7. Acids. Salt. Relationship between classes of inorganic substances

7.1. acids

Acids are electrolytes, during the dissociation of which only hydrogen cations H + are formed as positively charged ions (more precisely, hydronium ions H 3 O +).

Another definition: acids are complex substances consisting of a hydrogen atom and acid residues (Table 7.1).

Table 7.1

Formulas and names of some acids, acid residues and salts

Acid Formula	Name of the acid	Acid residue (anion)	Name of salts (medium)
HF	Hydrofluoric (hydrofluoric)	F-	Fluorides
HCl	Hydrochloric (hydrochloric)	Cl-	chlorides
HBr	Hydrobromic	Br-	Bromides
HI	Hydroiodic	I-	iodides
H 2 S	Hydrogen sulfide	S2−	Sulfides
H2SO3	sulphurous	SO 3 2 -	Sulfites
H2SO4	sulfuric	SO 4 2 -	sulfates
HNO 2	nitrogenous	NO 2 -	Nitrites
HNO3	Nitrogen	NO 3 -	Nitrates
H2SiO3	Silicon	SiO 3 2 -	silicates
HPO 3	Metaphosphoric	PO 3 -	Metaphosphates
H3PO4	orthophosphoric	PO 4 3 -	Orthophosphates (phosphates)
H4P2O7	Pyrophosphoric (two-phosphoric)	P 2 O 7 4 -	Pyrophosphates (diphosphates)
HMnO 4	manganese	MnO 4 -	Permanganates
H2CrO4	Chrome	CrO 4 2 -	Chromates
H2Cr2O7	dichrome	Cr 2 O 7 2 -	Dichromates (bichromates)
H 2 SeO 4	Selenic	SeO 4 2 −	selenates
H3BO3	Bornaya	BO 3 3 -	Orthoborates
HClO	hypochlorous	ClO-	Hypochlorites
HClO 2	Chloride	ClO 2 -	Chlorites
HClO 3	Chlorine	ClO 3 -	Chlorates
HClO 4	Chloric	ClO 4 -	Perchlorates
H2CO3	Coal	CO 3 3 -	Carbonates
CH3COOH	Acetic	CH 3 COO −	Acetates
HCOOH	Formic	HCOO-	Formates

Under normal conditions, acids can be solids (H 3 PO 4 , H 3 BO 3 , H 2 SiO 3 ) and liquids (HNO 3 , H 2 SO 4 , CH 3 COOH). These acids can exist both in individual (100% form) and in the form of dilute and concentrated solutions. For example, H 2 SO 4 , HNO 3 , H 3 PO 4 , CH 3 COOH are known both individually and in solutions.

A number of acids are known only in solutions. These are all hydrohalic (HCl, HBr, HI), hydrogen sulfide H 2 S, hydrocyanic (hydrocyanic HCN), coal H 2 CO 3, sulfurous H 2 SO 3 acid, which are solutions of gases in water. For example, hydrochloric acid is a mixture of HCl and H 2 O, coal is a mixture of CO 2 and H 2 O. It is clear that using the expression “solution of hydrochloric acid" not right.

Most acids are soluble in water, silicic acid H 2 SiO 3 is insoluble. The vast majority of acids have a molecular structure. Examples of structural formulas of acids:

In most oxygen-containing acid molecules, all hydrogen atoms are bonded to oxygen. But there are exceptions:

Acids are classified according to a number of features (Table 7.2).

Table 7.2

Acid classification

Classification sign	Acid type	Examples
The number of hydrogen ions formed during the complete dissociation of an acid molecule	Monobasic	HCl, HNO 3 , CH 3 COOH
	Dibasic	H 2 SO 4 , H 2 S, H 2 CO 3
	Tribasic	H 3 PO 4 , H 3 AsO 4
The presence or absence of an oxygen atom in the molecule	Oxygen-containing (acid hydroxides, oxoacids)	HNO 2 , H 2 SiO 3 , H 2 SO 4
	Anoxic	HF, H2S, HCN
Degree of dissociation (strength)	Strong (completely dissociate, strong electrolytes)	HCl, HBr, HI, H 2 SO 4 (diff), HNO 3 , HClO 3 , HClO 4 , HMnO 4 , H 2 Cr 2 O 7
	Weak (partially dissociate, weak electrolytes)	HF, HNO 2 , H 2 SO 3 , HCOOH, CH 3 COOH, H 2 SiO 3 , H 2 S, HCN, H 3 PO 4 , H 3 PO 3 , HClO, HClO 2 , H 2 CO 3 , H 3 BO 3, H 2 SO 4 (conc)
Oxidizing properties	Oxidizing agents due to H + ions (conditionally non-oxidizing acids)	HCl, HBr, HI, HF, H 2 SO 4 (diff), H 3 PO 4 , CH 3 COOH
	Oxidizing agents due to the anion (oxidizing acids)	HNO 3, HMnO 4, H 2 SO 4 (conc), H 2 Cr 2 O 7
	Anion Reducing Agents	HCl, HBr, HI, H 2 S (but not HF)
Thermal stability	Exists only in solutions	H 2 CO 3 , H 2 SO 3 , HClO, HClO 2
	Easily decomposed when heated	H 2 SO 3 , HNO 3 , H 2 SiO 3
	Thermally stable	H 2 SO 4 (conc), H 3 PO 4

All the general chemical properties of acids are due to the presence in their aqueous solutions of an excess of hydrogen cations H + (H 3 O +).

