All about acids. Names of some inorganic acids and salts

Do not underestimate the role of acids in our lives, because many of them are simply irreplaceable in Everyday life. First, let's remember what acids are. This complex substances. The formula is written as follows: HnA, where H is hydrogen, n is the number of atoms, A is the acid residue.

The main properties of acids include the ability to replace the molecules of hydrogen atoms with metal atoms. Most of them are not only caustic, but also very poisonous. But there are also those that we encounter constantly, without harm to our health: vitamin C, lemon acid, lactic acid. Consider the basic properties of acids.

Physical properties

The physical properties of acids often provide a clue to their character. Acids can exist in three forms: solid, liquid and gaseous. For example: nitric (HNO3) and sulfuric acid (H2SO4) are colorless liquids; boric (H3BO3) and metaphosphoric (HPO3) are solid acids. Some of them have color and smell. Different acids dissolve differently in water. There are also insoluble ones: H2SiO3 - silicon. Liquid substances have sour taste. The name of some acids was given by the fruits in which they are found: malic acid, citric acid. Others got their name from the chemical elements contained in them.

Acid classification

Usually acids are classified according to several criteria. The very first is, according to the oxygen content in them. Namely: oxygen-containing (HClO4 - chlorine) and anoxic (H2S - hydrogen sulfide).

By the number of hydrogen atoms (by basicity):

• Monobasic - contains one hydrogen atom (HMnO4);
• Dibasic - has two hydrogen atoms (H2CO3);
• Tribasic, respectively, have three hydrogen atoms (H3BO);
• Polybasic - have four or more atoms, are rare (H4P2O7).

By class chemical compounds, divided into organic and inorganic acids. The former are mainly found in plant products: acetic, lactic, nicotinic, ascorbic acids. Inorganic acids include: sulfuric, nitric, boric, arsenic. The range of their application is quite wide from industrial needs (production of dyes, electrolytes, ceramics, fertilizers, etc.) to cooking or cleaning sewers. Acids can also be classified according to strength, volatility, stability and solubility in water.

Chemical properties

Consider the main Chemical properties acids.

• The first is interaction with indicators. As indicators, litmus, methyl orange, phenolphthalein and universal indicator paper are used. In acid solutions, the color of the indicator will change color: litmus and universal ind. paper will turn red, methyl orange - pink, phenolphthalein will remain colorless.
• The second is the interaction of acids with bases. This reaction is also called neutralization. The acid reacts with the base, resulting in salt + water. For example: H2SO4+Ca(OH)2=CaSO4+2 H2O.
• Since almost all acids are highly soluble in water, neutralization can be carried out with both soluble and insoluble bases. The exception is silicic acid, which is almost insoluble in water. To neutralize it, bases such as KOH or NaOH are required (they are soluble in water).
• The third is the interaction of acids with basic oxides. This is where the neutralization reaction takes place. Basic oxides are close "relatives" of bases, hence the reaction is the same. We very often use these oxidizing properties of acids. For example, to remove rust from pipes. The acid reacts with the oxide to become a soluble salt.
• The fourth is the reaction with metals. Not all metals react equally well with acids. They are divided into active (K, Ba, Ca, Na, Mg, Al, Mn, Zn, Cr, Fe, Ni, Sn. Pb) and inactive (Cu, Hg, Ag, Pt, Au). It is also worth paying attention to the strength of the acid (strong, weak). For example, hydrochloric and sulfuric acids are able to react with all inactive metals, while citric and oxalic acids are so weak that they react very slowly even with active metals.
• The fifth is the reaction of oxygen-containing acids to heating. Almost all acids of this group, when heated, decompose into oxygen oxide and water. The exceptions are carbonic (H3PO4) and sulfurous acids (H2SO4). When heated, they decompose into water and gas. This must be remembered. That's all the basic properties of acids.

Acids are such chemical compounds that are able to donate an electrically charged hydrogen ion (cation) and also accept two interacting electrons, as a result of which a covalent bond is formed.

