1. Salts are electrolytes.

In aqueous solutions, salts dissociate into positively charged metal ions (cations) and negatively charged ions (anions) of acidic residues.

For example, when sodium chloride crystals are dissolved in water, positively charged sodium ions and negatively charged chloride ions, from which the crystal lattice of this substance is formed, go into solution:

NaCl → NaCl − .

During the electrolytic dissociation of aluminum sulfate, positively charged aluminum ions and negatively charged sulfate ions are formed:

Al 2 SO 4 3 → 2 Al 3 3 SO 4 2 − .

2. Salts can interact with metals.

During a substitution reaction occurring in an aqueous solution, a chemically more active metal displaces a less active one.

For example If a piece of iron is placed in a solution of copper sulfate, it becomes covered with a red-brown copper precipitate. The solution gradually changes color from blue to pale green as an iron salt is formed (\(II\)):

Fe Cu SO 4 → Fe SO 4 Cu ↓ .

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When copper chloride (\(II\)) reacts with aluminum, aluminum chloride and copper are formed:
2 Al 3Cu Cl 2 → 2Al Cl 3 3 Cu ↓ .

3. Salts can interact with acids.

An exchange reaction occurs during which a chemically more active acid displaces a less active one.

For example, when a solution of barium chloride interacts with sulfuric acid, a precipitate of barium sulfate is formed, and hydrochloric acid remains in the solution:
BaCl 2 H 2 SO 4 → Ba SO 4 ↓ 2 HCl.

When calcium carbonate reacts with hydrochloric acid, calcium chloride and carbonic acid are formed, which immediately decomposes into carbon dioxide and water:

Ca CO 3 2 HCl → CaCl 2 H 2 O CO 2 H 2 CO 3 .

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4. Water-soluble salts can react with alkalis.

An exchange reaction is possible if, as a result, at least one of the products is practically insoluble (precipitates).

For example, when nickel nitrate (\(II\)) reacts with sodium hydroxide, sodium nitrate and practically insoluble nickel hydroxide (\(II\)) are formed:
Ni NO 3 2 2 NaOH → Ni OH 2 ↓ 2Na NO 3.

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When sodium carbonate (soda) reacts with calcium hydroxide (slaked lime), sodium hydroxide and practically insoluble calcium carbonate are formed:
Na 2 CO 3 Ca OH 2 → 2NaOH Ca CO 3 ↓ .

5. Water-soluble salts can enter into an exchange reaction with other water-soluble salts if the result is the formation of at least one practically insoluble substance.

For example, when sodium sulfide reacts with silver nitrate, sodium nitrate and practically insoluble silver sulfide are formed:
Na 2 S 2Ag NO 3 → Na NO 3 Ag 2 S ↓.

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When barium nitrate reacts with potassium sulfate, potassium nitrate and practically insoluble barium sulfate are formed:
Ba NO 3 2 K 2 SO 4 → 2 KNO 3 BaSO 4 ↓ .

6. Some salts decompose when heated.

Moreover, the chemical reactions that occur in this case can be divided into two groups:

• reactions during which elements do not change their oxidation state,
• redox reactions.

A. Reactions of decomposition of salts that occur without changing the oxidation state of elements.

As examples of such chemical reactions, let us consider how the decomposition of carbonates occurs.

When heated strongly, calcium carbonate (chalk, limestone, marble) decomposes, forming calcium oxide (burnt lime) and carbon dioxide:
CaCO 3 t ° CaO CO 2 .

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Sodium bicarbonate ( baking soda) with slight heating decomposes into sodium carbonate (soda), water and carbon dioxide:
2 NaHCO 3 t ° Na 2 CO 3 H 2 O CO 2 .

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Crystalline salt hydrates lose water when heated. For example, copper sulfate pentahydrate (\(II\)) (copper sulfate), gradually losing water, turns into anhydrous copper sulfate (\(II\)):
CuSO 4 ⋅ 5 H 2 O → t ° Cu SO 4 5 H 2 O.