1. Due to an excess of H + ions, aqueous solutions of acids change the color of violet and methyl orange litmus to red (phenolphthalein does not change color, remains colorless). In an aqueous solution of weak carbonic acid, the litmus is not red, but pink; a solution over a precipitate of very weak silicic acid does not change the color of the indicators at all.

2. Acids interact with basic oxides, bases and amphoteric hydroxides, ammonia hydrate (see Ch. 6).

Example 7.1. To carry out the transformation BaO → BaSO 4, you can use: a) SO 2; b) H 2 SO 4; c) Na 2 SO 4; d) SO3.

Decision. The transformation can be carried out using H 2 SO 4:

BaO + H 2 SO 4 \u003d BaSO 4 ↓ + H 2 O

BaO + SO 3 = BaSO 4

Na 2 SO 4 does not react with BaO, and in the reaction of BaO with SO 2 barium sulfite is formed:

BaO + SO 2 = BaSO 3

Answer: 3).

3. Acids react with ammonia and its aqueous solutions to form ammonium salts:

HCl + NH 3 \u003d NH 4 Cl - ammonium chloride;

H 2 SO 4 + 2NH 3 = (NH 4) 2 SO 4 - ammonium sulfate.

4. Non-oxidizing acids with the formation of a salt and the release of hydrogen react with metals located in the row of activity to hydrogen:

H 2 SO 4 (diff) + Fe = FeSO 4 + H 2

2HCl + Zn \u003d ZnCl 2 \u003d H 2

The interaction of oxidizing acids (HNO 3 , H 2 SO 4 (conc)) with metals is very specific and is considered in the study of the chemistry of elements and their compounds.

5. Acids interact with salts. The reaction has a number of features:

a) in most cases, when a stronger acid reacts with a salt of a weaker acid, a salt of a weak acid is formed and a weak acid, or, as they say, a stronger acid displaces a weaker one. The series of decreasing strength of acids looks like this:

Examples of ongoing reactions:

2HCl + Na 2 CO 3 \u003d 2NaCl + H 2 O + CO 2

H 2 CO 3 + Na 2 SiO 3 = Na 2 CO 3 + H 2 SiO 3 ↓

2CH 3 COOH + K 2 CO 3 \u003d 2CH 3 COOK + H 2 O + CO 2

3H 2 SO 4 + 2K 3 PO 4 = 3K 2 SO 4 + 2H 3 PO 4

Do not interact with each other, for example, KCl and H 2 SO 4 (diff), NaNO 3 and H 2 SO 4 (diff), K 2 SO 4 and HCl (HNO 3, HBr, HI), K 3 PO 4 and H 2 CO 3 , CH 3 COOK and H 2 CO 3 ;

b) in some cases, a weaker acid displaces a stronger one from the salt:

CuSO 4 + H 2 S \u003d CuS ↓ + H 2 SO 4

3AgNO 3 (razb) + H 3 PO 4 = Ag 3 PO 4 ↓ + 3HNO 3.

Such reactions are possible when the precipitates of the resulting salts do not dissolve in the resulting dilute strong acids (H 2 SO 4 and HNO 3);

c) in the case of the formation of precipitates that are insoluble in strong acids, a reaction between a strong acid and a salt formed by another strong acid is possible:

BaCl 2 + H 2 SO 4 \u003d BaSO 4 ↓ + 2HCl

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

AgNO 3 + HCl = AgCl↓ + HNO 3

Example 7.2. Indicate the series in which the formulas of substances that react with H 2 SO 4 are given (diff).

1) Zn, Al 2 O 3, KCl (p-p); 3) NaNO 3 (p-p), Na 2 S, NaF; 2) Cu (OH) 2, K 2 CO 3, Ag; 4) Na 2 SO 3, Mg, Zn (OH) 2.

Decision. All substances of series 4 interact with H 2 SO 4 (razb):

Na 2 SO 3 + H 2 SO 4 \u003d Na 2 SO 4 + H 2 O + SO 2

Mg + H 2 SO 4 \u003d MgSO 4 + H 2

Zn(OH) 2 + H 2 SO 4 = ZnSO 4 + 2H 2 O

In row 1) the reaction with KCl (p-p) is not feasible, in row 2) - with Ag, in row 3) - with NaNO 3 (p-p).

Answer: 4).

