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 oxidation degree 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 “iste” ( HNO3 - Nitric acid, HNO2 - nitrous acid).

Table - The most important acids and their salts

Acid

Names of the corresponding normal salts

Name

Formula

Nitrogen

HNO3

Nitrates

Nitrogenous

HNO2

Nitrites

Boric (orthoboric)

H3BO3

Borates (orthoborates)

Hydrobromic

Bromides

Hydroiodide

Iodides

Silicon

H2SiO3

Silicates

Manganese

HMnO4

Permanganates

Metaphosphoric

HPO 3

Metaphosphates

Arsenic

H3AsO4

Arsenates

Arsenic

H3AsO3

Arsenites

Orthophosphoric

H3PO4

Orthophosphates (phosphates)

Diphosphoric (pyrophosphoric)

H4P2O7

Diphosphates (pyrophosphates)

Dichrome

H2Cr2O7

Dichromats

Sulfuric

H2SO4

Sulfates

Sulphurous

H2SO3

Sulfites

Coal

H2CO3

Carbonates

Phosphorous

H3PO3

Phosphites

Hydrofluoric (fluoric)

Fluorides

Hydrochloric (salt)

Chlorides

Chlorine

HClO4

Perchlorates

Chlorous

HClO3

Chlorates

Hypochlorous

HClO

Hypochlorites

Chrome

H2CrO4

Chromates

Hydrogen cyanide (cyanic)

Cyanide

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


Acid formulasNames of acidsNames of the corresponding salts
HClO4 chlorine perchlorates
HClO3 hypochlorous chlorates
HClO2 chloride chlorites
HClO hypochlorous hypochlorites
H5IO6 iodine periodates
HIO 3 iodic iodates
H2SO4 sulfuric sulfates
H2SO3 sulfurous sulfites
H2S2O3 thiosulfur thiosulfates
H2S4O6 tetrathionic tetrathionates
HNO3 nitrogen nitrates
HNO2 nitrogenous nitrites
H3PO4 orthophosphoric orthophosphates
HPO 3 metaphosphoric metaphosphates
H3PO3 phosphorous phosphites
H3PO2 phosphorous hypophosphites
H2CO3 coal carbonates
H2SiO3 silicon silicates
HMnO4 manganese permanganates
H2MnO4 manganese manganates
H2CrO4 chrome chromates
H2Cr2O7 dichrome dichromats
HF hydrogen fluoride (fluoride) fluorides
HCl hydrochloric (hydrochloric) chlorides
HBr hydrobromic bromides
HI hydrogen iodide iodides
H2S hydrogen sulfide sulfides
HCN hydrogen cyanide cyanides
HOCN cyan cyanates

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 this case we must not only name the metal, but also indicate its valence (III). In the previous example, this was not necessary, since the valence of sodium is constant.

Important: the name of the salt should indicate the valence 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 turning to the relevant sections of the chemistry reference book: "

Acids are complex substances whose molecules include hydrogen atoms that can be replaced or exchanged for metal atoms and an acid residue.

Based on the presence or absence of oxygen in the molecule, acids are divided into oxygen-containing(H 2 SO 4 sulfuric acid, H 2 SO 3 sulfurous acid, HNO 3 nitric acid, H 3 PO 4 phosphoric acid, H 2 CO 3 carbonic acid, H 2 SiO 3 silicic acid) and oxygen-free(HF hydrofluoric acid, HCl hydrochloric acid (hydrochloric acid), HBr hydrobromic acid, HI hydroiodic acid, H 2 S hydrosulfide acid).

Depending on the number of hydrogen atoms in the acid molecule, acids are monobasic (with 1 H atom), dibasic (with 2 H atoms) and tribasic (with 3 H atoms). For example, nitric acid HNO 3 is monobasic, since its molecule contains one hydrogen atom, sulfuric acid H 2 SO 4 – dibasic, etc.

There are very few inorganic compounds containing four hydrogen atoms that can be replaced by a metal.

The part of an acid molecule without hydrogen is called an acid residue.

Acidic residues may consist of one atom (-Cl, -Br, -I) - these are simple acidic residues, or they may consist of a group of atoms (-SO 3, -PO 4, -SiO 3) - these are complex residues.

In aqueous solutions, during exchange and substitution reactions, acidic residues are not destroyed:

H 2 SO 4 + CuCl 2 → CuSO 4 + 2 HCl

The word anhydride means anhydrous, that is, an acid without water. For example,

H 2 SO 4 – H 2 O → SO 3. Anoxic acids do not have anhydrides.

Acids get their name from the name of the acid-forming element (acid-forming agent) with the addition of the endings “naya” and less often “vaya”: H 2 SO 4 - sulfuric; H 2 SO 3 – coal; H 2 SiO 3 – silicon, etc.

The element can form several oxygen acids. In this case, the indicated endings in the names of acids will be when the element exhibits a higher valence (the acid molecule contains a high content of oxygen atoms). If the element exhibits a lower valence, the ending in the name of the acid will be “empty”: HNO 3 - nitric, HNO 2 - nitrogenous.

