Sulfur oxide exhibits acidic properties when reacting with. Sulfur - chemical properties, production, compounds
Sulfur oxide (IV) has acidic properties, which are manifested in reactions with substances that exhibit basic properties. Acidic properties are manifested when interacting with water. This produces a sulfuric acid solution:
The oxidation state of sulfur in sulfur dioxide (+4) determines the reducing and oxidizing properties of sulfur dioxide:
These enzymes may not be completely inactivated during juice processing because the high cellulose content generally found in tropical fruit juices makes it difficult to thermally inactivate these enzymes. The addition of sulfite prevents the breakdown of ascorbic acid during product processing and storage, avoiding oxidation caused by the enzymes ascorbic acid oxidase 13.
Non-enzymatic browning control. Fruit juices have specific color, flavor and aroma characteristics. These characteristics, as a rule, undergo modification during their processing and storage, which leads to a general degradation of the product. The three most important non-enzymatic darkening mechanisms in fruit juices are: 1 - the Maillard reaction, which occurs between reducing sugars and γ-amino groups of amino acids, peptides and proteins, resulting in the formation of melanoidins; 2 - oxidation of ascorbic acid to furfural and alpha-ketogulonic acid, which form dark brown pigments in the presence of nitrogen compounds; in addition to generating a simple polymerization formed furfur light brown pigments; 3 - caramelization of sugars, which occurs under the action of acids on sugars, which leads to the formation of hydroxymethylfurfural, which polymerizes the formation of melanoidins, brown pigments 47.
vo-tel: S + 4 - 2e => S + 6
oct: S+4 + 4e => S0
Reducing properties are manifested in reactions with strong oxidizing agents: oxygen, halogens, nitric acid, potassium permanganate and others. For example:
2SO2 + O2 = 2SO3
S+4 - 2e => S+6 2
O20 + 4e => 2O-2 1
With strong reducing agents, the gas exhibits oxidizing properties. For example, if you mix sulfur dioxide and hydrogen sulfide, they interact under normal conditions:
Non-enzymatic darkening reactions lead to destruction nutrients, such as essential amino acids and ascorbic acid, reduces the digestibility of proteins, inhibits the action of digestive enzymes and interferes with the absorption of minerals, promoting the complexation of metal ions. Potentially toxic mutagenic products may be formed due to the Maillard reaction 19.
Generally, non-enzymatic browning can be inhibited or controlled in a variety of ways using low temperatures storage by removing oxygen from the packaging and using chemical inhibitors such as sulfites 47. Sulfur dioxide is probably the most effective non-enzymatic roasting in food 10.
2H2S + SO2 = 3S + 2H2O
S-2 - 2e => S0 2
S+4 + 4e => S0 1
Sulfurous acid exists only in solution. It is unstable and decomposes into sulfur dioxide and water. Sulfurous acid is not a strong acid. It is an acid of medium strength and dissociates in steps. When alkali is added to sulfuric acid, salts are formed. Sulfurous acid gives two series of salts: medium - sulfites and acidic - hydrosulfites.
The chemical mechanism by which sulfur dioxide inhibits non-enzymatic browning is not fully understood and is believed to be the reaction of bisulfite with the active carbonyl groups of sugar molecules and vitamin C10. Sulfite interacts with various components present in foods, including: reducing sugars, aldehydes , ketones, proteins and anthocyanins 53, while sulfite in its bound form is reduced in acidic foods. The degree of reaction depends on pH, temperature, sulfite concentration and reactive components present in the product.
Sulfur(VI) oxide
Sulfur trioxide exhibits acidic properties. It reacts violently with water and releases a large number of warmth. This reaction is used to make essential product chemical industry - sulfuric acid.
SO3 + H2O = H2SO4
Since the sulfur in sulfur trioxide has the highest degree oxidation, then sulfur(VI) oxide exhibits oxidizing properties. For example, it oxidizes halides, non-metals with low electronegativity:
One of the principles governing the use of food additives is their safety, however it is not possible to determine absolute proof of their toxicity to all people. Toxicological tests refer to physiological effects in experimental animals in relation to a certain ingestion ratio.