Under normal conditions, the resulting anhydrous copper sulfate can be converted into crystalline hydrate:
CuSO 4 5 H 2 O → Cu SO 4 ⋅ 5 H 2 O

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In order to answer the question of what salt is, you usually don’t have to think long. This is a chemical compound in Everyday life occurs quite often. There is no need to talk about ordinary table salt. Detailed internal structure salts and their compounds are studied in inorganic chemistry.

Definition of salt

A clear answer to the question of what salt is can be found in the works of M.V. Lomonosov. He assigned this name to fragile bodies that can dissolve in water and do not ignite when exposed to high temperatures or open fire. Later, the definition was derived not from their physical, but from the chemical properties of these substances.

School textbooks inorganic chemistry give a fairly clear concept of what salt is. This is the name given to the substitution products of a chemical reaction in which the hydrogen atoms of an acid in a compound are replaced by a metal. Examples of typical salt compounds: NaCL, MgSO 4 . It is easy to see that any of this entries can be divided into two halves: the left component of the formula will always contain the metal, and the right - the acid residue. The standard salt formula is as follows:

Me n m Acid residue m n .

Physical properties of salt

Chemistry, as an exact science, puts into the name of a substance all possible information about its composition and capabilities. Thus, all names of salts in the modern interpretation consist of two words: one part has the name of the metal component in the nominative case, the second contains a description of the acidic residue.

These compounds do not have a molecular structure, so under normal conditions they are solids. crystalline substances. Many salts have a crystal lattice. The crystals of these substances are refractory, so very high temperatures are required to melt them. For example, barium sulfide melts at a temperature of about 2200 o C.

Based on solubility, salts are divided into soluble, slightly soluble and insoluble. Examples of the former include sodium chloride and potassium nitrate. Slightly soluble include magnesium sulfite and lead chloride. Insoluble is calcium carbonate. Information on the solubility of a particular substance is contained in reference literature.

The product of the chemical reaction in question is usually odorless and has a variable taste. The assumption that all salts are salty is wrong. Only one element of this class has a pure salty taste - our old friend table salt. There are sweet beryllium salts, bitter magnesium salts, and tasteless salts, for example, calcium carbonate (common chalk).

Most of these substances are colorless, but among them there are some that have characteristic colors. For example, iron (II) sulfate has a characteristic green, potassium permanganate is purple, and potassium chromate crystals are bright yellow.

Salt classification

Chemistry separates all species inorganic salts on several basic features. Salts obtained by complete replacement of hydrogen in an acid are called normal or medium. For example, calcium sulfate.

A salt that is derived from an incomplete substitution reaction is called acidic or basic. An example of such formation is the reaction of potassium hydrogen sulfate:

The basic salt is obtained in a reaction in which the hydroxo group is not completely replaced by an acidic residue. Substances of this type can be formed by those metals whose valency is two or more. A typical formula for a salt of this group can be derived from the following reaction:

Normal, average and acidic chemical compounds form the classes of salts and are the standard classification of these compounds.

Double and mixed salt

An example of a mixed acid is the calcium salt of hydrochloric and hypochlorous acid: CaOCl 2.

Nomenclature

Salts formed by metals with variable valence, have an additional designation: after the formula, the valence is written in Roman numerals in parentheses. Thus, there is iron sulfate FeSO 4 (II) and Fe 2 (SO4) 3 (III). The name of a salt contains the prefix hydro- if it contains unsubstituted hydrogen atoms. For example, potassium hydrogen phosphate has the formula K 2 HPO 4 .

Properties of salts in electrolytes

The theory of electrolytic dissociation gives its own interpretation chemical properties. In light of this theory, salt can be defined as a weak electrolyte which, when dissolved, dissociates (breaks apart) in water. Thus, a salt solution can be represented as a complex of positive negative ions, and the first are not hydrogen atoms H +, and the second are not atoms of the hydroxyl group OH -. There are no ions that are present in all types of salt solutions, so any general properties they don't have. The lower the charges of the ions that form the salt solution, the better they dissociate, the better the electrical conductivity of such a liquid mixture.

Solutions of acid salts

Acidic salts in solution break down into complex negative ions, which are the acid residue, and simple anions, which are positively charged metal particles.

For example, the dissolution reaction of sodium bicarbonate leads to the decomposition of the salt into sodium ions and the remainder HCO 3 -.

