Acids preparation and properties. Names of some inorganic acids and salts

Let's look at the most common ones in educational literature acid formulas:

It is easy to notice that all acid formulas have in common the presence of hydrogen atoms (H), which comes first in the formula.

Determination of the valence of an acid residue

From the above list it can be seen that the number of these atoms may differ. Acids that contain only one hydrogen atom are called monobasic (nitric, hydrochloric, and others). Sulfuric, carbonic, and silicic acids are dibasic, since their formulas contain two H atoms. A tribasic phosphoric acid molecule contains three hydrogen atoms.

Thus, the amount of H in the formula characterizes the basicity of the acid.

The atom or group of atoms that are written after hydrogen are called acid residues. For example, in hydrosulfide acid the residue consists of one atom - S, and in phosphoric, sulfurous and many others - of two, and one of them is necessarily oxygen (O). On this basis, all acids are divided into oxygen-containing and oxygen-free.

Each acid residue has a certain valency. It is equal to the number of H atoms in the molecule of this acid. The valence of the HCl residue is equal to one, since it is a monobasic acid. Residues of nitric, perchloric, and nitrous acids have the same valency. The valence of the sulfuric acid residue (SO 4) is two, since there are two hydrogen atoms in its formula. Trivalent phosphoric acid residue.

Acidic residues - anions

In addition to valence, acid residues have charges and are anions. Their charges are indicated in the solubility table: CO 3 2−, S 2−, Cl− and so on. Please note: the charge of the acid residue is numerically the same as its valency. For example, in silicic acid, the formula of which is H 2 SiO 3, the acid residue SiO 3 has a valence of II and a charge of 2-. Thus, knowing the charge of the acid residue, it is easy to determine its valence and vice versa.

Summarize. Acids are compounds formed by hydrogen atoms and acidic residues. From the point of view of the theory of electrolytic dissociation, another definition can be given: acids are electrolytes, in solutions and melts of which hydrogen cations and anions of acid residues are present.

Hints

Chemical formulas of acids are usually learned by heart, as are their names. If you have forgotten how many hydrogen atoms are in a particular formula, but you know what its acidic residue looks like, the solubility table will come to your aid. The charge of the residue coincides in modulus with the valence, and that with the amount of H. For example, you remember that the remainder of carbonic acid is CO 3 . Using the solubility table, you determine that its charge is 2-, which means it is divalent, that is, carbonic acid has the formula H 2 CO 3.

There is often confusion with the formulas of sulfuric and sulfurous, as well as nitric and nitrous acids. Here, too, there is one point that makes it easier to remember: the name of the acid from the pair in which there are more oxygen atoms ends in -naya (sulfuric, nitric). An acid with fewer oxygen atoms in the formula has a name ending in -istaya (sulphurous, nitrous).

However, these tips will only help if the acid formulas are familiar to you. Let's repeat them again.

These are substances that dissociate in solutions to form hydrogen ions.

Acids are classified by their strength, by their basicity, and by the presence or absence of oxygen in the acid.

By strengthacids are divided into strong and weak. The most important strong acids are nitric HNO 3, sulfuric H2SO4, and hydrochloric HCl.

According to the presence of oxygen distinguish between oxygen-containing acids ( HNO3, H3PO4 etc.) and oxygen-free acids ( HCl, H 2 S, HCN, etc.).

By basicity, i.e. According to the number of hydrogen atoms in an acid molecule that can be replaced by metal atoms to form a salt, acids are divided into monobasic (for example, HNO 3, HCl), dibasic (H 2 S, H 2 SO 4), tribasic (H 3 PO 4), etc.

The names of oxygen-free acids are derived from the name of the non-metal with the addition of the ending -hydrogen: HCl - hydrochloric acid, H2S e - hydroselenic acid, HCN - hydrocyanic acid.