This group concluded that sulfites are not teratogenic, mutagenic, or carcinogenic in laboratory animals. They also found no significant toxicological or metabolic data.54 Sulfites used to be popular with restaurant owners for use in salads because they contained fresh fresh fruits and vegetables, but their use was banned after some people developed dangerous allergic reactions. Consequently, in many products, only a small proportion of the added sulfite remains in free form in final product 18.
2SO3 + C = 2SO2 + CO2
S+6 + 2e => S+4 2
C0 - 4e => C+4 2
Sulfuric acid enters into reactions of three types: acid-base, ion-exchange, redox. It also actively interacts with organic substances.
Acid-base reactions
Sulfuric acid exhibits acidic properties in reactions with bases and basic oxides. These reactions are best carried out with dilute sulfuric acid. Since sulfuric acid is dibasic, it can form both medium salts (sulfates) and acidic salts (hydrosulfates).
The biotransformation of sulfite consists of its oxidation to sulfate by the action of the sulfite oxidase enzyme located in the mitochondria present in tissues, mainly the heart, liver and kidneys. In the human body, this enzyme also converts from sulfur amino acids to sulfites. This normal metabolic process controls the excess of these amino acids by oxidizing them to sulfates that are easily eliminated. In all species studied, most of the sulfite consumed is rapidly excreted as sulfate, which can interact with proteins to form a protein-thiosulfonate complex that can be stored in the body.
Ion exchange reactions
Sulfuric acid is characterized by ion exchange reactions. At the same time, it interacts with salt solutions, forming a precipitate, a weak acid, or releasing a gas. These reactions are carried out at a faster rate if you take 45% or even more dilute sulfuric acid. Gas evolution occurs in reactions with salts of unstable acids, which decompose to form gases (carbonic, sulfurous, hydrogen sulfide) or to form volatile acids, such as hydrochloric.
Asthma and sulfite oxidase deficient people tolerate up to a certain amount of sulfite without being sensitive. There is another non-specific enzyme that also oxidizes sulfite to sulfate, xanthine oxidase 21. According to Taylor 19, the only adverse effect associated with sulfite sensitivity is asthma, although only a small percentage of asthmatics are sulfite sensitive.
A food additive is any additive intentionally added to food, without a nutritional purpose, for the purpose of altering the physical, chemical, biological or sensory characteristics in the production, processing, preparation, handling, packaging, storage, transport or processing of food 59. However the concept of a nutritional supplement varies widely from country to country. An individual substance may be used as an additive in one country and banned in another 60.
Redox reactions
Sulfuric acid most clearly manifests its properties in redox reactions, since sulfur in its composition has the highest oxidation state of +6. The oxidizing properties of sulfuric acid can be found in the reaction, for example, with copper.
There are two oxidizing elements in the sulfuric acid molecule: a sulfur atom with S.O. +6 and hydrogen ions H+. Copper cannot be oxidized by hydrogen to the +1 oxidation state, but sulfur can. This is the reason for the oxidation of such an inactive metal as copper with sulfuric acid.
In Brazil, additives are classified into 23 functional classes, among which are preservatives, which are defined as substances that prevent or delay the alteration of foodstuffs caused by microorganisms or enzymes. Sulfur dioxide and its derivatives are classified as conservative 59.
However, in the specific case of cashew juice, it is necessary to use more high levels sulfur dioxide than for other fruit juices, in order to avoid browning and loss of flavor, flavor and nutritional value characteristics. Preservation of tropical fruit juices by adding sulfur dioxide followed by heat treatment is the method most used in the processing industries, as this additive has proven effective in controlling microorganisms and enzymatic and non-enzymatic toasting, which greatly contributed to maintaining the quality of processed juices for a longer period. time.
In dilute solutions of sulfuric acid, the oxidizing agent is predominantly the hydrogen ion H+. In concentrated solutions, especially in hot ones, the oxidizing properties of sulfur in the +6 oxidation state predominate.