6. Concentrated sulfuric acid behaves very specifically in reactions with salts. It is a non-volatile and thermally stable acid, therefore it displaces all strong acids from solid (!) Salts, since they are more volatile than H 2 SO 4 (conc):

KCl (tv) + H 2 SO 4 (conc) KHSO 4 + HCl

2KCl (tv) + H 2 SO 4 (conc) K 2 SO 4 + 2HCl

Salts formed by strong acids (HBr, HI, HCl, HNO 3, HClO 4) react only with concentrated sulfuric acid and only in the solid state

Example 7.3. Concentrated sulfuric acid, unlike dilute sulfuric acid, reacts:

3) KNO 3 (TV);

Decision. Both acids react with KF, Na 2 CO 3 and Na 3 PO 4, and only H 2 SO 4 (conc) react with KNO 3 (tv).

Answer: 3).

Methods for obtaining acids are very diverse.

Anoxic acids receive:

• by dissolving the corresponding gases in water:

HCl (g) + H 2 O (g) → HCl (p-p)

H 2 S (g) + H 2 O (g) → H 2 S (solution)

• from salts by displacement by stronger or less volatile acids:

FeS + 2HCl \u003d FeCl 2 + H 2 S

KCl (tv) + H 2 SO 4 (conc) = KHSO 4 + HCl

Na 2 SO 3 + H 2 SO 4 Na 2 SO 4 + H 2 SO 3

oxygenated acids receive:

• by dissolving the corresponding acid oxides in water, while the oxidation state of the acid-forming element in the oxide and acid remains the same (NO 2 is an exception):

N 2 O 5 + H 2 O \u003d 2HNO 3

SO 3 + H 2 O \u003d H 2 SO 4

P 2 O 5 + 3H 2 O 2H 3 PO 4

• oxidation of non-metals with oxidizing acids:

S + 6HNO 3 (conc) = H 2 SO 4 + 6NO 2 + 2H 2 O

• by displacing a strong acid from a salt of another strong acid (if a precipitate forms that is insoluble in the resulting acids):

Ba (NO 3) 2 + H 2 SO 4 (razb) \u003d BaSO 4 ↓ + 2HNO 3

AgNO 3 + HCl = AgCl↓ + HNO 3

• displacement of a volatile acid from its salts by a less volatile acid.

For this purpose, non-volatile thermally stable concentrated sulfuric acid is most often used:

NaNO 3 (tv) + H 2 SO 4 (conc) NaHSO 4 + HNO 3

KClO 4 (tv) + H 2 SO 4 (conc) KHSO 4 + HClO 4

• by displacing a weaker acid from its salts with a stronger acid:

Ca 3 (PO 4) 2 + 3H 2 SO 4 = 3CaSO 4 ↓ + 2H 3 PO 4

NaNO 2 + HCl = NaCl + HNO 2

K 2 SiO 3 + 2HBr = 2KBr + H 2 SiO 3 ↓

Classification of inorganic substances with examples of compounds

Let us now analyze the classification scheme presented above in more detail.

As we can see, first of all, all inorganic substances are divided into simple and complex:

simple substances substances that are formed by atoms of only one chemical element are called. For example, simple substances are hydrogen H 2 , oxygen O 2 , iron Fe, carbon C, etc.

Among simple substances, there are metals, nonmetals and noble gases:

Metals are formed by chemical elements located below the boron-astat diagonal, as well as by all elements that are in side groups.

noble gases formed by chemical elements of group VIIIA.

non-metals formed respectively by chemical elements located above the boron-astat diagonal, with the exception of all elements of secondary subgroups and noble gases located in group VIIIA:

The names of simple substances most often coincide with the names of the chemical elements whose atoms they are formed. However, for many chemical elements, the phenomenon of allotropy is widespread. Allotropy is the phenomenon when one chemical element is able to form several simple substances. For example, in the case of the chemical element oxygen, the existence of molecular compounds with the formulas O 2 and O 3 is possible. The first substance is usually called oxygen in the same way as the chemical element whose atoms it is formed, and the second substance (O 3) is usually called ozone. The simple substance carbon can mean any of its allotropic modifications, for example, diamond, graphite or fullerenes. The simple substance phosphorus can be understood as its allotropic modifications, such as white phosphorus, red phosphorus, black phosphorus.

Complex Substances

complex substances Substances made up of atoms of two or more elements are called.

So, for example, complex substances are ammonia NH 3, sulfuric acid H 2 SO 4, slaked lime Ca (OH) 2 and countless others.

Among complex inorganic substances, 5 main classes are distinguished, namely oxides, bases, amphoteric hydroxides, acids and salts:

oxides - complex substances formed by two chemical elements, one of which is oxygen in the -2 oxidation state.

The general formula for oxides can be written as E x O y, where E is the symbol of a chemical element.

Nomenclature of oxides

The name of the oxide of a chemical element is based on the principle:

For example:

Fe 2 O 3 - iron oxide (III); CuO, copper(II) oxide; N 2 O 5 - nitric oxide (V)

Often you can find information that the valency of the element is indicated in brackets, but this is not the case. So, for example, the oxidation state of nitrogen N 2 O 5 is +5, and the valency, oddly enough, is four.