Complete formula looks like this: NaHCO 3 = Na + + HCO 3 -, HCO 3 - = H + + CO 3 2-.

Solutions of basic salts

Dissociation of basic salts leads to the formation of acid anions and complex cations consisting of metals and hydroxyl groups. These complex cations, in turn, are also capable of breaking down during dissociation. Therefore, in any solution of a salt of the main group, OH - ions are present. For example, the dissociation of hydroxomagnesium chloride proceeds as follows:

Spread of salts

What is salt? This element is one of the most common chemical compounds. Everyone knows table salt, chalk (calcium carbonate) and so on. Among carbonate acid salts, the most common is calcium carbonate. It is a component of marble, limestone, and dolomite. Calcium carbonate is also the basis for the formation of pearls and corals. This chemical compound is an integral component for the formation of hard integument in insects and skeletons in chordates.

Table salt has been known to us since childhood. Doctors warn against its excessive use, but in moderation it is essential for vital processes in the body. And it is needed to maintain the correct blood composition and the production of gastric juice. Saline solutions, an integral part of injections and droppers, are nothing more than a solution of table salt.

Salts - organic and inorganic chemical substances complex composition. In chemical theory there is no strict and final definition of salts. They can be described as compounds:
- consisting of anions and cations;
— obtained as a result of the interaction of acids and bases;
- consisting of acidic residues and metal ions.

Acidic residues can be associated not with metal atoms, but with ammonium ions (NH 4) +, phosphonium (PH 4) +, hydronium (H 3 O) + and some others.

Types of salts

- Acid, medium, basic. If all the hydrogen protons in an acid are replaced by metal ions, then such salts are called medium salts, for example, NaCl. If hydrogen is only partially replaced, then such salts are acidic, for example. KHSO 4 and NaH 2 PO 4. If the hydroxyl groups (OH) of the base are not completely replaced by the acidic residue, then the salt is basic, for example. CuCl(OH), Al(OH)SO 4 .

- Simple, double, mixed. Simple salts consist of one metal and one acid residue, for example, K 2 SO 4. Double salts contain two metals, for example KAl(SO 4) 2. Mixed salts have two acidic residues, e.g. AgClBr.

— Organic and inorganic.
— Complex salts with a complex ion: K 2 , Cl 2 and others.
— Crystal hydrates and crystal solvates.
— Crystalline hydrates with molecules of water of crystallization. CaSO 4 *2H 2 O.
— Crystal solvates with solvent molecules. For example, LiCl in liquid ammonia NH 3 gives LiCl*5NH 3 solvate.
— Oxygen-containing and oxygen-free.
— Internal, otherwise called bipolar ions.

Properties

Most salts are solids with high temperature melting, non-conducting. Solubility in water is an important characteristic; on its basis, reagents are divided into water-soluble, slightly soluble and insoluble. Many salts dissolve in organic solvents.

Salts react:
— with more active metals;
- with acids, bases, and other salts, if the interaction produces substances that do not participate in further reactions, for example, gas, insoluble precipitate, water. They decompose when heated and hydrolyze in water.

In nature, salts are widely distributed in the form of minerals, brines, and salt deposits. They are also obtained from sea ​​water, mining ores.

Salts are necessary to the human body. Iron salts are needed to replenish hemoglobin, calcium - participate in the formation of the skeleton, magnesium - regulate the activity of the gastrointestinal tract.

Application of salts

Salts are actively used in production, everyday life, agriculture, medicine, food industry, chemical synthesis and analysis, in laboratory practice. Here are just a few areas of their application:

— Sodium, potassium, calcium and ammonium nitrates (saltpeter); calcium phosphate, Potassium chloride is a raw material for the production of fertilizers.
— Sodium chloride is necessary for the production of table salt; it is used in the chemical industry for the production of chlorine, soda, and caustic soda.
— Sodium hypochlorite is a popular bleach and water disinfectant.
— Salts of acetic acid (acetates) are used in the food industry as preservatives (potassium and calcium acetate); in medicine for the manufacture of drugs, in the cosmetics industry (sodium acetate), for many other purposes.
— Potassium-aluminum and potassium-chromium alums are in demand in medicine and the food industry; for dyeing fabrics, leather, furs.
— Many salts are used as fixatives for determining chemical composition substances, water quality, acidity level, etc.