In this article, we will look at the main acids that are studied in the middle classes. general education schools, and also find out the set interesting facts on various acids. Let's get started.

Acids: types

In chemistry, there are many different acids that have the most different properties. Chemists distinguish acids by their oxygen content, volatility, solubility in water, strength, stability, belonging to an organic or inorganic class 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 acids in the chemical industry. The table will help you remember the names and formulas much faster.

Hydrosulphuric 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. Hydrosulphuric 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 a very strong smell of rotten eggs. In nature, it can be found in natural or volcanic gases, and it is also released when protein rots.

The properties of acids are very diverse, even if the acid is indispensable in industry, it can be very unhealthy for human health. This acid is highly toxic to humans. When a small amount of hydrogen sulfide is inhaled, a person awakens headache, severe nausea and dizziness begin. If a person breathes a large number of H 2 S, this can lead to convulsions, coma or even instant death.

Sulfuric acid

H 2 SO 4 is a strong sulfuric acid that children get acquainted with in chemistry lessons as early as the 8th grade. Chemical acids such as sulfuric 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 on contact with skin or clothing, but 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 the well-known nitric acid. It has found wide application in industry as well as in agriculture. It is used for the manufacture of various fertilizers, in jewelry, in printing photographs, in the production of medicines and dyes, as well as in the military industry.

Chemical acids such as nitric acid are very harmful to the body. Vapors of HNO 3 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 formula of the acid is HF. Hydrofluoric acid is very actively used in aluminum industry. It dissolves silicates, etchs silicon, silicate glass.

Hydrogen fluoride is very harmful to the human body, depending on its concentration it can be a light drug. When it comes into contact with the skin, at first there are no changes, but after a few minutes, a sharp pain and a 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. In appearance, the acid is transparent and colorless, but smokes in air. Hydrogen chloride is widely used in the metallurgical and food industries.

This acid causes chemical burns, but it is especially dangerous if it gets into the eyes.

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 recover iron from rust. In addition, phosphoric (or phosphoric) acid is widely used in agriculture - a wide variety of 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 tooth decay.

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. Thanks to the knowledge of density, it is possible to determine the concentration of a particular acid, solve chemical problems and add the correct amount of acid to complete the reaction. The density of any acid varies with concentration. For example, the greater the percentage of concentration, the greater the density.

General properties of acids

Absolutely all acids are (that is, they consist of several elements of the periodic table), while 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 when decomposed, and also anoxic acids decompose into simple substances(for example, 2HF decomposes into F 2 and H 2).
2. Oxidizing acids interact with all metals in the metal activity series (only with 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.

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

Concentration

Concentration is a quantity that determines the quantitative composition of any solution. For example, chemists often need to determine how much pure sulfuric acid is in dilute H 2 SO 4 acid. To do this, they pour a small amount of dilute acid into a beaker, weigh it, and determine the concentration from a density chart. The concentration of acids is closely related to the density, often there are calculation tasks to determine the concentration, where you need to determine the percentage of pure acid in the 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 only one H atom is present in their composition. There are many such acids, it is impossible to remember absolutely every one. You just need to remember that acids are also classified by 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 anoxic acids. How to remember, without knowing the chemical formula of a substance, that it is an oxygen-containing acid?

All oxygen-free acids in the composition lack the important element O - oxygen, but they contain H. Therefore, the word "hydrogen" is always attributed to their name. HCl is a H 2 S - hydrogen sulfide.

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

• H 2 SO 4 - sulfuric (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, which we will now consider.

There are substances that are called indicators. Indicators change their color, or the color remains, but its hue changes. This happens when some other substances, such as acids, act on the indicators.

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

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

With tensions up to hydrogen in the series, 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 examined the most famous chemical acids, as well as their main properties and differences.

Let me briefly remind you with specific examples of how salts should be properly named.

Example 1. Salt K 2 SO 4 is formed by the rest of sulfuric acid (SO 4) and metal K. Salts of sulfuric acid are called sulfates. K 2 SO 4 - potassium sulfate.