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Several allotropic modifications sulfur - rhombic, monoclinic, plastic sulfur. The most stable modification is rhombic sulfur, all other modifications spontaneously turn into it after a while.
In addition, this additive is considered toxicologically safe, provided that it does not exceed the limits allowed by Brazilian law. Beverage winners: the use of amino acids and peptides in sports nutrition. Functional products: Japanese approach.
Modern nutrition in the field of health and disease. 8th ed. Tropical Fruit Processing Association. Fruit juice export report. Brazilian Agriculture Yearbook. Sulfite food additives: to ban or not? Review of sulfites in foods: analytical methodology and published results.
Sulfur can donate its electrons when interacting with stronger oxidizing agents:
In these reactions, sulfur is the reducing agent.
It should be emphasized that sulfur oxide (VI) can be formed only in the presence of or and high pressure (see below).
When interacting with metals, sulfur exhibits oxidizing properties:
Microbiology of juices, cellulose and acid products. The interaction of food additives and additives involving sulfur dioxide, ascorbic and nitrous acids - a review. Antimicrobial food additives: Characteristics use effects. 2nd ed. Browning products: control of sulfites, antioxidants and other means.
Chemical preservation of food. Factors influencing the death of yeast by sulfur dioxide. Chemical preservatives in food. Food chemistry: mechanisms and theory. Food additives in the toxicological aspect. 2nd ed. Disinfection, sterilization and conservation.
Sulfur reacts with most metals when heated, but in the reaction with mercury, the interaction occurs already at room temperature.
This circumstance is used in laboratories to remove spilled mercury, the vapors of which are a strong poison.
Sodium benzoate and benzoic acid. New York: Marcel Decker; with. 11. Conservative benzoic acid and sorbic acid. Present and future use of traditional antimicrobials. Bromatological and toxicological aspects of benzoic and sorbic preservatives.
Enzymes and pigments: influence and changes during processing. A guide to fruit industrialization. Biochemistry of tropical fruits. Some technological aspects of tropical fruits and their products. Behavior of polyphenol oxidases in foods. Phenolic compounds and polyphenol oxidase in relation to toasting in grapes and wines.
Hydrogen sulfide, hydrosulfide acid, sulfides.
When sulfur is heated with hydrogen, a reversible reaction occurs
with a very low yield of hydrogen sulfide. Usually obtained by the action of dilute acids on sulfides:
Hydrogen sulfide is a colorless gas with the smell of rotten eggs, poisonous. One volume of water under normal conditions dissolves 3 volumes of hydrogen sulfide.
Physical and chemical methods used to control the enzymatic browning of vegetables. Enzymatic toasting reactions in apple and apple products. Polyphenol oxidase and peroxidase in fruits and vegetables. Mechanism of sulfite inhibition of browning caused by polyphenol oxidase.
Effect of sulfur dioxide on oxidizing enzyme systems in plant tissues. Polyphenol oxidase in plants. Kinetic study irreversible inhibition enzyme inhibitor, which is unstable due to enzymatic catalysis. Biochemistry of fruits and their influence on processing. Fruit processing: nutrition, products and quality management. 2nd ed.
Hydrogen sulfide is a typical reducing agent. It burns in oxygen (see above). A solution of hydrogen sulfide in water is a very weak hydrosulfide acid, which dissociates in steps and mainly in the first stage:
Hydrosulfuric acid, like hydrogen sulfide, is a typical reducing agent.
Sanitary control of food products. 2nd ed. Preservatives: Alternative Methods for Fighting Bacteria. Toxic agents enter directly into food. Sao Paulo: Varela; R. 61. Food chemistry: theory and practice. 1st ed. Federation of American Societies for Experimental Biology.
Food safety and food technology. Nutrition: concepts and controversies. 8th ed. Food labeling: declaration of sulphurizing agents. Assessment of sulfur dioxide content and microbiological quality of canned mushrooms. Chemistry of sulfonating agents in food.
Hydrosulfuric acid is oxidized not only by strong oxidizing agents, such as chlorine,
but also weaker ones, such as sulfurous acid
or ferric ions:
Hydrosulfide acid can react with bases, basic oxides or salts, forming two series of salts: medium - sulfides, acidic - hydrosulfides.