If a chemical element has a single positive oxidation state in compounds, then the oxidation state is not indicated. For example:

Na 2 O - sodium oxide; H 2 O - hydrogen oxide; ZnO is zinc oxide.

Classification of oxides

Oxides, according to their ability to form salts when interacting with acids or bases, are divided, respectively, into salt-forming and non-salt-forming.

There are few non-salt-forming oxides, all of them are formed by non-metals in the oxidation state +1 and +2. The list of non-salt-forming oxides should be remembered: CO, SiO, N 2 O, NO.

Salt-forming oxides, in turn, are divided into main, acidic and amphoteric.

Basic oxides called such oxides, which, when interacting with acids (or acid oxides), form salts. The main oxides include metal oxides in the oxidation state +1 and +2, with the exception of oxides of BeO, ZnO, SnO, PbO.

Acid oxides called such oxides, which, when interacting with bases (or basic oxides), form salts. Acid oxides are almost all oxides of non-metals with the exception of non-salt-forming CO, NO, N 2 O, SiO, as well as all metal oxides in high oxidation states (+5, +6 and +7).

amphoteric oxides called oxides, which can react with both acids and bases, and as a result of these reactions form salts. Such oxides exhibit a dual acid-base nature, that is, they can exhibit the properties of both acidic and basic oxides. Amphoteric oxides include metal oxides in oxidation states +3, +4, and, as exceptions, oxides of BeO, ZnO, SnO, PbO.

Some metals can form all three types of salt-forming oxides. For example, chromium forms basic oxide CrO, amphoteric oxide Cr 2 O 3 and acid oxide CrO 3 .

As can be seen, the acid-base properties of metal oxides directly depend on the degree of oxidation of the metal in the oxide: the higher the degree of oxidation, the more pronounced the acidic properties.

Foundations

Foundations - compounds with a formula of the form Me (OH) x, where x most often equal to 1 or 2.

Base classification

Bases are classified according to the number of hydroxo groups in one structural unit.

Bases with one hydroxo group, i.e. type MeOH, called single acid bases with two hydroxo groups, i.e. type Me(OH) 2 , respectively, diacid etc.

Also, the bases are divided into soluble (alkali) and insoluble.

Alkalis include exclusively hydroxides of alkali and alkaline earth metals, as well as thallium hydroxide TlOH.

Base nomenclature

The name of the foundation is built according to the following principle:

For example:

Fe (OH) 2 - iron (II) hydroxide,

Cu (OH) 2 - copper (II) hydroxide.

In cases where the metal in complex substances has a constant oxidation state, it is not required to indicate it. For example:

NaOH - sodium hydroxide,

Ca (OH) 2 - calcium hydroxide, etc.

acids

acids - complex substances, the molecules of which contain hydrogen atoms that can be replaced by a metal.

The general formula of acids can be written as H x A, where H are hydrogen atoms that can be replaced by a metal, and A is an acid residue.

For example, acids include compounds such as H 2 SO 4 , HCl, HNO 3 , HNO 2 , etc.

Acid classification

According to the number of hydrogen atoms that can be replaced by a metal, acids are divided into:

- about monobasic acids: HF, HCl, HBr, HI, HNO 3 ;

- d acetic acids: H 2 SO 4 , H 2 SO 3 , H 2 CO 3 ;

- t rebasic acids: H 3 PO 4 , H 3 BO 3 .

It should be noted that the number of hydrogen atoms in the case of organic acids most often does not reflect their basicity. For example, acetic acid with the formula CH 3 COOH, despite the presence of 4 hydrogen atoms in the molecule, is not four-, but monobasic. The basicity of organic acids is determined by the number of carboxyl groups (-COOH) in the molecule.

Also, according to the presence of oxygen in acid molecules, they are divided into anoxic (HF, HCl, HBr, etc.) and oxygen-containing (H 2 SO 4, HNO 3, H 3 PO 4, etc.). Oxygenated acids are also called oxo acids.

You can read more about the classification of acids.

Nomenclature of acids and acid residues

The following list of names and formulas of acids and acid residues should be learned.

In some cases, a number of the following rules can make memorization easier.

As can be seen from the table above, the construction of the systematic names of anoxic acids is as follows:

For example:

HF, hydrofluoric acid;

HCl, hydrochloric acid;

H 2 S - hydrosulfide acid.

The names of the acid residues of oxygen-free acids are built according to the principle:

For example, Cl - - chloride, Br - - bromide.

The names of oxygen-containing acids are obtained by adding various suffixes and endings to the name of the acid-forming element. For example, if the acid-forming element in an oxygen-containing acid has the highest oxidation state, then the name of such an acid is constructed as follows:

For example, sulfuric acid H 2 S +6 O 4, chromic acid H 2 Cr +6 O 4.

