Sulphate acid: formula and chemical properties

One of the very first mineral acids that has become known to man is sulfuric, or sulfate. Not only she herself, but also many of her salts were used in construction, medicine, food industry, for technical purposes. So far, nothing has changed in this respect. A number of characteristics that sulfate acid possesses make it simply irreplaceable in chemical syntheses. In addition, practically all branches of everyday life and industry find use of its salt. Therefore, we will consider in detail what it is and what the features of the manifested properties consist in.

Variety of names

To begin with, there are many names for this substance. Among them there are those that are formed according to the rational nomenclature, and those that are historically formed. So, this connection is denoted as:

• Sulfate acid;
• oil of vitriol;
• sulfuric acid;
• oleum.

Although the term "oleum" is not entirely suitable for this substance, since it is a mixture of sulfuric acid and higher sulfur oxide - SO ₃ .

Sulfatic acid: the formula and structure of a molecule

From the point of view of the chemical abbreviation, the formula for this acid can be written as follows: H ₂ SO ₄ . It is obvious that the molecule consists of two hydrogen cations and an anion of the acid residue - a sulfate ion having a charge of 2+.

At the same time, the following bonds act within the molecule:

• Covalent polar between sulfur and oxygen;
• Covalently strongly polar between hydrogen and the acid residue of SO ₄ .

Sulfur, having 6 unpaired electrons, forms two double bonds with two oxygen atoms. Another pair - single, and those in turn - single with hydrogen. As a result, the structure of the molecule allows it to be strong enough. At the same time, the hydrogen cation is very mobile and easily leaves, because sulfur and oxygen are much more electronegative. By pulling the electron density on themselves, they provide the hydrogen with a partially positive charge, which when fully disconnected becomes full. So acidic solutions are formed in which there is H ⁺ .

If we talk about the degree of oxidation of the elements in the compound, then the sulfate acid, whose formula H ₂ SO ₄ , makes it possible to calculate them: for hydrogen +1, for oxygen -2, for sulfur +6.

As in any molecule, the total charge is zero.

History of the discovery

Sulfatic acid is known to people since ancient times. Even the alchemists knew how to obtain it by methods of calcination of various vitriol. Since the IX century people have received and used this substance. Later in Europe, Albert Magnus learned how to extract acid in the process of decomposition of iron sulfate.

However, none of the ways was not profitable. Then came the so-called chamber version of synthesis. For this purpose, sulfur and nitrate were burned, and the evolved vapors were absorbed with water. As a result, sulfate acid was formed.

Even later, the British managed to find the cheapest method of obtaining this substance. For this, pyrite-FeS ₂ , iron pyrites was used. Its firing and subsequent interaction with oxygen still constitute one of the most important industrial methods for the synthesis of sulfuric acid. Such raw materials are more affordable, cheaper and of high quality for large volumes of production.

Physical properties

There are several parameters, including external ones, in which sulfate acid differs from others. Its physical properties can be described in several points:

1. Under standard conditions, liquid.
2. In the concentrated state it is heavy, oily, for which it was called "vitriolic oil".
3. The density of the substance is 1.84 g / cm ³ .
4. Does not have color and smell.
5. Has a pronounced "copper" taste.
6. It dissolves in water very well, almost unlimitedly.
7. Hygroscopic, able to capture both free and bound water from tissues.
8. Non-volatile.
9. The boiling point is 296 ° C.
10. Melting at 10.3 ° C.

One of the most important features of this compound is the ability to hydrate with the release of a large amount of heat. That is why even from the school's bench children are taught that it is impossible to add water to acid, but only vice versa. After all, the density of water is easier, so it will accumulate on the surface. If you sharply add it to the acid, then as a result of the dissolution reaction, so much energy will be released that the water will boil and start splashing together with the particles of the dangerous substance. This can cause severe chemical burns on the skin of the hands.

Therefore, it is necessary to pour acid into the water with a thin trickle, then the mixture will heat up strongly, but effervescence will not occur, which means that the liquid is sprayed too.

Chemical properties

From the point of view of chemistry, this acid is very strong, especially if it is a concentrated solution. It is dibasic, so it dissociates stepwise, forming a hydrogen sulfate and sulfate anion.

In general, its interaction with various compounds corresponds to all the basic reactions characteristic of this class of substances. It is possible to give examples of several equations in which sulfate acid takes part. Chemical properties are manifested in its interaction with:

• Salts;
• Oxides and hydroxides of metals;
• Amphoteric oxides and hydroxides;
• Metals standing in a series of stresses up to hydrogen.

As a result of such interactions, in almost all cases, the average salts of this acid (sulfates) or acid (hydrosulfates) are formed.