Decree No. 540 of the Ministry of Health. Approves Technical regulation: Food additives - definitions, classification and employment. Legislation of food additives. Resolution No. 04 National Council healthcare. Resolution 12 of the National Sanitary Inspection Agency.
Also, the Persian alchemist Al-Razi is credited with the first descriptions of this substance. Further improvements to this process by the French chemist Gay-Lussac and the British chemist John Glover improved the concentration of the resulting acid. The history of sulfuric acid is discussed in more detail in our article.
Most sulfides (with the exception of sulfides of alkali and alkaline earth metals, as well as ammonium sulfide) are poorly soluble in water. Sulfides, as salts of a very weak acid, undergo hydrolysis.
Sulfur oxide (IV). Sulfuric acid.
SO2 is formed when sulfur is burned in oxygen or when sulfides are burned; it is a colorless gas with a pungent odor, highly soluble in water (40 volumes in 1 volume of water at 20 °C).
Geology, climatology and astrophysics
History of obtaining the most useful chemical substances. Sulfuric acid is formed naturally due to emissions from volcanoes that produce sulfur dioxide, which oxidizes into the atmosphere and then reacts with air humidity. It also forms in bubbles in water bodies near volcanic activity and lakes formed inside volcanic craters.
It is also formed along with hydrogen chloride and hence hydrochloric acid when volcanic lava comes into contact with seawater. Vapor clouds containing sulfuric acid. These hydrates are likely to occur in the Earth's stratosphere and may provide sites for high-altitude ice clouds to condense, which can significantly affect the Earth's climate, especially after volcanic eruptions when large amounts of sulfur are deposited in the atmosphere above. In particular, the area pure ice sulfuric acid hemihexachar, including detailed studies of sulfuric acid octahydrate.
Sulfur oxide (IV) is anhydride of sulfurous acid, therefore, when dissolved in water, a reaction with water partially occurs and weak sulfurous acid is formed:
which is unstable, easily breaks up again into. In an aqueous solution of sulfur dioxide, the following equilibria simultaneously exist.
Sulfur oxide (IV) has acidic properties, which are manifested in reactions with substances that exhibit basic properties. Acidic properties are manifested when interacting with water. In this case, a solution of sulfuric acid is formed:
The oxidation state of sulfur in sulfur dioxide (+4) determines the reducing and oxidizing properties of sulfur dioxide:
vo-tel: S + 4 - 2e => S + 6
oct: S+4 + 4e => S0
Reducing properties are manifested in reactions with strong oxidizing agents: oxygen, halogens, nitric acid, potassium permanganate and others. For example:
2SO2 + O2 = 2SO3
S+4 - 2e => S+6 2
O20 + 4e => 2O-2 1
With strong reducing agents, the gas exhibits oxidizing properties. For example, if you mix sulfur dioxide and hydrogen sulfide, they interact under normal conditions:
2H2S + SO2 = 3S + 2H2O
S-2 - 2e => S0 2
S+4 + 4e => S0 1
Sulfurous acid exists only in solution. It is unstable and decomposes into sulfur dioxide and water. Sulfurous acid is not a strong acid. It is an acid of medium strength and dissociates in steps. When alkali is added to sulfuric acid, salts are formed. Sulfurous acid gives two series of salts: medium - sulfites and acidic - hydrosulfites.
Sulfur(VI) oxide
Sulfur trioxide exhibits acidic properties. It reacts violently with water, and a large amount of heat is released. This reaction is used to obtain the most important product of the chemical industry - sulfuric acid.
SO3 + H2O = H2SO4
Since sulfur in sulfur trioxide has the highest oxidation state, sulfur(VI) oxide exhibits oxidizing properties. For example, it oxidizes halides, non-metals with low electronegativity:
2SO3 + C = 2SO2 + CO2
S+6 + 2e => S+4 2
C0 - 4e => C+4 2
Sulfuric acid enters into reactions of three types: acid-base, ion-exchange, redox. It also actively interacts with organic substances.