Our store offers a wide range of salts, both organic and inorganic.

The foundations for dividing salts into separate groups were laid in the works French chemist and pharmacist G. Ruel(\(1703\)–\(1770\)) . It was he who in \(1754\) proposed dividing the salts known by that time into acidic, basic and medium (neutral). Currently, other groups of this extremely important class of compounds are being identified.

Medium salts

Medium salts are salts that contain a metal chemical element and an acidic residue.

Instead of a metal chemical element, ammonium salts contain a monovalent ammonium group NH 4 I.

Examples of medium salts:

Na I Cl I - sodium chloride;
Al 2 III SO 4 II 3 - aluminum sulfate;
NH I 4 NO 3 I - ammonium nitrate.

Acid salts

Salts are called acidic if they contain, in addition to a metal chemical element and an acidic residue, hydrogen atoms.

Pay attention!

When composing the formulas of acid salts, it should be borne in mind that the valence of the acid residue is numerically equal to the number of hydrogen atoms that were part of the acid molecule and replaced by the metal.

When compiling the name of such a compound, the prefix “” is added to the name of the salt. hydro", if the acid residue contains one hydrogen atom, and " dihydro"if the acid residue contains two hydrogen atoms.

Examples of acid salts:

Ca II HCO 3 I 2 - calcium bicarbonate;
Na 2 I HPO 4 II - sodium hydrogen phosphate;
Na I H 2 PO 4 I is sodium dihydrogen phosphate.

The simplest example of acidic salts is baking soda, i.e. sodium bicarbonate \(NaHCO_3\).

Basic salts

Basic salts are salts that contain, in addition to a metal chemical element and an acidic residue, hydroxyl groups.

Basic salts can be considered as a product of incomplete neutralization of a polyacid base.

Pay attention!

When composing the formulas of such substances, it should be borne in mind that the valency of the residue from the base is numerically equal to the number of hydroxo groups that have “left” the composition of the base.

When compiling the name of the main salt, the prefix “ hydroxo", if the remainder of the base contains one hydroxo group, and " dihydroxo", if the remainder of the base contains two hydroxo groups.

Examples of basic salts:

MgOH I Cl I - magnesium hydroxychloride;
Fe OH II NO 3 2 I - iron hydroxonitrate (\(III\));
Fe OH 2 I NO 3 I - iron dihydroxonitrate (\(III\)).

A well-known example of basic salts is plaque Green colour copper hydroxycarbonate (\(II\)) \((CuOH)_2CO_3\), formed over time on copper objects and objects made from copper alloys if they come into contact with moist air. The mineral malachite has the same composition.

Complex salts

Complex compounds are a diverse class of substances. The credit for creating a theory explaining their composition and structure belongs to the laureate Nobel Prize in chemistry \(1913\) to a Swiss scientist A. Werner (\(1866\)–\(1919\)). True, the term “complex compounds” was introduced in \(1889\) by another outstanding chemist, Nobel Prize laureate \(1909\). V. Ostwald (\(1853\)–\(1932\)).

The cation or anion of complex salts contains complexing element associated with so-called ligands. The number of ligands that the complexing agent attaches is called coordination number. For example, the coordination number of divalent copper, as well as beryllium and zinc, is \(4\). The coordination number of aluminum, iron, trivalent chromium is \(6\).

In the name of a complex compound, the number of ligands connected to the complexing agent is represented by Greek numerals: \(2\) - “ di", \(3\) - " three", \(4\) - " tetra", \(5\) - " penta", \(6\) - " hexa" Both electrically neutral molecules and ions can act as ligands.

The name of the complex anion begins with the composition of the inner sphere.

If anions act as ligands, the ending “ -O»:

\(–Cl\) - chloro-, \(–OH\) - hydroxo-, \(–CN\) - cyano-.

If the ligands are electrically neutral water molecules, the name " aqua", and if ammonia - the name " ammin».

