Sulfuric acid. Formula, properties, production and application

Sulfuric acid has a historical name: vitriolic oil. The study of acid began from ancient times, in its writings it was described: the Greek physician Dioscorides, the Roman naturalist Pliny the Elder, the Islamic alchemists Geber, Razi and Ibn Sina, others. In Sumer, there was a list of vitriol, which were classified by the color of the substance. In our time, the word "vitriol" combines crystalline hydrates of sulfates of divalent metals.

In the 17th century, the German-Dutch chemist Johann Glauber obtained sulfuric acid by burning sulfur with potassium nitrate (KNO3) in the presence of water vapor. In 1736, Joshua Ward (a pharmacist from London) used this method in production. This time can be considered a reference point, when sulfuric acid was already being produced on a large scale. Its formula (H2SO4), as it is commonly believed, was established by the Swedish chemist Berzelius (1779-1848), which later was mute.

Berzelius established with the help of letter symbols (designate chemical elements) and lower numerical indices (indicate the number of atoms in a given species) that one molecule contains 1 sulfur atom (S), 2 hydrogen atoms (H) and 4 oxygen atoms (O ). From this time, the qualitative and quantitative composition of the molecule became known, that is, sulfuric acid is described in the language of chemistry.

The structural formula, showing graphically the mutual arrangement of atoms and chemical bonds between them in the molecule (they are usually denoted by lines), informs that there is a sulfur atom in the center of the molecule, which is linked by double bonds to two oxygen atoms. With the other two oxygen atoms, to each of which a hydrogen atom is attached, the same sulfur atom is connected by single bonds.

Properties

Sulfuric acid is a slightly yellowish or colorless, viscous liquid soluble in water at any concentration. It is a strong mineral acid. Acid is highly aggressive towards metals (concentrated does not interact with iron without heating, and passivates it), rocks, animal tissues or other materials. Characterized by high hygroscopicity and pronounced properties of a strong oxidizer. At a temperature of 10.4 ° C, the acid solidifies. When heated to 300 оС, almost 99% acid loses sulfuric anhydride (SO3).

Its properties vary depending on the concentration of its aqueous solution. There are generally accepted names for acid solutions. Dilute acid is considered to be up to 10%. Rechargeable - from 29 to 32%. At a concentration of less than 75% (as specified in GOST 2184), it is called a tower. If the concentration is 98%, then it will already be concentrated sulfuric acid. Formula (Chemical or structural) in all cases remains unchanged.

When sulfuric acid is dissolved in concentrated sulfuric anhydride, oleum or fuming sulfuric acid is formed, its formula can be written as follows: H2S2O7. Pure acid (H2S2O7) is a solid with a melting point of 36 ° C. Hydration reactions of sulfuric acid are characterized by the release of heat in large quantities.

Diluted acid reacts with metals, reacting with which, exhibits the properties of a strong oxidizer. At the same time sulfuric acid is restored, the formula of the formed substances containing the reduced (up to +4, 0 or -2) sulfur atom, can be: SO2, S or H2S.

Reacts with non-metals, for example, carbon or sulfur:

2 H2SO4 + C → 2 SO2 + CO2 + 2 H2O

2 H2SO4 + S → 3 SO2 + 2 H2O

Reacts with sodium chloride:

H2SO4 + NaCl → NaHSO4 + HCl

It is characterized by the reaction of electrophilic substitution of a hydrogen atom attached to the benzene ring of an aromatic compound to the group -SO3H.

Receiving

In 1831, the contact method of obtaining H2SO4 was patented, which is now the main one. Today, most of the sulfuric acid is produced using this method. As raw materials, sulfide ore is used (more often iron pyrite, FeS2), which is fired in special furnaces, while calcining gas is formed. Since the gas temperature is 900 ° C, it is cooled with sulfuric acid at a concentration of 70%. Then, the gas in a cyclone and an electrostatic precipitator is cleaned of dust, in wash towers with acid at a concentration of 40 and 10% of the catalytic poisons (As2O5 and fluorine), on wet electrostatic precipitators from the acid aerosol. Next, a calcined gas containing 9% sulfur dioxide (SO2) is dried and fed to a contact apparatus. Passing through 3 layers of the vanadium catalyst, SO2 is oxidized to SO3. To dissolve the sulfuric anhydride formed, concentrated sulfuric acid is used. The formula for the solution of sulfuric anhydride (SO3) in anhydrous sulfuric acid is H2S2O7. In this form, the oleum in steel tanks is transported to the consumer, where it is diluted to the desired concentration.

Application

Due to its different chemical properties, H2SO4 has a wide range of applications. In the production of acid itself, as an electrolyte in lead-acid batteries, for the manufacture of various cleaning agents, is also an important reagent in the chemical industry. It is also used in the production of: alcohols, plastics, dyes, rubber, ether, adhesives, explosives, soaps and detergents, pharmaceuticals, cellulose and paper, petroleum products.