All oxygen-containing acids can also be classified as acidic hydroxides, since hydroxo groups (OH) are found in their molecules. For example, this can be seen from the following graphical formulas of some oxygen-containing acids:

Thus, sulfuric acid may otherwise be called sulfur (VI) hydroxide, nitric acid - nitrogen (V) hydroxide, phosphoric acid - phosphorus (V) hydroxide, etc. The number in brackets characterizes the degree of oxidation of the acid-forming element. Such a variant of the names of oxygen-containing acids may seem extremely unusual to many, however, occasionally such names can be found in real KIMs of the Unified State Examination in chemistry in assignments for the classification of inorganic substances.

Amphoteric hydroxides

Amphoteric hydroxides - metal hydroxides exhibiting a dual nature, i.e. able to exhibit both the properties of acids and the properties of bases.

Amphoteric are metal hydroxides in oxidation states +3 and +4 (as well as oxides).

Also, compounds Be (OH) 2, Zn (OH) 2, Sn (OH) 2 and Pb (OH) 2 are included as exceptions to amphoteric hydroxides, despite the degree of oxidation of the metal in them +2.

For amphoteric hydroxides of tri- and tetravalent metals, the existence of ortho- and meta-forms is possible, differing from each other by one water molecule. For example, aluminum (III) hydroxide can exist in the ortho form of Al(OH) 3 or the meta form of AlO(OH) (metahydroxide).

Since, as already mentioned, amphoteric hydroxides exhibit both the properties of acids and the properties of bases, their formula and name can also be written differently: either as a base or as an acid. For example:

salt

So, for example, salts include compounds such as KCl, Ca(NO 3) 2, NaHCO 3, etc.

The above definition describes the composition of most salts, however, there are salts that do not fall under it. For example, instead of metal cations, the salt may contain ammonium cations or its organic derivatives. Those. salts include compounds such as, for example, (NH 4) 2 SO 4 (ammonium sulfate), + Cl - (methylammonium chloride), etc.

Salt classification

On the other hand, salts can be considered as products of substitution of hydrogen cations H + in an acid for other cations, or as products of substitution of hydroxide ions in bases (or amphoteric hydroxides) for other anions.

With complete substitution, the so-called medium or normal salt. For example, with the complete replacement of hydrogen cations in sulfuric acid with sodium cations, an average (normal) salt Na 2 SO 4 is formed, and with the complete replacement of hydroxide ions in the Ca (OH) 2 base with acid residues, nitrate ions form an average (normal) salt Ca(NO3)2.

Salts obtained by incomplete replacement of hydrogen cations in a dibasic (or more) acid with metal cations are called acid salts. So, with incomplete replacement of hydrogen cations in sulfuric acid by sodium cations, an acid salt NaHSO 4 is formed.

Salts that are formed by incomplete substitution of hydroxide ions in two-acid (or more) bases are called basic about salts. For example, with incomplete replacement of hydroxide ions in the Ca (OH) 2 base with nitrate ions, a basic about clear salt Ca(OH)NO 3 .

Salts consisting of cations of two different metals and anions of acid residues of only one acid are called double salts. So, for example, double salts are KNaCO 3 , KMgCl 3 , etc.

If the salt is formed by one type of cation and two types of acid residues, such salts are called mixed. For example, mixed salts are the compounds Ca(OCl)Cl, CuBrCl, etc.

There are salts that do not fall under the definition of salts as products of substitution of hydrogen cations in acids for metal cations or products of substitution of hydroxide ions in bases for anions of acid residues. These are complex salts. So, for example, complex salts are sodium tetrahydroxozincate and tetrahydroxoaluminate with the formulas Na 2 and Na, respectively. Recognize complex salts, among others, most often by the presence of square brackets in the formula. However, it must be understood that in order for a substance to be classified as a salt, its composition must include any cations, except for (or instead of) H +, and from the anions there must be any anions in addition to (or instead of) OH -. For example, the compound H 2 does not belong to the class of complex salts, since only hydrogen cations H + are present in solution during its dissociation from cations. According to the type of dissociation, this substance should rather be classified as an oxygen-free complex acid. Similarly, the OH compound does not belong to the salts, because this compound consists of cations + and hydroxide ions OH -, i.e. it should be considered a complex basis.

Salt nomenclature

Nomenclature of medium and acid salts

The name of medium and acid salts is based on the principle:

If the degree of oxidation of the metal in complex substances is constant, then it is not indicated.

The names of the acid residues were given above when considering the nomenclature of acids.

For example,

Na 2 SO 4 - sodium sulfate;

NaHSO 4 - sodium hydrosulfate;

CaCO 3 - calcium carbonate;

Ca (HCO 3) 2 - calcium bicarbonate, etc.

Nomenclature of basic salts

The names of the main salts are built according to the principle:

For example:

(CuOH) 2 CO 3 - copper (II) hydroxocarbonate;

Fe (OH) 2 NO 3 - iron (III) dihydroxonitrate.

