ 10 -14

Solutions of hydrosulfide acid are dilute, their maximum molar concentration at 20 o C and atmospheric pressure does not exceed 0.12 mol/l, and the degree of dissociation in the first stage is ~ 0.011%.

Hydrosulphuric acid can react with metals standing in a series of voltages up to H 2, showing oxidizing properties due to H + ions. But such reactions proceed very slowly under normal conditions due to the low concentration of H + ions in the solution and, mainly, on the surface of the metal, because most salts of hydrosulfide acid are insoluble in H 2 O. Similarly, H 2 S reacts with metal oxides, insoluble hydroxides.

Insoluble Mediums hydrosulphuric acid salts(sulfides) are obtained by the interaction of sulfur with metals or in exchange reactions between salt solutions:

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

K 2 S + FeCl 2 = FeS↓ + 2KCl

Soluble sulfides formed by alkali and alkaline earth metals. They can be obtained by the interaction of acid solutions with metals or alkalis. In this case, depending on the molar ratio between the starting materials, both acidic (hydrosulfides) and medium salts can be formed.

H 2 S + NaOH \u003d NaHS + H 2 O (with a lack of alkali)

H 2 S + 2NaOH \u003d Na 2 S + 2H 2 O (in excess alkali)

In aqueous solutions, medium salts are strongly hydrolyzed:

Na 2 S + HOH -- NaHS + NaOH

S 2- + HOH -- HS - + OH -

therefore their solutions have an alkaline reaction.

Sulfides alkaline earth metals in an aqueous solution, according to the first stage, they are almost 100% hydrolyzed and exist in the form of soluble acid salts:

2CaS + 2HOH = Ca(HS) 2 + Ca(OH) 2

Sulfides of some metals (Al 2 S 3, Fe 2 S 3, Cr 2 S 3) in H 2 O are completely hydrolyzed:

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

Most heavy metal sulfides are very poorly soluble in H2O.

Some sulfides (CuS, HgS, Ag 2 S, PbS) are not decomposed by solutions of strong acids. Therefore, hydrosulfide acid can displace strong acids from aqueous solutions of their salts formed by these metals:

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

HgCl 2 + H 2 S \u003d HgS ↓ + 2HCl

Hydrosulfuric acid in air is slowly oxidized by oxygen with the release of sulfur:

2H 2 S + O 2 \u003d 2S ↓ + 2H 2 O

Therefore, over time, H 2 S solutions become cloudy during storage.

Thanks to this reaction, hydrogen sulfide does not accumulate in the upper layers of the Black Sea water, which contain a lot of dissolved oxygen.

Hydrosulfide acid, like hydrogen sulfide, is a strong reducing agent and is oxidized by the same oxidizing agents as H 2 S, with the formation of similar products.

Heavy metal sulfides have various bright colors and are used to obtain mineral paints used in painting.

An important property of sulfides is their oxidation with oxygen during roasting. This reaction is used in metallurgy to obtain non-ferrous metals from sulfide ores:

2CuS + 3O 2 -- 2CuO + 2SO 2

During the firing of active metal sulfides, the resulting SO 2 and metal oxide can react with each other to form salts of sulfurous acid.

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 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 obtained 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 usually carried out using the 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 hydrogen sulfide gas and hydrosulfide acid are written in 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 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 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, the charge of its atomic nucleus is (+1), and 1 electron circles around the nucleus of the 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 the chemical reaction of the formation of hydrogen sulfide, it is sulfur that acts as an oxidizing agent.

From the point of view of the manifestation of various oxidation states by sulfur, another interaction of sulfur oxide (IV) and hydrogen sulfide is also interesting - 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.

Physical properties

Gas, colorless, with the smell of rotten eggs, poisonous, soluble in water (in 1 V H 2 O dissolves 3 V H 2 S at n.o.); t °pl. = -86° C ; t °bp = -60°С.

The effect of hydrogen sulfide on the body:

Hydrogen sulfide not only smells bad, it is also extremely toxic. When this gas is inhaled in large quantities, paralysis of the respiratory nerves quickly sets in, and then the person ceases to smell - this is the mortal danger of hydrogen sulfide.

There are many cases of poisoning with harmful gas when workers were injured while repairing pipelines. This gas is heavier, so it accumulates in pits, wells, from which it is not so easy to get out quickly.