A special feature is also that only the solution of this substance, that is, dilute acid, reacts with metals in the usual Me + H ₂ SO ₄ = MeSO ₄ + H ₂ ↑ scheme. If you take concentrated or highly saturated (oleum), then the interaction products will be quite different.

Special properties of sulfuric acid

To such is the interaction of concentrated solutions with metals. So, there is a certain scheme that reflects the whole principle of such reactions:

1. If the metal is active, the result is the formation of hydrogen sulfide, salt and water. That is, sulfur is restored to -2.
2. If the metal is of medium activity, the result is sulfur, salt and water. That is, the reduction of the sulfate ion to free sulfur.
3. Metals of low chemical activity (after hydrogen) - sulfur dioxide, salt and water. Sulfur in oxidation state +4.

Also, special properties of sulfate acid are the ability to oxidize some non-metals to their highest oxidation state and react with complex compounds and oxidize them to simple substances.

Methods of production in industry

The sulfuric acid production process consists of two main types:

• contact;
• tower.

Both are the most common methods in the industry in all countries of the world. The first option is based on the use of iron pyrites or sulfur pyrite-FeS ₂ as a raw material. There are three stages in total:

1. Firing raw materials with the formation of sulphurous gas as a combustion product.
2. Transmission of this gas through oxygen over a vanadium catalyst to form sulfuric anhydride-SO ₃ .
3. In the absorption tower, anhydride is dissolved in a solution of sulfate acid with the formation of a solution of high concentration, oleum. Very heavy oily thick liquid.

The second option is practically the same, but nitrogen oxides are used as a catalyst. From the point of view of such parameters as product quality, cost and energy consumption, raw material purity, productivity, the first method is more efficient and acceptable, therefore, it is more often used.

Synthesis in the laboratory

If it is necessary to obtain sulfuric acid in small quantities for laboratory studies, then the best way is the way of interaction of hydrogen sulphide with sulfates of low-activity metals.

In these cases, black metal sulphides are formed, and sulfuric acid is formed as a by-product. For small studies, this option is suitable, but the purity of such an acid will not differ.

Also in the laboratory it is possible to conduct a qualitative reaction to sulfate solutions. The most common reagent is barium chloride, since the Ba ^{2+ ion,} together with the sulfate anion, precipitates in a white precipitate - barite milk: H ₂ SO ₄ + BaCL ₂ = 2HCL + BaSO ₄ ↓

The most common salts

Sulphate acid and sulfates, which it forms, are important compounds in many industries and households, including food. The most common salts of sulfuric acid are the following:

1. Gypsum (alabaster, selenite). The chemical name is aqueous calcium hydrate of calcium sulphate. Formula: CaSO ₄ . It is used in construction, medicine, pulp and paper industry, manufacturing of jewelry.
2. Barite (heavy spar). Sulphate of barium. In solution is a milk sediment. In solid form, transparent crystals. Used in optical instruments, X-rays, for the production of an insulating coating.
3. Mirabilite (Glauber's salt). The chemical name is sodium hydrated sodium sulfate. Formula: Na ₂ SO ₄ * 10H ₂ O. It is used in medicine as a laxative.

It is possible to cite as examples many salts that are of practical importance. However, the above are the most common.

Sulphated Lye

This substance is a solution that is formed due to the thermal treatment of wood, that is, cellulose. The main purpose of this compound is the preparation of sulfate soap on its basis by sedimentation. The chemical composition of sulfate liquor is as follows:

• Lignin;
• Hydroxy acids;
• Monosaccharides;
• Phenols;
• Resins;
• Volatile and fatty acids;
• Sulfides, chlorides, carbonates and sodium sulfates.

There are two main types of this substance: white and black sulphate liquor. White leaves for pulp and paper production, and black is used to produce sulphate soap in industry.

Main applications

The annual production of sulfuric acid is 160 million tons per year. This is a very significant figure, which indicates the importance and prevalence of this compound. There are several industries and places where it is necessary to use sulfate acid:

1. In the batteries as an electrolyte, especially in lead.
2. At factories where sulphate fertilizers are produced. The bulk of this acid goes exactly to the manufacture of mineral fertilizing for plants. Therefore, plants for the production of sulfuric acid and the production of fertilizers are most often built side by side.
3. In the food industry as an emulsifier, denoted by the code E513.
4. In numerous organic syntheses as a water-removing agent, a catalyst. Thus, explosives, resins, detergents, kapron, polypropylene and ethylene, dyes, chemical fibers, esters and other compounds are produced.
5. Used in filters for water purification and production of distilled water.
6. Applied in the extraction and processing of rare elements from ore.

Also, a lot of sulfuric acid goes to laboratory research, where it is obtained by local methods.