Nomenclature of complex salts

The nomenclature of complex compounds is much more complicated, and for passing the exam You don't need to know much about the nomenclature of complex salts.

One should be able to name complex salts obtained by the interaction of alkali solutions with amphoteric hydroxides. For example:

*The same colors in the formula and the name indicate the corresponding elements of the formula and the name.

Trivial names of inorganic substances

Trivial names are understood as the names of substances that are not related, or weakly related to their composition and structure. Trivial names are due, as a rule, either historical reasons either physical or chemical properties connection data.

List of trivial names of inorganic substances that you need to know:

Na 3	cryolite
SiO2	quartz, silica
FeS 2	pyrite, iron pyrite
CaSO 4 ∙2H 2 O	gypsum
CaC2	calcium carbide
Al 4 C 3	aluminum carbide
KOH	caustic potash
NaOH	caustic soda, caustic soda
H2O2	hydrogen peroxide
CuSO 4 ∙5H 2 O	blue vitriol
NH4Cl	ammonia
CaCO3	chalk, marble, limestone
N2O	laughing gas
NO 2	brown gas
NaHCO3	food (drinking) soda
Fe 3 O 4	iron oxide
NH 3 ∙H 2 O (NH 4 OH)	ammonia
CO	carbon monoxide
CO2	carbon dioxide
SiC	carborundum (silicon carbide)
PH 3	phosphine
NH3	ammonia
KClO 3	berthollet salt (potassium chlorate)
(CuOH) 2 CO 3	malachite
CaO	quicklime
Ca(OH)2	slaked lime
transparent aqueous solution of Ca(OH) 2	lime water
a suspension of solid Ca (OH) 2 in its aqueous solution	milk of lime
K2CO3	potash
Na2CO3	soda ash
Na 2 CO 3 ∙10H 2 O	crystal soda
MgO	magnesia

acids- complex substances consisting of one or more hydrogen atoms that can be replaced by metal atoms, and acid residues.

Acid classification

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

n= 1 single base

n= 2 dibasic

n= 3 tribasic

2. By composition:

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

Acid (H n A)	Acid residue (A)	Corresponding acid oxide
H 2 SO 4 sulfuric	SO 4 (II) sulfate	SO 3 sulfur oxide (VI)
HNO 3 nitric	NO 3 (I) nitrate	N 2 O 5 nitric oxide (V)
HMnO 4 manganese	MnO 4 (I) permanganate	Mn2O7 manganese oxide ( VII)
H 2 SO 3 sulfurous	SO 3 (II) sulfite	SO 2 sulfur oxide (IV)
H 3 PO 4 orthophosphoric	PO 4 (III) orthophosphate	P 2 O 5 phosphorus oxide (V)
HNO 2 nitrogenous	NO 2 (I) nitrite	N 2 O 3 nitric oxide (III)
H 2 CO 3 coal	CO 3 (II) carbonate	CO2 carbon monoxide ( IV)
H 2 SiO 3 silicon	SiO 3 (II) silicate	SiO 2 silicon oxide (IV)
HClO hypochlorous	СlO(I) hypochlorite	C l 2 O chlorine oxide (I)
HClO 2 chloride	Сlo 2 (I) chlorite	C l 2 O 3 chlorine oxide (III)
HClO 3 chloric	СlO 3 (I) chlorate	C l 2 O 5 chlorine oxide (V)
HClO 4 chloride	СlO 4 (I) perchlorate	С l 2 O 7 chlorine oxide (VII)

b) Table of anoxic acids

Acid (N n A)	Acid residue (A)
HCl hydrochloric, hydrochloric	Cl(I) chloride
H 2 S hydrogen sulfide	S(II) sulfide
HBr hydrobromic	Br(I) bromide
HI hydroiodic	I(I) iodide
HF hydrofluoric, hydrofluoric	F(I) fluoride

Physical properties of acids

Many acids, such as sulfuric, nitric, 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 H2SiO3 . Acid solutions have a sour taste. So, for example, many fruits give a sour taste to the acids they contain. Hence the names of acids: citric, malic, etc.

Methods for obtaining acids

anoxic	oxygen-containing
HCl, HBr, HI, HF, H2S	HNO 3 , H 2 SO 4 and others
RECEIVING
1. Direct interaction of non-metals H 2 + Cl 2 \u003d 2 HCl	1. Acid oxide + water = acid SO 3 + H 2 O \u003d H 2 SO 4
2. Exchange reaction between salt and less volatile acid 2 NaCl (tv.) + H 2 SO 4 (conc.) \u003d Na 2 SO 4 + 2HCl

Chemical properties of acids

1. Change the color of the indicators

Name of the indicator	Neutral environment	acid environment
Litmus	Violet	Red
Phenolphthalein	Colorless	Colorless
Methyl orange	Orange	Red
Universal indicator paper	orange	Red

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 \u003d SALT + H 2 (p. substitution)