Receipt

1) H 2 + S → H 2 S (at t)

2) FeS + 2 HCl → FeCl 2 + H 2 S

Chemical properties

1) Solution H 2 S in water it is a weak dibasic acid.

Dissociation occurs in two stages:

H 2 S → H + + HS - (first stage, hydrosulfide ion is formed)

HS - → 2 H + + S 2- (second step)

Hydrosulfuric acid forms two series of salts - medium (sulfides) and acidic (hydrosulfides):

Na 2 S- sodium sulfide;

CaS– calcium sulfide;

NaHS– sodium hydrosulfide;

Ca( HS) 2 – calcium hydrosulfide.

2) Interacts with bases:

H 2 S + 2 NaOH (excess) → Na 2 S + 2 H 2 O

H 2 S (excess) + NaOH → Na H S + H 2 O

3) H 2 S exhibits very strong restorative properties:

H 2 S -2 + Br 2 → S 0 + 2HBr

H 2 S -2 + 2FeCl 3 → 2FeCl 2 + S 0 + 2HCl

H 2 S -2 + 4Cl 2 + 4H 2 O → H 2 S +6 O 4 + 8HCl

3H 2 S -2 + 8HNO 3 (conc) → 3H 2 S +6 O 4 + 8NO + 4H 2 O

H 2 S -2 + H 2 S +6 O 4 (conc) → S 0 + S +4 O 2 + 2H 2 O

(when heated, the reaction proceeds in a different way:

H 2 S -2 + 3H 2 S +6 O 4 (conc) → 4S +4 O 2 + 4H 2 O

4) Hydrogen sulfide is oxidized:

with a lack O 2

2 H 2 S -2 + O 2 → 2 S 0 + 2 H 2 O

with an excess of O 2

2H 2 S -2 + 3O 2 → 2S +4 O 2 + 2H 2 O

5) Silver turns black on contact with hydrogen sulfide:

4 Ag + 2 H 2 S + O 2 → 2 Ag 2 S ↓ + 2 H 2 O

Darkened objects can be restored to shine. To do this, they are boiled in an enameled bowl with a solution of soda and aluminum foil. Aluminum reduces silver to metal, and the soda solution retains sulfur ions.

6) Qualitative reaction to hydrogen sulfide and soluble sulfides - formation of a dark brown (almost black) precipitate PbS:

H 2 S + Pb(NO 3) 2 → PbS↓ + 2HNO 3

Na 2 S + Pb(NO 3) 2 → PbS↓ + 2NaNO 3

Pb 2+ + S 2- → PbS ↓

Atmospheric pollution causes blackening of the surface of paintings painted with oil paints, which include white lead. One of the main reasons for the darkening of the artistic paintings of the old masters was the use of white lead, which, over several centuries, interacting with traces of hydrogen sulfide in the air (formed in small quantities during the decay of proteins; in the atmosphere of industrial regions, etc.) turns into PbS. White lead is a pigment that is lead carbonate ( II). It reacts with hydrogen sulfide found in the polluted atmosphere to form lead sulfide ( II), black compound:

PbCO 3 + H 2 S = PbS↓ + CO 2 + H 2 O

When processing lead sulfide ( II) hydrogen peroxide reaction occurs:

PbS + 4 H 2 O 2 = PbSO 4 + 4 H 2 O,

this forms lead sulfate ( II), a white compound.

Thus, blackened oil paintings are restored.

7) Restoration:

PbS + 4 H 2 O 2 → PbSO 4 (white) + 4 H 2 O

Sulfides

Getting sulfides

1) Many sulfides are obtained by heating a metal with sulfur:

Hg + S → HgS

2) Soluble sulfides are obtained by the action of hydrogen sulfide on alkalis:

H 2 S + 2 KOH → K 2 S + 2 H 2 O

3) Insoluble sulfides are obtained by exchange reactions:

CdCl 2 + Na 2 S → 2NaCl + CdS↓

Pb(NO 3) 2 + Na 2 S → 2NaNO 3 + PbS↓

ZnSO 4 + Na 2 S → Na 2 SO 4 + ZnS↓

MnSO 4 + Na 2 S → Na 2 SO 4 + MnS↓

2SbCl 3 + 3Na 2 S → 6NaCl + Sb 2 S 3 ↓

SnCl 2 + Na 2 S → 2NaCl + SnS↓

Chemical properties of sulfides

1) Soluble sulfides are highly hydrolyzed, as a result of which their aqueous solutions have an alkaline reaction:

K 2 S + H 2 O → KHS + KOH

S 2- + H 2 O → HS - + OH -

2) Sulfides of metals that are in the series of voltages to the left of iron (inclusive) are soluble in strong acids:

ZnS + H 2 SO 4 → ZnSO 4 + H 2 S

3) Insoluble sulfides can be converted into a soluble state by the action of concentrated HNO 3 :

FeS 2 + 8HNO 3 → Fe(NO 3) 3 + 2H 2 SO 4 + 5NO + 2H 2 O

TASKS FOR REINFORCEMENT

Task number 1
Write the reaction equations that can be used to carry out the following transformations:
Cu→ CuS→ H 2 S→ SO2

Task number 2
Make the equations of redox reactions of complete and incomplete combustion of hydrogen sulfide. Arrange the coefficients using the electron balance method, indicate the oxidizing agent and reducing agent for each reaction, as well as the oxidation and reduction processes.

Task number 3
Write the equation for the chemical reaction of hydrogen sulfide with a solution of lead (II) nitrate in molecular, full and short ionic form. Mark the signs of this reaction, is the reaction reversible?

Task number 4

Hydrogen sulfide was passed through an 18% solution of copper (II) sulfate weighing 200 g. Calculate the mass of the precipitate resulting from this reaction.

Task number 5
Determine the volume of hydrogen sulfide (n.o.) formed during the interaction of hydrochloric acid with a 25% solution of iron (II) sulfide weighing 2 kg?

Sulfur is one of the substances known to mankind from time immemorial. Even the ancient Greeks and Romans found various uses for it. Pieces of native sulfur were used to perform the rite of expelling evil spirits. So, according to legend, Odysseus, returning to native home after long wanderings, the first thing he ordered was to fumigate it with sulfur. There are many references to this substance in the Bible.

In the Middle Ages, sulfur occupied an important place in the arsenal of alchemists. As they believed, all metals are composed of mercury and sulfur: the less sulfur, the more noble. Practical interest in this substance in Europe increased in the XIII-XIV centuries, after the advent of gunpowder and firearms. Italy was the main supplier of sulfur.

Nowadays, sulfur is used as a raw material for the production of sulfuric acid, gunpowder, in the vulcanization of rubber, in organic synthesis, and also for pest control in agriculture. Sulfur powder is used in medicine as an external disinfectant.

The interaction of sulfur with simple substances

Sulfur reacts like oxidizing agent :

2Na + S = Na 2 S

how reducing agent :

The interaction of sulfur with complex substances

a) sulfur does not dissolve in water and is not even wetted by water;

b) how the reducing agent sulfur interacts with ( , ) when heated:

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

S + 2HNO 3 = H 2 SO 4 + 2NO

S + 6HNO 3 \u003d H 2 SO 4 + 6NO 2 + 2H 2 O

c) showing the properties of both an oxidizing agent and a reducing agent, sulfur enters into disproportionation reactions (self-oxidation-self-recovery) with solutions when heated:

3S + 6NaOH \u003d 2Na 2 S + Na 2 SO 3 + 3H 2 O

Hydrogen sulfide and hydrosulphuric acid

a) H 2 S + CaO \u003d CaS + H 2 O

b) H 2 S + NaOH = NaHS + H 2 O

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

d) Ca + H 2 S \u003d CaS + H 2

A qualitative reaction to hydrosulfide acid and its soluble salts (i.e., to the sulfide ion S 2-) is their interaction with soluble salts. In this case, a black precipitate of lead (II) sulfide PbS is released:

Na 2 S + Pb (NO 3) 2 \u003d PbS ↓ + 2NaNO 3

Redox properties

In redox reactions, both gaseous hydrogen sulfide and hydrosulfide acid exhibit strong reducing properties, since the sulfur atom in H 2 S has the lowest oxidation state - 2, and therefore can only be oxidized. It oxidizes easily:

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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 small concentrations, it is part of associated, natural, volcanic gases. Seas and oceans contain hydrogen sulfide at 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.

Are common physical properties 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 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. Main Chemical properties substances 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	The 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 the chemical industry for the manufacture of derivatives.

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