The names of oxygen-containing acids are also formed from the Russian name of the corresponding element with the addition of the word “acid”. In this case, the name of the acid in which the element is in the highest oxidation state ends in “naya” or “ova”, for example, H2SO4 - sulfuric acid, HClO4 - perchloric acid, H3AsO4 - arsenic acid. With a decrease in the degree of oxidation of the acid-forming element, the endings change in the following sequence: “ovate” ( HClO3 - perchloric acid), “solid” ( HClO2 - chlorous acid), “ovate” ( H O Cl - hypochlorous acid). If an element forms acids while being in only two oxidation states, then the name of the acid corresponding to the lowest oxidation state of the element receives the ending “empty” ( HNO3 - Nitric acid, HNO2 - nitrous acid).

Table - The most important acids and their salts

Obtaining acids

1. Oxygen-free acids can be obtained by direct combination of non-metals with hydrogen:

H 2 + Cl 2 → 2HCl,

H 2 + S H 2 S.

2. Oxygen-containing acids can often be obtained by directly combining acid oxides with water:

SO 3 + H 2 O = H 2 SO 4,

CO 2 + H 2 O = H 2 CO 3,

P 2 O 5 + H 2 O = 2 HPO 3.

3. Both oxygen-free and oxygen-containing acids can be obtained by exchange reactions between salts and other acids:

BaBr 2 + H 2 SO 4 = BaSO 4 + 2HBr,

CuSO 4 + H 2 S = H 2 SO 4 + CuS,

CaCO 3 + 2HBr = CaBr 2 + CO 2 + H 2 O.

4. In some cases, redox reactions can be used to produce acids:

H 2 O 2 + SO 2 = H 2 SO 4,

3P + 5HNO3 + 2H2O = 3H3PO4 + 5NO.

Chemical properties of acids

1. The most characteristic chemical property of acids is their ability to react with bases (as well as basic and amphoteric oxides) to form salts, for example:

H 2 SO 4 + 2NaOH = Na 2 SO 4 + 2H 2 O,

2HNO 3 + FeO = Fe(NO 3) 2 + H 2 O,

2 HCl + ZnO = ZnCl 2 + H 2 O.

2. The ability to interact with some metals in the voltage series up to hydrogen, with the release of hydrogen:

Zn + 2HCl = ZnCl 2 + H 2,

2Al + 6HCl = 2AlCl3 + 3H2.

3. With salts, if a slightly soluble salt or volatile substance is formed:

H 2 SO 4 + BaCl 2 = BaSO 4 ↓ + 2HCl,

2HCl + Na 2 CO 3 = 2NaCl + H 2 O + CO 2,

2KHCO 3 + H 2 SO 4 = K 2 SO 4 +2SO 2+ 2H 2 O.

Note that polybasic acids dissociate stepwise, and the ease of dissociation at each step decreases, therefore, for polybasic acids, instead of medium salts, acidic salts are often formed (in the case of an excess of the reacting acid):

Na 2 S + H 3 PO 4 = Na 2 HPO 4 + H 2 S,

NaOH + H 3 PO 4 = NaH 2 PO 4 + H 2 O.

4. A special case of acid-base interaction is the reaction of acids with indicators, leading to a change in color, which has long been used for the qualitative detection of acids in solutions. So, litmus changes color in an acidic environment to red.

5. When heated, oxygen-containing acids decompose into oxide and water (preferably in the presence of a water-removing agent P2O5):

H 2 SO 4 = H 2 O + SO 3,

H 2 SiO 3 = H 2 O + SiO 2.

M.V. Andryukhova, L.N. Borodina

Let me briefly remind you of specific examples how to properly call salts.

Example 1. The salt K 2 SO 4 is formed by a sulfuric acid residue (SO 4) and metal K. Salts of sulfuric acid are called sulfates. K 2 SO 4 - potassium sulfate.

Example 2. FeCl 3 - the salt contains iron and the remainder of hydrochloric acid(Cl). Name of salt: iron (III) chloride. Please note: in in this case we must not only name the metal, but also indicate its valency (III). In the previous example, this was not necessary, since the valency of sodium is constant.

Important: the name of the salt should indicate the valency of the metal only if the metal has a variable valency!