Zn + 2 HCl \u003d ZnCl 2 + H 2

3. With basic (amphoteric) oxides – metal oxides

Video "Interaction of metal oxides with acids"

Me x O y + ACID \u003d SALT + H 2 O (p. exchange)

4. React with bases – neutralization reaction

ACID + BASE = SALT + H 2 O (p. exchange)

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

5. React with salts of weak, volatile acids - if an acid is formed that precipitates or a gas is released:

2 NaCl (tv.) + H 2 SO 4 (conc.) \u003d 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 PO 4 )

ACID = ACID OXIDE + WATER (r. decomposition)

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

H 2 CO 3 ↔ H 2 O + CO 2

H 2 SO 3 ↔ H 2 O + SO 2

Hydrosulphuric acid in products released as a gas:

CaS + 2HCl \u003d H 2 S+ CaCl2

TASKS FOR REINFORCEMENT

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-

main

two-core

tri-basic

No. 2. Write reaction equations:

Ca+HCl

Na + H 2 SO 4

Al + H 2 S

Ca + H 3 PO 4
Name the reaction products.

No. 3. Make the reaction equations, name the products:

Na 2 O + H 2 CO 3

ZnO + HCl

CaO + HNO3

Fe 2 O 3 + H 2 SO 4

No. 4. Make up the reaction equations for the interaction 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

H 2 SO 4 + K 2 CO 3

HNO 3 + CaCO 3

Name the reaction products.

SIMULATORS

Trainer number 1. "Formulas and names of acids"

Trainer number 2. "Correspondence: acid formula - oxide formula"

Safety Precautions - First Aid for Skin Contact with Acids

Safety -

Substances that dissociate in solutions to form hydrogen ions are called.

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

By strengthacids are divided into strong and weak. The most important strong acids are nitric HNO 3 , sulfuric H 2 SO 4 , and hydrochloric HCl .

By the presence of oxygen distinguish oxygen-containing acids ( HNO3, H3PO4 etc.) and anoxic 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, H 2 S 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". At the same time, 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, HClO 4 - perchloric acid, H 3 AsO 4 - arsenic acid. With a decrease in the degree of oxidation of the acid-forming element, the endings change in the following sequence: “oval” ( HClO 3 - chloric acid), "pure" ( HClO 2 - chlorous acid), "wobbly" ( H O Cl - hypochlorous acid). If the element forms acids, being in only two oxidation states, then the name of the acid corresponding to the lowest oxidation state of the element receives the ending "pure" ( HNO3 - Nitric acid, HNO 2 - nitrous acid).

Table - The most important acids and their salts

Acid		Names of the corresponding normal salts
Name	Formula
Nitrogen	HNO3	Nitrates
nitrogenous	HNO 2	Nitrites
Boric (orthoboric)	H3BO3	Borates (orthoborates)
Hydrobromic		Bromides
Hydroiodine		iodides
Silicon	H2SiO3	silicates
manganese	HMnO 4	Permanganates
Metaphosphoric	HPO 3	Metaphosphates
Arsenic	H 3 AsO 4	Arsenates
Arsenic	H 3 AsO 3	Arsenites
orthophosphoric	H3PO4	Orthophosphates (phosphates)
Diphosphoric (pyrophosphoric)	H4P2O7	Diphosphates (pyrophosphates)
dichrome	H2Cr2O7	Dichromates
sulfuric	H2SO4	sulfates
sulphurous	H2SO3	Sulfites
Coal	H2CO3	Carbonates
Phosphorous	H3PO3	Phosphites
Hydrofluoric (hydrofluoric)		Fluorides
Hydrochloric (hydrochloric)		chlorides
Chloric	HClO 4	Perchlorates
Chlorine	HClO 3	Chlorates
hypochlorous	HClO	Hypochlorites
Chrome	H2CrO4	Chromates
Hydrogen cyanide (hydrocyanic)		cyanides

Obtaining acids

1. Anoxic 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 \u003d H 2 SO 4,

CO 2 + H 2 O \u003d H 2 CO 3,

P 2 O 5 + H 2 O \u003d 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 \u003d BaSO 4 + 2HBr,

CuSO 4 + H 2 S \u003d H 2 SO 4 + CuS,

CaCO 3 + 2HBr \u003d CaBr 2 + CO 2 + H 2 O.

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

H 2 O 2 + SO 2 \u003d H 2 SO 4,

3P + 5HNO 3 + 2H 2 O = 3H 3 PO 4 + 5NO.

Chemical properties of acids

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

H 2 SO 4 + 2NaOH \u003d Na 2 SO 4 + 2H 2 O,

2HNO 3 + FeO \u003d Fe (NO 3) 2 + H 2 O,

2 HCl + ZnO \u003d ZnCl 2 + H 2 O.

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

Zn + 2HCl \u003d ZnCl 2 + H 2,

2Al + 6HCl \u003d 2AlCl 3 + 3H 2.