Acid-base reactions
Sulfuric acid exhibits acidic properties in reactions with bases and basic oxides. These reactions are best carried out with dilute sulfuric acid. Since sulfuric acid is dibasic, it can form both medium salts (sulfates) and acidic salts (hydrosulfates).
Ion exchange reactions
Sulfuric acid is characterized by ion exchange reactions. At the same time, it interacts with salt solutions, forming a precipitate, a weak acid, or releasing a gas. These reactions proceed at a faster rate when using 45% or even more dilute sulfuric acid. Gas evolution occurs in reactions with salts of unstable acids, which decompose to form gases (carbonic, sulfurous, hydrogen sulfide) or to form volatile acids, such as hydrochloric.
Redox reactions
Sulfuric acid most clearly manifests its properties in redox reactions, since sulfur in its composition has the highest oxidation state of +6. The oxidizing properties of sulfuric acid can be found in the reaction, for example, with copper.
There are two oxidizing elements in the sulfuric acid molecule: a sulfur atom with S.O. +6 and hydrogen ions H+. Copper cannot be oxidized by hydrogen to the +1 oxidation state, but sulfur can. This is the reason for the oxidation of such an inactive metal as copper with sulfuric acid.
Sulfur is located in group VIa Periodic system chemical elements DI. Mendeleev.
On the outside energy level sulfur contains 6 electrons, which have 3s 2 3p 4 . In compounds with metals and hydrogen, sulfur exhibits a negative oxidation state of elements -2, in compounds with oxygen and other active non-metals - positive +2, +4, +6. Sulfur is a typical non-metal, depending on the type of transformation, it can be an oxidizing agent and a reducing agent.
Finding sulfur in nature
Sulfur occurs in the free (native) state and bound form.
The most important natural sulfur compounds:
FeS 2 - iron pyrite or pyrite,
ZnS - zinc blende or sphalerite (wurtzite),
PbS - lead gloss or galena,
HgS - cinnabar,
Sb 2 S 3 - antimonite.
In addition, sulfur is present in oil, natural coal, natural gases, natural waters(in the form of a sulfate ion and causes a "permanent" hardness fresh water). Vital element for higher organisms, component many proteins, concentrated in the hair.
Allotropic modifications of sulfur
Allotropy- this is the ability of the same element to exist in different molecular forms (molecules contain different amount atoms of the same element, for example, O 2 and O 3, S 2 and S 8, P 2 and P 4, etc.). 
Sulfur is distinguished by its ability to form stable chains and cycles of atoms. The most stable are S 8 , which form rhombic and monoclinic sulfur. This is crystalline sulfur - a brittle yellow substance.
Open chains have plastic sulfur, a substance Brown, which is obtained by sharp cooling of the sulfur melt (plastic sulfur becomes brittle after a few hours, turns yellow and gradually turns into rhombic). 
1) rhombic - S 8
t°pl. = 113°C; r \u003d 2.07 g / cm 3
The most stable version.
2) monoclinic - dark yellow needles
t°pl. = 119°C; r \u003d 1.96 g / cm 3
Stable at temperatures over 96°C; under normal conditions, it turns into a rhombic one.
3) plastic - brown rubbery (amorphous) mass
Unstable, when hardened, turns into a rhombic
Sulfur recovery
- The industrial method is the smelting of ore with the help of steam.
- Incomplete oxidation of hydrogen sulfide (with a lack of oxygen):
2H 2 S + O 2 → 2S + 2H 2 O
- Wackenroder reaction:
2H 2 S + SO 2 → 3S + 2H 2 O
Chemical properties of sulfur
Oxidizing properties of sulfur
(S 0
+ 2ē→ S -2
)
1) Sulfur reacts with alkaline without heating:
S + O 2 – t° → S +4 O 2
2S + 3O 2 - t °; pt → 2S +6 O 3
4) (except for iodine):
S + Cl2 → S +2 Cl 2
S+3F2 → SF6
With complex substances:
5) with acids - oxidizing agents:
S + 2H 2 SO 4 (conc) → 3S +4 O 2 + 2H 2 O
S + 6HNO 3 (conc) → H 2 S +6 O 4 + 6NO 2 + 2H 2 O
Disproportionation reactions:
6) 3S 0 + 6KOH → K 2 S +4 O 3 + 2K 2 S -2 + 3H 2 O
7) sulfur dissolves in a concentrated solution of sodium sulfite:
S 0 + Na 2 S +4 O 3 → Na 2 S 2 O 3 sodium thiosulfate
The +4 oxidation state for sulfur is quite stable and manifests itself in SHal 4 tetrahalides, SOHal 2 oxodihalides, SO 2 dioxide, and their corresponding anions. We will get acquainted with the properties of sulfur dioxide and sulfurous acid.