Then the complexing agent is called using its Latin name and the ending “- at", after which, without a space, the degree of oxidation is indicated in Roman numerals in brackets (if the complexing agent can have several oxidation states).

After indicating the composition of the inner sphere, indicate the name of the cation of the outer sphere - the one that is outside the square brackets in the chemical formula of the substance.

Example:

K 2 Zn OH 4 - potassium tetrahydroxozincate,
K 3 Al OH 6 - potassium hexahydroxoaluminate,
K 4 Fe CN 6 - potassium hexacyanoferrate (\(II\)).

In school textbooks, the formulas for complex salts of more complex composition are, as a rule, simplified. For example, the formula of potassium tetrahydroxodiaquaaluminate K Al H 2 O 2 OH 4 is usually written as the formula of tetrahydroxoaluminate.

If the complexing agent is part of the cation, then the name of the inner sphere is composed in the same way as in the case of a complex anion, but using Russian name complexing agent and indicate the degree of its oxidation in parentheses.

Example:

Ag NH 3 2 Cl - diammine silver chloride,
Cu H 2 O 4 SO 4 - tetraaquacopper sulfate (\(II\)).

Crystal hydrates of salts

Hydrates are the products of the addition of water to particles of a substance (the term is derived from the Greek hydor- “water”).

Many salts precipitate from solutions in the form crystalline hydrates- crystals containing water molecules. In crystalline hydrates, water molecules are tightly bound to cations or anions, forming crystal lattice. Many salts of this type are essentially complex compounds. Although many of the crystal hydrates have been known since time immemorial, the systematic study of their composition was started by the Dutch chemist B. Rosebohm (\(1857\)–\(1907\)).

In the chemical formulas of crystalline hydrates, it is customary to indicate the ratio of the amount of salt substance and the amount of water substance.

Pay attention!

The dot that divides the chemical formula of crystalline hydrate into two parts, unlike mathematical expressions, does not indicate the action of multiplication and is read as the preposition “with”.

Salts are electrolytes that dissociate in aqueous solutions to form a metal cation and an acid residue anion.
The classification of salts is given in table. 9.

When writing formulas for any salts, you must be guided by one rule: the total charges of cations and anions must be equal in absolute value. Based on this, indexes should be placed. For example, when writing the formula for aluminum nitrate, we take into account that the charge of the aluminum cation is +3, and the pitrate ion is 1: AlNO 3 (+3), and using indices we equalize the charges (the least common multiple for 3 and 1 is 3. Divide 3 on absolute value charge of the aluminum cation - the index is obtained. We divide 3 by the absolute value of the charge of the NO 3 anion - we get index 3). Formula: Al(NO 3) 3

Medium, or normal, salts contain only metal cations and anions of the acid residue. Their names are derived from Latin name element forming an acidic residue by adding an appropriate ending depending on the oxidation state of that atom. For example, the sulfuric acid salt Na 2 SO 4 is called (oxidation state of sulfur +6), salt Na 2 S - (oxidation state of sulfur -2), etc. In the table. Table 10 shows the names of salts formed by the most widely used acids.

The names of the middle salts underlie all other groups of salts.

■ 106 Write the formulas of the following average salts: a) calcium sulfate; b) magnesium nitrate; c) aluminum chloride; d) zinc sulfide; d) ; f) potassium carbonate; g) calcium silicate; h) iron (III) phosphate.

Acid salts differ from average salts in that their composition, in addition to the metal cation, includes a hydrogen cation, for example NaHCO3 or Ca(H2PO4)2. An acid salt can be thought of as the product of incomplete replacement of hydrogen atoms in an acid with a metal. Consequently, acid salts can only be formed by two or more basic acids.
The molecule of an acid salt usually includes an “acidic” ion, the charge of which depends on the stage of dissociation of the acid. For example, the dissociation of phosphoric acid occurs in three steps:

At the first stage of dissociation, a singly charged anion H 2 PO 4 is formed. Consequently, depending on the charge of the metal cation, the formulas of the salts will look like NaH 2 PO 4, Ca(H 2 PO 4) 2, Ba(H 2 PO 4) 2, etc. At the second stage of dissociation, the doubly charged HPO anion is formed 2 4 — . The formulas of the salts will look like this: Na 2 HPO 4, CaHPO 4, etc. The third stage of dissociation does not produce acidic salts.
The names of acidic salts are derived from the names of the middle ones with the addition of the prefix hydro- (from the word “hydrogenium” -):
NaHCO 3 - sodium bicarbonate KHCO 4 - potassium hydrogen sulfate CaHPO 4 - calcium hydrogen phosphate
If the acidic ion contains two hydrogen atoms, for example H 2 PO 4 -, the prefix di- (two) is added to the name of the salt: NaH 2 PO 4 - sodium dihydrogen phosphate, Ca(H 2 PO 4) 2 - calcium dihydrogen phosphate, etc. d.

■ 107. Write the formulas of the following acid salts: a) calcium hydrogen sulfate; b) magnesium dihydrogen phosphate; c) aluminum hydrogen phosphate; d) barium bicarbonate; e) sodium hydrosulfite; f) magnesium hydrosulfite.
108. Is it possible to obtain acid salts of hydrochloric and nitric acid? Justify your answer.

Basic salts differ from others in that, in addition to the metal cation and the anion of the acid residue, they contain hydroxyl anions, for example Al(OH)(NO3) 2. Here the charge of the aluminum cation is +3, and the charges of the hydroxyl ion-1 and two nitrate ions are 2, for a total of 3.
The names of the main salts are derived from the names of the middle salts with the addition of the word basic, for example: Cu 2 (OH) 2 CO 3 - basic copper carbonate, Al (OH) 2 NO 3 - basic aluminum nitrate.

■ 109. Write the formulas of the following basic salts: a) basic iron (II) chloride; b) basic iron (III) sulfate; c) basic copper(II) nitrate; d) basic calcium chloride; e) basic magnesium chloride; f) basic iron (III) sulfate g) basic aluminum chloride.

Formulas of double salts, for example KAl(SO4)3, are built based on the total charges of both metal cations and the total charge of the anion

The total charge of cations is + 4, the total charge of anions is -4.
The names of double salts are formed in the same way as the middle ones, only the names of both metals are indicated: KAl(SO4)2 - potassium-aluminum sulfate.

■ 110. Write the formulas of the following salts:
a) magnesium phosphate; b) magnesium hydrogen phosphate; c) lead sulfate; d) barium hydrogen sulfate; e) barium hydrosulfite; f) potassium silicate; g) aluminum nitrate; h) copper (II) chloride; i) iron (III) carbonate; j) calcium nitrate; l) potassium carbonate.

Chemical properties of salts

1. All medium salts are strong electrolytes and easily dissociate:
Na 2 SO 4 ⇄ 2Na + + SO 2 4 —
Medium salts can interact with metals that are a number of voltages to the left of the metal that is part of the salt:
Fe + CuSO 4 = Cu + FeSO 4
Fe + Сu 2+ + SO 2 4 — = Сu + Fe 2+ + SO 2 4 —
Fe + Cu 2+ = Cu + Fe 2+
2. Salts react with alkalis and acids according to the rules described in the sections “Bases” and “Acids”:
FeCl 3 + 3NaOH = Fe(OH) 3 ↓ + 3NaCl
Fe 3+ + 3Cl - + 3Na + + 3OH - = Fe(OH) 3 + 3Na + + 3Cl -
Fe 3+ + 3OH - =Fe(OH) 3
Na 2 SO 3 + 2HCl = 2NaCl + H 2 SO 3
2Na + + SO 2 3 - + 2H + + 2Cl - = 2Na + + 2Cl - + SO 2 + H 2 O
2H + + SO 2 3 - = SO 2 + H 2 O
3. Salts can interact with each other, resulting in the formation of new salts:
AgNO 3 + NaCl = NaNO 3 + AgCl
Ag + + NO 3 - + Na + + Cl - = Na + + NO 3 - + AgCl
Ag + + Cl - = AgCl
Since these exchange reactions are carried out mainly in aqueous solutions, they occur only when one of the resulting salts precipitates.
All exchange reactions proceed in accordance with the conditions for the reactions to proceed to completion, listed in § 23, p. 89.