Example 3. Ba(ClO) 2 - the salt contains barium and the remainder of hypochlorous acid (ClO). Salt name: barium hypochlorite. The valency of the metal Ba in all its compounds is two; it does not need to be indicated.

Example 4. (NH 4) 2 Cr 2 O 7. The NH 4 group is called ammonium, the valence of this group is constant. Name of salt: ammonium dichromate (dichromate).

In the above examples we only encountered the so-called. medium or normal salts. Acidic, basic, double and complex salts, salts of organic acids will not be discussed here.

If you are interested not only in the nomenclature of salts, but also in the methods of their preparation and chemical properties, I recommend that you refer to the relevant sections of the chemistry reference book: "

Acids- electrolytes, upon dissociation of which only H + ions are formed from positive ions:

HNO 3 ↔ H + + NO 3 - ;

CH 3 COOH↔ H + +CH 3 COO — .

All acids are classified into inorganic and organic (carboxylic), which also have their own (internal) classifications.

Under normal conditions, a significant amount of inorganic acids exist in a liquid state, some in a solid state (H 3 PO 4, H 3 BO 3).

Organic acids with up to 3 carbon atoms are highly mobile, colorless liquids with a characteristic pungent odor; acids with 4-9 carbon atoms - oily liquids with unpleasant smell, and acids with a large number of carbon atoms— solids, insoluble in water.

Chemical formulas of acids

Let us consider the chemical formulas of acids using the example of several representatives (both inorganic and organic): hydrochloric acid - HCl, sulfuric acid - H 2 SO 4, phosphoric acid - H 3 PO 4, acetic acid - CH 3 COOH and benzoic acid - C 6 H5COOH. The chemical formula shows the qualitative and quantitative composition of the molecule (how many and which atoms are included in a particular compound). Using the chemical formula, you can calculate the molecular weight of acids (Ar(H) = 1 amu, Ar(Cl) = 35.5 amu. amu, Ar(P) = 31 amu, Ar(O) = 16 amu, Ar(S) = 32 amu, Ar(C) = 12 a.m.):

Mr(HCl) = Ar(H) + Ar(Cl);

Mr(HCl) = 1 + 35.5 = 36.5.

Mr(H 2 SO 4) = 2×Ar(H) + Ar(S) + 4×Ar(O);

Mr(H 2 SO 4) = 2×1 + 32 + 4×16 = 2 + 32 + 64 = 98.

Mr(H 3 PO 4) = 3×Ar(H) + Ar(P) + 4×Ar(O);

Mr(H 3 PO 4) = 3×1 + 31 + 4×16 = 3 + 31 + 64 = 98.

Mr(CH 3 COOH) = 3×Ar(C) + 4×Ar(H) + 2×Ar(O);

Mr(CH 3 COOH) = 3×12 + 4×1 + 2×16 = 36 + 4 + 32 = 72.

Mr(C 6 H 5 COOH) = 7×Ar(C) + 6×Ar(H) + 2×Ar(O);

Mr(C 6 H 5 COOH) = 7 × 12 + 6 × 1 + 2 × 16 = 84 + 6 + 32 = 122.

Structural (graphic) formulas of acids

The structural (graphic) formula of a substance is more visual. It shows how atoms are connected to each other within a molecule. Let us indicate the structural formulas of each of the above compounds:

Rice. 1. Structural formula of hydrochloric acid.

Rice. 2. Structural formula of sulfuric acid.

Rice. 3. Structural formula of phosphoric acid.

Rice. 4. Structural formula of acetic acid.

Rice. 5. Structural formula of benzoic acid.

Ionic formulas

All inorganic acids are electrolytes, i.e. capable of dissociating in an aqueous solution into ions:

HCl ↔ H + + Cl - ;

H 2 SO 4 ↔ 2H + + SO 4 2- ;

H 3 PO 4 ↔ 3H + + PO 4 3- .