1.11.1. Sulfur oxide (IV) The structure of the so2 molecule
The structure of the SO 2 molecule is similar to the structure of the ozone molecule. The sulfur atom is in a state of sp 2 hybridization, the shape of the orbitals is a regular triangle, the shape of the molecule is angular. The sulfur atom has an unshared electron pair. The S-O bond length is 0.143 nm, the bond angle is 119.5°.
The structure corresponds to the following resonant structures:
Unlike ozone, the S–O bond multiplicity is 2, i.e., the first resonance structure makes the main contribution. The molecule is characterized by high thermal stability.
Physical properties
Under normal conditions, sulfur dioxide or sulfur dioxide is a colorless gas with a pungent suffocating odor, melting point -75 °C, boiling point -10 °C. Let's well dissolve in water, at 20 °C in 1 volume of water 40 volumes of sulfur dioxide are dissolved. Toxic gas.
Chemical properties of sulfur oxide (IV)
Sulfur dioxide is highly reactive. Sulfur dioxide is an acid oxide. It is quite soluble in water with the formation of hydrates. It also partially interacts with water, forming a weak sulfurous acid, which is not isolated individually:
SO 2 + H 2 O \u003d H 2 SO 3 \u003d H + + HSO 3 - \u003d 2H + + SO 3 2-.
As a result of dissociation, protons are formed, so the solution has an acidic environment.
When sulfur dioxide gas is passed through a sodium hydroxide solution, sodium sulfite is formed. Sodium sulfite reacts with excess sulfur dioxide to form sodium hydrosulfite:
2NaOH + SO 2 = Na 2 SO 3 + H 2 O;
Na 2 SO 3 + SO 2 \u003d 2NaHSO 3.
Sulfur dioxide is characterized by redox duality, for example, it, showing reducing properties, discolors bromine water:
SO 2 + Br 2 + 2H 2 O \u003d H 2 SO 4 + 2HBr
and potassium permanganate solution:
5SO 2 + 2KMnO 4 + 2H 2 O \u003d 2KНSO 4 + 2MnSO 4 + H 2 SO 4.
oxidized by oxygen to sulfuric anhydride:
2SO 2 + O 2 \u003d 2SO 3.
It exhibits oxidizing properties when interacting with strong reducing agents, for example:
SO 2 + 2CO \u003d S + 2CO 2 (at 500 ° C, in the presence of Al 2 O 3);
SO 2 + 2H 2 \u003d S + 2H 2 O.
Production of sulfur oxide (IV)
Burning sulfur in air
S + O 2 \u003d SO 2.
Sulfide oxidation
4FeS 2 + 11O 2 \u003d 2Fe 2 O 3 + 8SO 2.
The action of strong acids on metal sulfites
Na 2 SO 3 + 2H 2 SO 4 \u003d 2NaHSO 4 + H 2 O + SO 2.
1.11.2. Sulfuric acid and its salts
When sulfur dioxide is dissolved in water, weak sulfurous acid is formed, the bulk of the dissolved SO 2 is in the form of a hydrated form of SO 2 H 2 O, upon cooling, a crystalline hydrate is also released, only a small part of the sulfurous acid molecules dissociates into sulfite and hydrosulfite ions. In the free state, the acid is not isolated.
Being dibasic, it forms two types of salts: medium - sulfites and acidic - hydrosulfites. Only alkali metal sulfites and hydrosulfites of alkali and alkaline earth metals dissolve in water.
