Hydrogen sulfide acid oxygen. Hydrogen sulfide. Hydrogen sulfide acid and its salts. Reactions with simple oxidizing substances

DEFINITION

Hydrogen sulfide is a colorless gas with a characteristic smell of rotting protein.

It is slightly heavier than air, liquefies at a temperature of -60.3 o C and solidifies at -85.6 o C. In air, hydrogen sulfide burns with a bluish flame, forming sulfur dioxide and water:

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

If you add some cold object to the hydrogen sulfide flame, for example a porcelain cup, then the flame temperature drops significantly and hydrogen sulfide is oxidized only to free sulfur, which settles on the cup in the form of a yellow bloom:

2H 2 S + O 2 = 2H 2 O + 2S.

Hydrogen sulfide is highly flammable; its mixture with air explodes. Hydrogen sulfide is very toxic. Long-term inhalation of air containing this gas, even in small quantities, causes severe poisoning.

At 20 o With one volume of water dissolves 2.5 volumes of hydrogen sulfide. A solution of hydrogen sulfide in water is called hydrogen sulfide water. When standing in the air, especially in the light, hydrogen sulfide water soon becomes cloudy from the emitted sulfur. This occurs as a result of the oxidation of hydrogen sulfide with atmospheric oxygen.

Hydrogen sulfide production

At high temperature sulfur reacts with hydrogen to form hydrogen sulfide gas.

In practice, hydrogen sulfide is usually obtained by the action of dilute acids on sulfurous metals, for example, on iron sulfide:

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

More pure hydrogen sulfide can be obtained by hydrolysis of CaS, BaS or A1 2 S 3. The purest gas is obtained by direct reaction of hydrogen and sulfur at 600 ° C.

Chemical properties of hydrogen sulfide

A solution of hydrogen sulfide in water has the properties of an acid. Hydrogen sulfide is a weak dibasic acid. It dissociates stepwise and mainly in the first step:

H 2 S↔H + + HS - (K 1 = 6 × 10 -8).

Dissociation in the second stage

HS - ↔H + + S 2- (K 2 = 10 -14)

proceeds in an negligible degree.

Hydrogen sulfide is a strong reducing agent. Under the action of strong oxidants, it is oxidized to sulfur dioxide or sulfuric acid; the depth of oxidation depends on the conditions: temperature, pH of the solution, concentration of the oxidizing agent. For example, the reaction with chlorine usually proceeds to form sulfuric acid:

H 2 S + 4Cl 2 + 4H 2 O = H 2 SO 4 + 8HCl.

Medium salts of hydrogen sulfide are called sulfides.

Application of hydrogen sulfide

The use of hydrogen sulfide is rather limited, which is primarily due to its high toxicity. It has found application in laboratory practice as a precipitant heavy metals... Hydrogen sulfide serves as a raw material for the production of sulfuric acid, sulfur in its elemental form and sulfides

Examples of problem solving

EXAMPLE 1

The task	Determine how many times the hydrogen sulfide H 2 S is heavier than air.
Solution	The ratio of the mass of a given gas to the mass of another gas taken in the same volume, at the same temperature and the same pressure, is called the relative density of the first gas over the second. This value shows how many times the first gas is heavier or lighter than the second gas. Relative molecular weight air is taken equal to 29 (taking into account the content of nitrogen, oxygen and other gases in the air). It should be noted that the concept of "relative molecular weight of air" is used conventionally, since air is a mixture of gases. D air (H 2 S) = M r (H 2 S) / M r (air); D air (H 2 S) = 34/29 = 1.17. M r (H 2 S) = 2 × A r (H) + A r (S) = 2 × 1 + 32 = 2 + 32 = 34.
Answer	Hydrogen sulfide H 2 S is 1.17 times heavier than air.

EXAMPLE 2

The task	Find the hydrogen density of a gas mixture in which the volume fraction of oxygen is 20%, hydrogen is 40%, the rest is hydrogen sulfide H 2 S.
Solution	The volume fractions of gases will coincide with the molar ones, i.e. with fractions of quantities of substances, this is a consequence of Avogadro's law. Let's find the conditional molecular weight of the mixture: M r conditional (mixture) = φ (O 2) × M r (O 2) + φ (H 2) × M r (H 2) + φ (H 2 S) × M r (H 2 S);

Hydrogen sulfide (H₂S) is a colorless gas that smells like rotten eggs. It is heavier than hydrogen in density. Hydrogen sulfide is deadly poisonous to humans and animals. Even its insignificant content in the air causes dizziness and nausea, but the worst thing is that with prolonged inhalation, this smell is no longer felt. However, in case of hydrogen sulfide poisoning, there is a simple antidote: a piece of bleach should be wrapped in a handkerchief, then moistened, and sniffed for a while. Hydrogen sulfide is produced by the interaction of 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 obtained by acting on 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 usually performed using the Kipp apparatus.

