Method of formation of names of acids. Inorganic acids

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:

Acid (H n A)	Acid residue (A)	Corresponding acid oxide
H 2 SO 4 sulfuric	SO 4 (II) sulfate	SO3 sulfur oxide (VI)
HNO 3 nitrogen	NO3(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	SO2 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(IV) oxide
HClO hypochlorous	ClO(I) hypochlorite	C l 2 O chlorine oxide (I)
HClO 2 chloride	ClO 2 (I) chlorite	C l 2 O 3 chlorine oxide (III)
HClO 3 chlorate	ClO 3 (I) chlorate	C l 2 O 5 chlorine oxide (V)
HClO 4 chlorine	ClO 4 (I) perchlorate	C l 2 O 7 chlorine oxide (VII)

b) Table of oxygen-free acids

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

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

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

Chemical properties of acids

1. Change the color of the indicators

Indicator name	Neutral environment	Acidic 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 = 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-

relatives

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 -

Complex substances consisting of hydrogen atoms and an acid residue are called mineral or inorganic acids. The acid residue is oxides and non-metals combined with hydrogen. The main property of acids is the ability to form salts.

Classification

The basic formula of mineral acids is H n Ac, where Ac is the acid residue. Depending on the composition of the acid residue, two types of acids are distinguished:

• oxygen containing oxygen;
• oxygen-free, consisting only of hydrogen and non-metal.

The main list of inorganic acids according to type is presented in the table.

Type	Name	Formula
Oxygen
	Nitrogenous
	Dichrome
	Iodineous
	Silicon - metasilicon and orthosilicon	H 2 SiO 3 and H 4 SiO 4
	Manganese
	Manganese
	Metaphosphoric
	Arsenic
	Orthophosphoric
	Sulphurous
	Thiosulfur
	Tetrathionic
	Coal
	Phosphorous
	Phosphorous
	Chlorous
	Chloride
	Hypochlorous
	Chrome
	Cyan
Oxygen-free	Hydrofluoric (fluoric)
	Hydrochloric (salt)
	Hydrobromic
	Hydroiodic
	Hydrogen sulfide
	Hydrogen cyanide

In addition, according to their properties, acids are classified according to the following criteria:

• solubility: soluble (HNO 3, HCl) and insoluble (H 2 SiO 3);
• volatility: volatile (H 2 S, HCl) and non-volatile (H 2 SO 4, H 3 PO 4);
• degree of dissociation: strong (HNO 3) and weak (H 2 CO 3).

Rice. 1. Acid classification scheme.

Traditional and trivial names are used to designate mineral acids. Traditional names correspond to the name of the element that forms the acid with the addition of the morphemes -naya, -ovaya, as well as -istaya, -novataya, -novataya to indicate the degree of oxidation.

Receipt

The main methods for producing acids are presented in the table.

Properties

Most acids are liquids with a sour taste. Tungstic, chromic, boric and several other acids are in a solid state under normal conditions. Some acids (H 2 CO 3, H 2 SO 3, HClO) exist only in the form of an aqueous solution and are classified as weak acids.

Rice. 2. Chromic acid.

Acids are active substances that react:

• with metals:

  Ca + 2HCl = CaCl 2 + H 2;

• with oxides:

  CaO + 2HCl = CaCl 2 + H 2 O;

• with base:

  H 2 SO 4 + 2KOH = K 2 SO 4 + 2H 2 O;

• with salts:

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

All reactions are accompanied by the formation of salts.

A qualitative reaction with a change in the color of the indicator is possible:

• litmus turns red;
• methyl orange - to pink;
• phenolphthalein does not change.

Rice. 3. Colors of indicators when acid reacts.

The chemical properties of mineral acids are determined by their ability to dissociate in water to form hydrogen cations and anions of hydrogen residues. Acids that react irreversibly with water (dissociate completely) are called strong. These include chlorine, nitrogen, sulfur and hydrogen chloride.

What have we learned?

Inorganic acids are formed by hydrogen and an acid residue, which is a non-metal atom or an oxide. Depending on the nature of the acid residue, acids are classified into oxygen-free and oxygen-containing. All acids have a sour taste and are capable of dissociating in an aqueous environment (breaking down into cations and anions). Acids are obtained from simple substances, oxides, and salts. When interacting with metals, oxides, bases, and salts, acids form salts.

Test on the topic

Evaluation of the report

Average rating: 4.4. Total ratings received: 120.

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 in the form of hydrogen cations H + upon dissociation, 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 that such dissociation is virtually irreversible. 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 the chemical element included in 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.

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 degree of oxidation of the acid-forming element, the endings change in the following sequence: “ovate” ( HClO3 - perchloric acid), “solid” ( HClO2 - chlorous acid), “ovate” ( H O Cl - hypochlorous acid). If an element forms acids while being in only two oxidation states, then the name of the acid corresponding to the lowest oxidation state of the element receives the ending “empty” ( HNO3 - nitric acid, HNO2 - nitrous acid).

Table - The most important acids and their salts

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 P 2 O 5 ):

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

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

M.V. Andryukhova, L.N. Borodina