In redox processes, sulfur dioxide can be both an oxidizing agent and a reducing agent because the atom in this compound has an intermediate oxidation state of +4.
How does the oxidizing agent SO 2 react with stronger reducing agents, for example with:
SO 2 + 2H 2 S \u003d 3S ↓ + 2H 2 O
How does the reducing agent SO 2 react with stronger oxidizing agents, for example with in the presence of a catalyst, with, etc.:
2SO 2 + O 2 \u003d 2SO 3
SO 2 + Cl 2 + 2H 2 O \u003d H 2 SO 3 + 2HCl
Receipt
1) Sulfur dioxide is formed during the combustion of sulfur:
2) In industry, it is obtained by firing pyrite:
3) In the laboratory, sulfur dioxide can be obtained:
Cu + 2H 2 SO 4 \u003d CuSO 4 + SO 2 + 2H 2 O
Application
Sulfur dioxide is widely used in the textile industry for bleaching various products. Moreover, it is used in agriculture for the destruction of harmful microorganisms in greenhouses and cellars. AT large quantities SO 2 is used to produce sulfuric acid.
Sulfur oxide (VI) – SO 3 (sulfuric anhydride)
Sulfuric anhydride SO 3 is a colorless liquid, which at temperatures below 17 ° C turns into a white crystalline mass. It absorbs moisture very well (hygroscopic).
Chemical properties
Acid-base properties
How a typical acid oxide sulfuric anhydride interacts:
SO 3 + CaO = CaSO 4
c) with water:
SO 3 + H 2 O \u003d H 2 SO 4
A special property of SO 3 is its ability to dissolve well in sulfuric acid. A solution of SO 3 in sulfuric acid is called oleum.
Oleum formation: H 2 SO 4 + n SO 3 \u003d H 2 SO 4 ∙ n SO 3
redox properties
Sulfur oxide (VI) is characterized by strong oxidizing properties (usually reduced to SO 2):
3SO 3 + H 2 S \u003d 4SO 2 + H 2 O
Getting and using
Sulfuric anhydride is formed during the oxidation of sulfur dioxide:
2SO 2 + O 2 \u003d 2SO 3
Pure sulfuric anhydride practical value does not have. It is obtained as an intermediate in the production of sulfuric acid.
H2SO4
Mention of sulfuric acid is first found among Arab and European alchemists. It was obtained by calcining iron sulfate (FeSO 4 ∙ 7H 2 O) in air: 2FeSO 4 \u003d Fe 2 O 3 + SO 3 + SO 2 or a mixture with: 6KNO 3 + 5S \u003d 3K 2 SO 4 + 2SO 3 + 3N 2, and the emitted vapors of sulfuric anhydride were condensed. Absorbing moisture, they turned into oleum. Depending on the method of preparation, H 2 SO 4 was called vitriol oil or sulfur oil. In 1595, the alchemist Andreas Libavius established the identity of both substances.
For a long time, vitriol oil was not widely used. Interest in it greatly increased after the 18th century. Indigo carmine, a stable blue dye, was discovered. The first factory for the production of sulfuric acid was founded near London in 1736. The process was carried out in lead chambers, at the bottom of which water was poured. A molten mixture of saltpeter with sulfur was burned in the upper part of the chamber, then air was let in there. The procedure was repeated until an acid of the required concentration was formed at the bottom of the container.
In the 19th century the method was improved: instead of saltpeter, nitric acid was used (it gives when decomposed in the chamber). To return nitrous gases to the system, special towers were designed, which gave the name to the whole process - the tower process. Factories operating according to the tower method still exist today.
Sulfuric acid is a heavy oily liquid, colorless and odorless, hygroscopic; dissolves well in water. When concentrated sulfuric acid is dissolved in water, a large amount of heat is released, so it must be carefully poured into water (and not vice versa!) And mix the solution.
A solution of sulfuric acid in water with an H2SO4 content of less than 70% is usually called dilute sulfuric acid, and a solution of more than 70% is called concentrated sulfuric acid.