Examples of problem solving

EXAMPLE 1

EXAMPLE 2

Acids are chemical compounds that are capable of donating an electrically charged hydrogen ion (cation) and also accepting two interacting electrons, resulting in the formation of a covalent bond.

In this article we will look at the main acids that are studied in middle school. secondary schools, and also learn many interesting facts about a variety of acids. Let's get started.

Acids: types

In chemistry, there are many different acids that have very different properties. Chemists distinguish acids by their oxygen content, volatility, solubility in water, strength, stability, and whether they belong to the organic or inorganic class of chemical compounds. In this article we will look at a table that presents the most famous acids. The table will help you remember the name of the acid and its chemical formula.

So, everything is clearly visible. This table presents the most famous chemical industry acids. The table will help you remember names and formulas much faster.

Hydrogen sulfide acid

H 2 S is hydrosulfide acid. Its peculiarity lies in the fact that it is also a gas. Hydrogen sulfide is very poorly soluble in water, and also interacts with many metals. Hydrogen sulfide acid belongs to the group of “weak acids”, examples of which we will consider in this article.

H 2 S has a slightly sweet taste and also a very strong rotten egg smell. In nature, it can be found in natural or volcanic gases, and it is also released during protein decay.

The properties of acids are very diverse; even if an acid is indispensable in industry, it can be very harmful to human health. This acid is very toxic to humans. When a small amount of hydrogen sulfide is inhaled, a person experiences a headache, severe nausea and dizziness. If a person inhales a large number of H 2 S, it can lead to seizures, coma or even instant death.

Sulfuric acid

H 2 SO 4 is a strong sulfuric acid, which children are introduced to in chemistry lessons in the 8th grade. Chemical acids such as sulfuric acid are very strong oxidizing agents. H 2 SO 4 acts as an oxidizing agent on many metals, as well as basic oxides.

H 2 SO 4 causes chemical burns when it comes into contact with skin or clothing, but it is not as toxic as hydrogen sulfide.

Nitric acid

Strong acids are very important in our world. Examples of such acids: HCl, H 2 SO 4, HBr, HNO 3. HNO 3 is a well-known nitric acid. It has found wide application in industry, as well as in agriculture. It is used to make various fertilizers, in jewelry, when printing photographs, in manufacturing medicines and dyes, as well as in the military industry.

Such chemical acids, like nitrogen, are very harmful to the body. HNO 3 vapors leave ulcers, cause acute inflammation and irritation of the respiratory tract.

Nitrous acid

Nitrous acid is often confused with nitric acid, but there is a difference between them. The fact is that it is much weaker than nitrogen, it has completely different properties and effects on the human body.

HNO 2 has found wide application in the chemical industry.

Hydrofluoric acid

Hydrofluoric acid (or hydrogen fluoride) is a solution of H 2 O with HF. The acid formula is HF. Hydrofluoric acid is very actively used in the aluminum industry. It is used to dissolve silicates, etch silicon and silicate glass.

Hydrogen fluoride is very harmful to the human body; depending on its concentration, it can be a mild narcotic. If it comes into contact with the skin, at first there are no changes, but after a few minutes a sharp pain and chemical burn may appear. Hydrofluoric acid is very harmful to the environment.

Hydrochloric acid

HCl is hydrogen chloride and is a strong acid. Hydrogen chloride retains the properties of acids belonging to the group of strong acids. The acid is transparent and colorless in appearance, but smokes in air. Hydrogen chloride is widely used in the metallurgical and food industries.

This acid causes chemical burns, but getting into the eyes is especially dangerous.

Phosphoric acid

Phosphoric acid (H 3 PO 4) is a weak acid in its properties. But even weak acids can have the properties of strong ones. For example, H 3 PO 4 is used in industry to restore iron from rust. In addition, phosphoric (or orthophosphoric) acid is widely used in agriculture - many different fertilizers are made from it.

The properties of acids are very similar - almost each of them is very harmful to the human body, H 3 PO 4 is no exception. For example, this acid also causes severe chemical burns, nosebleeds, and chipping of teeth.