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

H 2 SO 4 + BaCl 2 = BaSO 4 ↓ + 2HCl,

2HCl + Na 2 CO 3 \u003d 2NaCl + H 2 O + CO 2,

2KHCO 3 + H 2 SO 4 \u003d K 2 SO 4 + 2SO 2+ 2H2O.

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

Na 2 S + H 3 PO 4 \u003d 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 P2O5):

H 2 SO 4 \u003d H 2 O + SO 3,

H 2 SiO 3 \u003d H 2 O + SiO 2.

M.V. Andryukhova, L.N. Borodin

acids- electrolytes, during the 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 easily mobile, colorless liquids with a characteristic pungent odor; acids with 4-9 carbon atoms are oily liquids with an unpleasant odor, and acids with a large number of carbon atoms are solids that are insoluble in water.

Chemical formulas of acids

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) \u003d 1 amu, Ar (Cl) \u003d 35.5 a.m.). m.u., Ar(P) = 31 a.m.u., Ar(O) = 16 a.m.u., Ar(S) = 32 a.m.u., Ar(C) = 12 a.u.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) \u003d 2 × 1 + 32 + 4 × 16 \u003d 2 + 32 + 64 \u003d 98.

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

Mr(H 3 PO 4) \u003d 3 × 1 + 31 + 4 × 16 \u003d 3 + 31 + 64 \u003d 98.

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

Mr(CH 3 COOH) = 3x12 + 4x1 + 2x16 = 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) = 7x12 + 6x1 + 2x16 = 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

Exercise	With the complete combustion of 6 g of organic matter, 8.8 g of carbon monoxide (IV) and 3.6 g of water were formed. Determine the molecular formula of the burned substance if its molar mass is known to be 180 g/mol.
Decision	Let's make a scheme of the combustion reaction organic compound denoting the number of carbon, hydrogen and oxygen atoms as "x", "y" and "z", respectively: C x H y O z + O z →CO 2 + H 2 O. Let us determine the masses of the elements that make up this substance. The values ​​of relative atomic masses taken from the Periodic Table of D.I. Mendeleev, rounded up to integers: Ar(C) = 12 a.m.u., Ar(H) = 1 a.m.u., Ar(O) = 16 a.m.u. m(C) = n(C)×M(C) = n(CO 2)×M(C) = ×M(C); m(H) = n(H)×M(H) = 2×n(H 2 O)×M(H) = ×M(H); Calculate the molar masses of carbon dioxide and water. As is known, the molar mass of a molecule is equal to the sum of the relative atomic masses of the atoms that make up the molecule (M = Mr): M(CO 2) \u003d Ar (C) + 2 × Ar (O) \u003d 12+ 2 × 16 \u003d 12 + 32 \u003d 44 g / mol; M(H 2 O) \u003d 2 × Ar (H) + Ar (O) \u003d 2 × 1 + 16 \u003d 2 + 16 \u003d 18 g / mol. m(C)=×12=2.4 g; m (H) \u003d 2 × 3.6 / 18 × 1 \u003d 0.4 g. m(O) \u003d m (C x H y O z) - m (C) - m (H) \u003d 6 - 2.4 - 0.4 \u003d 3.2 g. Let's define the chemical formula of the compound: x:y:z = m(C)/Ar(C) : m(H)/Ar(H) : m(O)/Ar(O); x:y:z= 2.4/12:0.4/1:3.2/16; x:y:z= 0.2: 0.4: 0.2 = 1: 2: 1. Means the simplest formula compounds CH 2 O and a molar mass of 30 g / mol. To find the true formula of an organic compound, we find the ratio of the true and obtained molar masses: M substance / M (CH 2 O) \u003d 180 / 30 \u003d 6. This means that the indices of carbon, hydrogen and oxygen atoms should be 6 times higher, i.e. the formula of the substance will look like C 6 H 12 O 6. Is it glucose or fructose.
Answer	C6H12O6

EXAMPLE 2

Exercise	Derive the simplest formula of a compound in which the mass fraction of phosphorus is 43.66%, and the mass fraction of oxygen is 56.34%.
Decision	The mass fraction of element X in a molecule of composition HX is calculated from following formula: ω (X) = n × Ar (X) / M (HX) × 100%. Let us denote the number of phosphorus atoms in the molecule as "x", and the number of oxygen atoms as "y" Let us find the corresponding relative atomic masses of the elements phosphorus and oxygen (the values ​​of the relative atomic masses taken from the Periodic Table of D.I. Mendeleev will be rounded up to whole numbers). Ar(P) = 31; Ar(O) = 16. We divide the percentage of elements by the corresponding relative atomic masses. Thus, we will find the relationship between the number of atoms in the molecule of the compound: x:y = ω(P)/Ar(P) : ω(O)/Ar(O); x:y = 43.66/31: 56.34/16; x:y: = 1.4: 3.5 = 1: 2.5 = 2: 5. This means that the simplest formula for the combination of phosphorus and oxygen has the form P 2 O 5. It is phosphorus(V) oxide.
Answer	P2O5