Chemical properties
Acid-base properties
Dilute sulfuric acid exhibits all the characteristic properties of strong acids. She reacts:
H 2 SO 4 + NaOH \u003d Na 2 SO 4 + 2H 2 O
H 2 SO 4 + BaCl 2 \u003d BaSO 4 ↓ + 2HCl
The process of interaction of Ba 2+ ions with sulfate ions SO 4 2+ leads to the formation of a white insoluble precipitate BaSO 4 . This is qualitative reaction to sulfate ion.
Redox properties
In dilute H 2 SO 4 , H + ions are oxidizing agents, and in concentrated H 2 SO 4 sulfate ions are SO 4 2+ . SO 4 2+ ions are stronger oxidizing agents than H + ions (see diagram). 
AT dilute sulfuric acid dissolve metals that are in the electrochemical series of voltages to hydrogen. In this case, metal sulfates are formed and released:
Zn + H 2 SO 4 \u003d ZnSO 4 + H 2
Metals that are in the electrochemical series of voltages after hydrogen do not react with dilute sulfuric acid:
Cu + H 2 SO 4 ≠
concentrated sulfuric acid is a strong oxidizing agent, especially when heated. It oxidizes many, and some organic substances.
When concentrated sulfuric acid interacts with metals that are in the electrochemical series of voltages after hydrogen (Cu, Ag, Hg), metal sulfates are formed, as well as the product of sulfuric acid reduction - SO 2.
Reaction of sulfuric acid with zinc With more active metals (Zn, Al, Mg), concentrated sulfuric acid can be reduced to free. For example, when sulfuric acid interacts with, depending on the concentration of the acid, various products of sulfuric acid reduction can simultaneously form - SO 2, S, H 2 S:
Zn + 2H 2 SO 4 \u003d ZnSO 4 + SO 2 + 2H 2 O
3Zn + 4H 2 SO 4 = 3ZnSO 4 + S↓ + 4H 2 O
4Zn + 5H 2 SO 4 = 4ZnSO 4 + H 2 S + 4H 2 O
In the cold, concentrated sulfuric acid passivates some metals, for example, and therefore it is transported in iron tanks:
Fe + H 2 SO 4 ≠
Concentrated sulfuric acid oxidizes some non-metals (, etc.), recovering to sulfur oxide (IV) SO 2:
S + 2H 2 SO 4 \u003d 3SO 2 + 2H 2 O
C + 2H 2 SO 4 \u003d 2SO 2 + CO 2 + 2H 2 O
Getting and using
In industry, sulfuric acid is obtained by contact. The acquisition process takes place in three stages:
- Obtaining SO 2 by roasting pyrite:
4FeS 2 + 11O 2 = 2Fe 2 O 3 + 8SO 2
- Oxidation of SO 2 to SO 3 in the presence of a catalyst - vanadium (V) oxide:
2SO 2 + O 2 \u003d 2SO 3
- Dissolution of SO 3 in sulfuric acid:
H2SO4+ n SO 3 \u003d H 2 SO 4 ∙ n SO 3
The resulting oleum is transported in iron tanks. Sulfuric acid of the required concentration is obtained from oleum by pouring it into water. This can be expressed in a diagram:
H 2 SO 4 ∙ n SO 3 + H 2 O \u003d H 2 SO 4
Sulfuric acid finds a variety of uses in the most various areas National economy. It is used for drying gases, in the production of other acids, for the production of fertilizers, various dyes and medicines.
Salts of sulfuric acid
Most sulfates are highly soluble in water (slightly soluble CaSO 4 , even less PbSO 4 and practically insoluble BaSO 4). Some sulfates containing water of crystallization are called vitriol:
CuSO 4 ∙ 5H 2 O copper sulfate
FeSO 4 ∙ 7H 2 O ferrous sulfate
Salts of sulfuric acid have everything. Their relation to heating is special.
sulfates active metals( , ) do not decompose even at 1000 ° C, while others (Cu, Al, Fe) - decompose upon slight heating into metal oxide and SO 3:
CuSO 4 \u003d CuO + SO 3
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