Kipp apparatus

Hydrogen sulfide properties

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, then transparent condensation (water) will appear on its walls.

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

2H₂S + О₂ → 2Н₂О + 2S

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

When igniting a previously prepared gaseous mixture of hydrogen sulfide and oxygen, an explosion occurs.

The reaction of hydrogen sulfide and sulfur (IV) oxide also allows you to get free sulfur:

2H₂S + SО₂ → 2Н₂О + 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 hydrosulfuric acid (HS). This acid is also called hydrogen sulphide water. As you can see, the formulas of gas-hydrogen sulfide and hydrogen sulfide acid are written in the same way.

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

H₂S + Pb (NO₃) ₂ → PbS + 2HNO₃

This is a qualitative reaction for detecting hydrogen sulfide. It also demonstrates the ability of hydrogen sulfide 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, it almost completely decomposes into hydrogen and free sulfur:

H₂S → Н₂ + S

Hydrogen sulfide interacts intensively with aqueous solutions of halogens:

H₂S + 4Cl₂ + 4H₂O → H₂SO₄ + 8HCl

Hydrogen sulfide in nature and human life

Hydrogen sulfide is a 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 precipitation of heavy metal sulfides, which are usually insoluble);
• in organic synthesis (for the production of sulfur analogs of organic alcohols (mercaptans) and thiophene (a sulfur-containing aromatic hydrocarbon). Another of the recently emerging areas in science is hydrogen sulfide energy. Energy production from hydrogen sulfide deposits from the bottom of the Black Sea is seriously studied.

The nature of redox reactions of sulfur and hydrogen

The reaction of formation of hydrogen sulfide is redox:

Н₂⁰ + S⁰ → H₂⁺S²⁻

The process of interaction of sulfur with hydrogen is easily explained by the structure of their atoms. Hydrogen ranks first in periodic system, therefore, the charge of its atomic nucleus is equal to (+1), and 1 electron is circling 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:

Н⁰ -1е⁻ = Н⁺

Sulfur is at the sixteenth position 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 arrangement of sulfur in the third period suggests 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 (VI) oxide:

2S⁰ + 3O2⁰ → 2S⁺⁶O₃⁻²

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

S⁰ + О2⁰ → 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 oxidizes, 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 it is they who lose electrons, restoring the external energy level 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 chemical reaction the formation of hydrogen sulphide, sulfur acts as an oxidizing agent.

From the point of view of the manifestation of sulfur of various oxidation states, another interaction of sulfur (IV) oxide 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 (II) oxide molecule, 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 - oxidizing agent, 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 NU); t ° pl. = -86 ° C; bale t ° = -60 ° C.

The effect of hydrogen sulfide on the body:

Hydrogen sulfide not only smells bad, it is also extremely poisonous. When this gas is inhaled in large quantities, paralysis of the respiratory nerves quickly sets in, and then the person stops smelling - 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 where it is not so easy to get out quickly.

Receiving

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 - 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 stage)

Hydrogen sulfide 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 regenerative 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 differently:

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 items can be returned to their shine. To do this, in an enamel bowl, they are boiled with a solution of soda and aluminum foil... Aluminum reduces silver to metal, while soda solution retains sulfur ions.

6) Qualitative reaction for 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 ↓

Air 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 art paintings by old masters was the use of lead white, which, over several centuries, interacting with traces of hydrogen sulfide in the air (formed in small quantities during decay of proteins; in the atmosphere of industrial regions, etc.) turn into PbS. Lead white is a pigment that is lead carbonate ( II). It reacts with hydrogen sulfide in the polluted atmosphere to form lead sulfide ( II), black connection:

PbCO 3 + H 2 S = PbS↓ + CO 2 + H 2 O

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

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

in this case, lead sulfate is formed ( II), the compound is white.

In this way, blackened oil paintings are restored.

7) Restoration:

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

Sulphides

Sulfide production

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

Hg + S → HgS

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

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 standing 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 ANCHORING

Task number 1
Write down the reaction equations with which you can carry out the following transformations:
Cu→ CuS→ H 2 S→ SO 2

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

Task number 3
Write down the equation of the chemical reaction of hydrogen sulfide with a solution of lead (II) nitrate in molecular, full and short ionic form. Note 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 that precipitated as a result of this reaction.

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

Hydrogen sulfide (H 2 S) - very carcinogenic, toxic gas. Has a pungent characteristic smell of rotten eggs.

Obtaining 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 sulphide is more pure than with the first production method):

Al 2 S 3 + 6H 2 O = 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 absence of hydrogen bonds, the boiling point of H 2 S higher than oxygen. Same H 2 S poorly soluble in water, which also indicates the absence of hydrogen bonds).

H 2 S + Br 2 = 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 oxidants:

H 2 S + 4Cl 2 + 4H 2 O = 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 intermediate 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 precipitate.