Example 2. FeCl 3 - the composition of the salt includes iron and the rest of hydrochloric acid (Cl). Name of the salt: iron(III) chloride. Please note: in this case, we not only have to 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: in the name of the salt, the valency of the metal should be indicated only if this metal has a variable valency!

Example 3. Ba (ClO) 2 - the composition of the salt includes barium and the remainder of hypochlorous acid (ClO). Name of salt: barium hypochlorite. The valency of the Ba metal in all its compounds is two, it is not necessary to indicate it.

Example 4. (NH 4) 2 Cr 2 O 7. The NH 4 group is called ammonium, the valency of this group is constant. Salt name: ammonium dichromate (bichromate).

In the above examples, we met only the so-called. medium or normal salts. Acid, 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 for their preparation and chemical properties, I recommend that you refer to the relevant sections of the reference book on chemistry: "

Acids can be classified according to different criteria:

1) The presence of oxygen atoms in the acid

2) Acid basicity

The basicity of an acid is the number of "mobile" hydrogen atoms in its molecule, capable of splitting off from the acid molecule in the form of hydrogen cations H + during dissociation, and also being replaced by metal atoms:

4) Solubility

5) Sustainability

7) Oxidizing properties

Chemical properties of acids

1. Ability to dissociate

Acids dissociate in aqueous solutions into hydrogen cations and acid residues. As already mentioned, acids are divided into well-dissociating (strong) and low-dissociating (weak). When writing the dissociation equation for strong monobasic acids, either one arrow pointing to the right () or an equal sign (=) is used, which actually shows the irreversibility of such dissociation. For example, the dissociation equation for strong hydrochloric acid can be written in two ways:

or in this form: HCl \u003d H + + Cl -

or in this: HCl → H + + Cl -

In fact, the direction of the arrow tells us that the reverse process of combining hydrogen cations with acidic residues (association) in strong acids practically does not occur.

In case we want to write the equation for the dissociation of a weak monobasic acid, we must use two arrows instead of the sign in the equation. This sign reflects the reversibility of the dissociation of weak acids - in their case, the reverse process of combining hydrogen cations with acidic residues is strongly pronounced:

CH 3 COOH CH 3 COO - + H +

Polybasic acids dissociate in steps, i.e. hydrogen cations are not detached from their molecules simultaneously, but in turn. For this reason, the dissociation of such acids is expressed not by one, but by several equations, the number of which is equal to the basicity of the acid. For example, the dissociation of tribasic phosphoric acid proceeds in three steps with the successive detachment of H + cations:

H 3 PO 4 H + + H 2 PO 4 —

H 2 PO 4 - H + + HPO 4 2-

HPO 4 2- H + + PO 4 3-

It should be noted that each next stage of dissociation proceeds to a lesser extent than the previous one. That is, H 3 PO 4 molecules dissociate better (to a greater extent) than H 2 PO 4 — ions, which, in turn, dissociate better than HPO 4 2- ions. This phenomenon is associated with an increase in the charge of acidic residues, as a result of which the strength of the bond between them and positive H + ions increases.

Of the polybasic acids, sulfuric acid is an exception. Since this acid dissociates well in both steps, it is permissible to write the equation of its dissociation in one stage:

H 2 SO 4 2H + + SO 4 2-

2. Interaction of acids with metals

The seventh point in the classification of acids, we indicated their oxidizing properties. It was pointed out that acids are weak oxidizers and strong oxidizers. The vast majority of acids (practically all except H 2 SO 4 (conc.) and HNO 3) are weak oxidizing agents, since they can show their oxidizing ability only due to hydrogen cations. Such acids can oxidize from metals only those that are in the activity series to the left of hydrogen, while the salt of the corresponding metal and hydrogen are formed as products. For example:

H 2 SO 4 (diff.) + Zn ZnSO 4 + H 2

2HCl + Fe FeCl 2 + H 2

As for strong oxidizing acids, i.e. H 2 SO 4 (conc.) and HNO 3, then the list of metals on which they act is much wider, and it includes both all metals up to hydrogen in the activity series, and almost everything after. That is, concentrated sulfuric acid and nitric acid of any concentration, for example, will oxidize even such inactive metals as copper, mercury, and silver. In more detail, the interaction of nitric acid and concentrated sulfuric acid with metals, as well as some other substances due to their specificity, will be considered separately at the end of this chapter.

