Formation of names of acids. The most important classes of inorganic substances. Oxides. Hydroxides. Salt. Acids, bases, amphoteric substances. The most important acids and their salts. Genetic relationship of the most important classes of inorganic substances

Acids- complex substances consisting of one or more hydrogen atoms that can be replaced by metal atoms and acidic residues.

Classification of acids

1. By the number of hydrogen atoms: number of hydrogen atoms ( n ) determines the basicity of acids:

n= 1 monobase

n= 2 dibase

n= 3 tribase

2. By composition:

a) Table of oxygen-containing acids, acid residues and corresponding acid oxides:

b) Table of oxygen-free acids

Physical properties of acids

Many acids, such as sulfuric, nitric, and hydrochloric, are colorless liquids. solid acids are also known: orthophosphoric, metaphosphoric HPO 3, boric H 3 BO 3 . Almost all acids are soluble in water. An example of an insoluble acid is silicic acid H2SiO3 . Acid solutions have a sour taste. For example, many fruits are given a sour taste by the acids they contain. Hence the names of acids: citric, malic, etc.

Methods for producing acids

Chemical properties of acids

1. Change the color of the indicators

2. React with metals in the activity series up to H 2

(excl. HNO 3 -Nitric acid)

Video "Interaction of acids with metals"

Me + ACID = SALT + H 2 (r. substitution)

Zn + 2 HCl = ZnCl 2 + H 2

3. With basic (amphoteric) oxides – metal oxides

Video "Interaction of metal oxides with acids"

Fur x O y + ACID = SALT + H 2 O (exchange ruble)

4. React with bases – neutralization reaction

ACID + BASE= SALT+ H 2 O (exchange ruble)

H 3 PO 4 + 3 NaOH = Na 3 PO 4 + 3 H 2 O

5. React with salts of weak, volatile acids - if acid forms, precipitates or gas evolves:

2 NaCl (tv.) + H 2 SO 4 (conc.) = Na 2 SO 4 + 2HCl ( R . exchange )

Video "Interaction of acids with salts"

6. Decomposition of oxygen-containing acids when heated

(excl. H 2 SO 4 ; H 3 P.O. 4 )

ACID = ACID OXIDE + WATER (r. expansion)

Remember!Unstable acids (carbonic and sulfurous acids) - decompose into gas and water:

H 2 CO 3 ↔ H 2 O + CO 2

H 2 SO 3 ↔ H 2 O + SO 2

Hydrogen sulfide acid in products released as gas:

CaS + 2HCl = H 2 S+CaCl2

ASSIGNMENT TASKS

No. 1. Distribute the chemical formulas of acids in a table. Give them names:

LiOH, Mn 2 O 7, CaO, Na 3 PO 4, H 2 S, MnO, Fe (OH) 3, Cr 2 O 3, HI, HClO 4, HBr, CaCl 2, Na 2 O, HCl, H 2 SO 4, HNO 3, HMnO 4, Ca (OH) 2, SiO 2, Acids

Bes-sour-

native

Oxygen-containing

soluble

insoluble

one-

basic

two-basic

three-basic

No. 2. Write down the reaction equations:

Ca + HCl

Na+H2SO4

Al+H2S

Ca+H3PO4
Name the reaction products.

No. 3. Write down reaction equations and name the products:

Na 2 O + H 2 CO 3

ZnO + HCl

CaO + HNO3

Fe 2 O 3 + H 2 SO 4

No. 4. Write down equations for the reactions of acids with bases and salts:

KOH + HNO3

NaOH + H2SO3

Ca(OH) 2 + H 2 S

Al(OH) 3 + HF

HCl + Na 2 SiO 3

H2SO4 + K2CO3

HNO3 + CaCO3

Name the reaction products.

EXERCISES

Trainer No. 1. "Formula and names of acids"

Trainer No. 2. "Establishing correspondence: acid formula - oxide formula"

Safety precautions - First aid in case of acid contact with skin

Safety precautions -

Let's look at the most common acid formulas found in textbooks:

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 valence. 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 valency 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 acidic 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 acidic 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, nitrogenous).

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

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. These are 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 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, citric acid, lactic acid. Let's consider the basic properties of acids.

Physical properties

The physical properties of acids often provide clues 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 a sour taste. Some acids are named after the fruits in which they are found: malic acid, citric acid. Others get their name from the chemical elements they contain.

Classification of acids

Acids are usually classified according to several criteria. The very first one is based on the oxygen content in them. Namely: oxygen-containing (HClO4 - chlorine) and oxygen-free (H2S - hydrogen sulfide).

By number of hydrogen atoms (by basicity):

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

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

Chemical properties

Let's consider the basic chemical properties of acids.

• The first is interaction with indicators. Litmus, methyl orange, phenolphthalein and universal indicator paper are used as indicators. In acid solutions, the color of the indicator will change color: litmus and universal ind. the paper will turn red, methyl orange will turn pink, phenolphthalein will remain colorless.
• The second is the interaction of acids with bases. This reaction is also called neutralization. An acid reacts with a 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. A neutralization reaction also occurs here. Basic oxides are close “relatives” of bases, therefore the reaction is the same. We use these oxidizing properties of acids very often. For example, to remove rust from pipes. The acid reacts with the oxide to form a soluble salt.
• Fourth - 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 capable of reacting with all inactive metals, while citric and oxalic acids are so weak that they react very slowly even with active metals.
• Fifth, the reaction of oxygen-containing acids to heating. Almost all acids in this group decompose when heated into oxygen oxide and water. The exceptions are carbonic acid (H3PO4) and sulfurous acid (H2SO4). When heated, they break down into water and gas. This must be remembered. That's all the basic properties of acids.

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

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