Carbonic acid

H 2 CO 3 is a weak acid. It is obtained by dissolving CO 2 (carbon dioxide) in H 2 O (water). Carbonic acid is used in biology and biochemistry.

Density of various acids

The density of acids occupies an important place in the theoretical and practical parts chemistry. By knowing the density, you can determine the concentration of a particular acid, solve chemical calculation problems, and add the correct amount of acid to complete the reaction. The density of any acid changes depending on the concentration. For example, the higher the concentration percentage, the higher the density.

General properties of acids

Absolutely all acids are (that is, they consist of several elements of the periodic table), and they necessarily include H (hydrogen) in their composition. Next we will look at which are common:

1. All oxygen-containing acids (in the formula of which O is present) form water upon decomposition, and also oxygen-free acids decompose into simple substances (for example, 2HF decomposes into F 2 and H 2).
2. Oxidizing acids react with all metals in the metal activity series (only those located to the left of H).
3. They interact with various salts, but only with those that were formed by an even weaker acid.

According to their own physical properties acids differ sharply from each other. After all, they can have a smell or not, and also be in a variety of different states of aggregation: liquid, gaseous and even solid. Solid acids are very interesting to study. Examples of such acids: C 2 H 2 0 4 and H 3 BO 3.

Concentration

Concentration is a value that determines the quantitative composition of any solution. For example, chemists often need to determine how much pure sulfuric acid is present in dilute acid H 2 SO 4. To do this, they pour a small amount of dilute acid into a measuring cup, weigh it, and determine the concentration using a density chart. The concentration of acids is closely related to density; often, when determining the concentration, there are calculation problems where you need to determine the percentage of pure acid in a solution.

Classification of all acids according to the number of H atoms in their chemical formula

One of the most popular classifications is the division of all acids into monobasic, dibasic and, accordingly, tribasic acids. Examples of monobasic acids: HNO 3 (nitric), HCl (hydrochloric), HF (hydrofluoric) and others. These acids are called monobasic, since they contain only one H atom. There are many such acids, it is impossible to remember absolutely every one. You just need to remember that acids are classified according to the number of H atoms in their composition. Dibasic acids are defined similarly. Examples: H 2 SO 4 (sulphuric), H 2 S (hydrogen sulfide), H 2 CO 3 (coal) and others. Tribasic: H 3 PO 4 (phosphoric).

Basic classification of acids

One of the most popular classifications of acids is their division into oxygen-containing and oxygen-free. How to remember without knowing chemical formula substances that are oxygen-containing acid?

All oxygen-free acids lack the important element O - oxygen, but they do contain H. Therefore, the word “hydrogen” is always attached to their name. HCl is a H 2 S - hydrogen sulfide.

But you can also write a formula based on the names of acid-containing acids. For example, if the number of O atoms in a substance is 4 or 3, then the suffix -n-, as well as the ending -aya-, is always added to the name:

• H 2 SO 4 - sulfur (number of atoms - 4);
• H 2 SiO 3 - silicon (number of atoms - 3).

If the substance has less than three oxygen atoms or three, then the suffix -ist- is used in the name:

• HNO 2 - nitrogenous;
• H 2 SO 3 - sulfurous.

General properties

All acids taste sour and often slightly metallic. But there are other similar properties that we will now consider.

There are substances called indicators. The indicators change their color, or the color remains, but its shade changes. This occurs when the indicators are affected by other substances, such as acids.

An example of a color change is such a familiar product as tea and citric acid. When lemon is added to tea, the tea gradually begins to noticeably brighten. This is due to the fact that lemon contains citric acid.

There are other examples. Litmus, which is lilac in color in a neutral environment, turns red when hydrochloric acid is added.

When the tensions are in the tension series before hydrogen, gas bubbles are released - H. However, if a metal that is in the tension series after H is placed in a test tube with acid, then no reaction will occur, there will be no gas evolution. So, copper, silver, mercury, platinum and gold will not react with acids.

In this article we reviewed the most famous chemical acids, as well as their main properties and differences.