3. Interaction of acids with basic and amphoteric oxides

Acids react with basic and amphoteric oxides. Silicic acid, since it is insoluble, does not react with low-active basic oxides and amphoteric oxides:

H 2 SO 4 + ZnO ZnSO 4 + H 2 O

6HNO 3 + Fe 2 O 3 2Fe (NO 3) 3 + 3H 2 O

H 2 SiO 3 + FeO ≠

4. Interaction of acids with bases and amphoteric hydroxides

HCl + NaOH H2O + NaCl

3H 2 SO 4 + 2Al (OH) 3 Al 2 (SO 4) 3 + 6H 2 O

5. Interaction of acids with salts

This reaction proceeds if a precipitate, a gas, or a substantially weaker acid than the one that reacts is formed. For example:

H 2 SO 4 + Ba(NO 3) 2 BaSO 4 ↓ + 2HNO 3

CH 3 COOH + Na 2 SO 3 CH 3 COONa + SO 2 + H 2 O

HCOONa + HCl HCOOH + NaCl

6. Specific oxidizing properties of nitric and concentrated sulfuric acids

As mentioned above, nitric acid in any concentration, as well as sulfuric acid exclusively in a concentrated state, are very strong oxidizing agents. In particular, unlike other acids, they oxidize not only metals that are up to hydrogen in the activity series, but also almost all metals after it (except platinum and gold).

For example, they are able to oxidize copper, silver and mercury. However, it should be firmly grasped the fact that a number of metals (Fe, Cr, Al), despite the fact that they are quite active (they are up to hydrogen), nevertheless, do not react with concentrated HNO 3 and concentrated H 2 SO 4 without heating on due to the passivation phenomenon - a protective film of solid oxidation products is formed on the surface of such metals, which does not allow molecules of concentrated sulfuric and concentrated nitric acids to penetrate deep into the metal for the reaction to proceed. However, with strong heating, the reaction still proceeds.

In the case of interaction with metals, the required products are always the salt of the corresponding metal and the acid used, as well as water. A third product is also always isolated, the formula of which depends on many factors, in particular, such as the activity of metals, as well as the concentration of acids and the temperature of the reactions.

The high oxidizing power of concentrated sulfuric and concentrated nitric acids allows them to react not only with practically all metals of the activity range, but even with many solid non-metals, in particular, with phosphorus, sulfur, and carbon. The table below clearly shows the products of the interaction of sulfuric and nitric acids with metals and non-metals, depending on the concentration:

7. Reducing properties of anoxic acids

All anoxic acids (except HF) can exhibit reducing properties due to the chemical element that is part of the anion, under the action of various oxidizing agents. So, for example, all hydrohalic acids (except HF) are oxidized by manganese dioxide, potassium permanganate, potassium dichromate. In this case, halide ions are oxidized to free halogens:

4HCl + MnO 2 MnCl 2 + Cl 2 + 2H 2 O

18HBr + 2KMnO 4 2KBr + 2MnBr 2 + 8H 2 O + 5Br 2

14НI + K 2 Cr 2 O 7 3I 2 ↓ + 2Crl 3 + 2KI + 7H 2 O

Among all hydrohalic acids, hydroiodic acid has the greatest reducing activity. Unlike other hydrohalic acids, even ferric oxide and salts can oxidize it.

6HI ​​+ Fe 2 O 3 2FeI 2 + I 2 ↓ + 3H 2 O

2HI + 2FeCl 3 2FeCl 2 + I 2 ↓ + 2HCl

Hydrosulfide acid H 2 S also has a high reducing activity. Even an oxidizing agent such as sulfur dioxide can oxidize it.