Acids can be obtained by dissolving anhydrides in water. If the anhydrides are insoluble in water, the acid can be obtained by the action of another stronger acid on the salt of the required acid. This method is typical for both oxygen and oxygen-free acids. Oxygen-free acids are also obtained by direct synthesis from hydrogen and a non-metal, followed by dissolving the resulting compound in water:

H 2 + Cl 2 → 2 HCl;

H 2 + S → H 2 S.

Solutions of the resulting gaseous substances HCl and H 2 S are acids.

Under normal conditions, acids exist in both liquid and solid states.

Chemical properties of acids

Acid solutions act on indicators. All acids (except silicic) are highly soluble in water. Special substances - indicators allow you to determine the presence of acid.

Indicators are substances of complex structure. They change their color depending on their interaction with different chemicals. In neutral solutions they have one color, in solutions of bases they have another color. When interacting with an acid, they change their color: the methyl orange indicator turns red, and the litmus indicator also turns red.

Interact with bases with the formation of water and salt, which contains an unchanged acid residue (neutralization reaction):

H 2 SO 4 + Ca(OH) 2 → CaSO 4 + 2 H 2 O.

Interact with base oxides with the formation of water and salt (neutralization reaction). The salt contains the acid residue of the acid that was used in the neutralization reaction:

H 3 PO 4 + Fe 2 O 3 → 2 FePO 4 + 3 H 2 O.

Interact with metals. For acids to interact with metals, certain conditions must be met:

1. the metal must be sufficiently active in relation to acids (in the series of activity of metals it must be located before hydrogen). The further to the left a metal is in the activity series, the more intensely it interacts with acids;

2. the acid must be strong enough (that is, capable of donating hydrogen ions H +).

When chemical reactions of acid with metals occur, salt is formed and hydrogen is released (except for the interaction of metals with nitric and concentrated sulfuric acids):

Zn + 2HCl → ZnCl 2 + H 2 ;

Cu + 4HNO 3 → CuNO 3 + 2 NO 2 + 2 H 2 O.

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Acids can be classified based on 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 being split off from the acid molecule during dissociation in the form of hydrogen cations H +, and also replaced by metal atoms:

4) Solubility

5) Stability

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 right-pointing arrow () or an equal sign (=) is used, which shows the virtual irreversibility of such dissociation. For example, the dissociation equation for strong hydrochloric acid can be written in two ways:

or in this form: HCl = H + + Cl -

or in this way: HCl → H + + Cl -

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

If we want to write the dissociation equation for a weak monoprotic acid, we must use two arrows in the equation instead of the sign. 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 stepwise, i.e. Hydrogen cations are separated from their molecules not simultaneously, but one by one. 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 occurs in three steps with the alternating separation 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 subsequent stage of dissociation occurs 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, the exception is sulfuric acid. Since this acid dissociates well in both stages, 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 is their oxidizing properties. It was stated that acids are weak oxidizing agents and strong oxidizing agents. The vast majority of acids (almost all except H 2 SO 4 (conc.) and HNO 3) are weak oxidizing agents, since they can only exhibit their oxidizing ability due to hydrogen cations. Such acids can oxidize only those metals that are in the activity series to the left of hydrogen, and the products form a salt of the corresponding metal and hydrogen. For example:

H 2 SO 4 (diluted) + 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 all metals before 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 low-active metals such as copper, mercury, and silver. The interaction of nitric acid and concentrated sulfuric acid with metals, as well as some other substances, due to their specificity, will be discussed 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 H 2 O + NaCl

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

5. Interaction of acids with salts

This reaction occurs if a precipitate, gas, or a significantly weaker acid is formed than the one that reacts. 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 oxidative 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 located before hydrogen in the activity series, but also almost all metals after it (except platinum and gold).

For example, they are capable of oxidizing copper, silver and mercury. However, one should firmly grasp the fact that a number of metals (Fe, Cr, Al), despite the fact that they are quite active (available before hydrogen), nevertheless do not react with concentrated HNO 3 and concentrated H 2 SO 4 without heating due to the phenomenon of passivation - 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 occur. However, with strong heating, the reaction still occurs.

In the case of interaction with metals, the obligatory 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 reaction temperature.

The high oxidizing ability of concentrated sulfuric and concentrated nitric acids allows them to react not only with practically all metals of the activity series, 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 oxygen-free acids

All oxygen-free acids (except HF) can exhibit reducing properties due to chemical element, which is part of the anion, under the action of various oxidizing agents. For example, all hydrohalic acids (except HF) are oxidized by manganese dioxide, potassium permanganate, and 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

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

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 according to their oxygen content, volatility, solubility in water, strength, stability, whether they are 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 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 awakens headache, severe nausea and dizziness begin. 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 and, depending on its concentration, can be a mild narcotic. In case of contact with the skin, there are no changes at first, but after a few minutes it may appear. sharp pain and chemical burn. Hydrofluoric acid is very harmful to the environment.

Hydrochloric acid

HCl is hydrogen chloride and is 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 of 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. 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 physical states: 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 the chemical formula of a substance, that it is an oxygen-containing acid?

All oxygen-free acids do not contain important element O is oxygen, but it contains 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 lemon 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 in a neutral environment has purple colour 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 examined the most famous chemical acids, as well as their main properties and differences.