■ 111. Write down equations for the following reactions and, using the solubility table, determine whether they will proceed to completion:
a) barium chloride + ;
b) aluminum chloride + ;
c) sodium phosphate + calcium nitrate;
d) magnesium chloride + potassium sulfate;
e) + lead nitrate;
f) potassium carbonate + manganese sulfate;
g) + potassium sulfate.
Write the equations in molecular and ionic forms.

■ 112. Which of the following substances will iron (II) chloride react with: a) ; b) calcium carbonate; c) sodium hydroxide; d) silicon anhydride; d) ; f) copper (II) hydroxide; and) ?

113. Describe the properties of calcium carbonate as an average salt. Write all equations in molecular and ionic forms.
114. How to carry out a series of transformations:

Write all equations in molecular and ionic forms.
115. What amount of salt will be obtained from the reaction of 8 g of sulfur and 18 g of zinc?
116. What volume of hydrogen will be released when 7 g of iron reacts with 20 g of sulfuric acid?
117. How many moles of table salt will be obtained from the reaction of 120 g of sodium hydroxide and 120 g of hydrochloric acid?
118. How much potassium nitrate will be obtained from the reaction of 2 moles of potassium hydroxide and 130 g of nitric acid?

Hydrolysis of salts

A specific property of salts is their ability to hydrolyze - to undergo hydrolysis (from the Greek “hydro” - water, “lysis” - decomposition), i.e. decomposition under the influence of water. It is impossible to consider hydrolysis as decomposition in the sense in which we usually understand it, but one thing is certain - it always participates in the hydrolysis reaction.
- very weak electrolyte, dissociates poorly
H 2 O ⇄ H + + OH -
and does not change the color of the indicator. Alkalis and acids change the color of indicators, since when they dissociate in solution, an excess of OH - ions (in the case of alkalis) and H + ions in the case of acids is formed. In salts such as NaCl, K 2 SO 4, which are formed strong acid(HCl, H 2 SO 4) and a strong base (NaOH, KOH), the color indicators do not change, since in a solution of these
There is practically no hydrolysis of salts.
During the hydrolysis of salts, four cases are possible, depending on whether the salt was formed with a strong or weak acid and base.
1. If we take a salt of a strong base and a weak acid, for example K 2 S, the following will happen. Potassium sulfide dissociates into ions as a strong electrolyte:
K 2 S ⇄ 2K + + S 2-
Along with this, it weakly dissociates:
H 2 O ⇄ H + + OH —
The sulfur anion S2- is an anion of weak hydrosulfide acid, which dissociates poorly. This leads to the fact that the S 2- anion begins to attach hydrogen cations from water to itself, gradually forming low-dissociating groups:
S 2- + H + + OH — = HS — + OH —
HS - + H + + OH - = H 2 S + OH -
Since the H + cations from the water are bound, and the OH - anions remain, the reaction of the medium becomes alkaline. Thus, during the hydrolysis of salts formed by a strong base and a weak acid, the reaction of the medium is always alkaline.

■ 119.Using ionic equations, explain the process of hydrolysis of sodium carbonate.

2. If you take a salt formed by a weak base and a strong acid, for example Fe(NO 3) 3, then when it dissociates, ions are formed:
Fe(NO 3) 3 ⇄ Fe 3+ + 3NO 3 -
The Fe3+ cation is a cation of a weak base - iron, which dissociates very poorly. This leads to the fact that the Fe 3+ cation begins to attach OH - anions from water, forming slightly dissociating groups:
Fe 3+ + H + + OH - = Fe(OH) 2+ + + H +
and onwards
Fe(OH) 2+ + H + + OH - = Fe(OH) 2 + + H +
Finally, the process can reach its last stage:
Fe(OH) 2 + + H + + OH - = Fe(OH) 3 + H +
Consequently, there will be an excess of hydrogen cations in the solution.
Thus, during the hydrolysis of a salt formed by a weak base and a strong acid, the reaction of the medium is always acidic.

■ 120. Using ionic equations, explain the course of hydrolysis of aluminum chloride.

3. If a salt is formed by a strong base and a strong acid, then neither the cation nor the anion binds water ions and the reaction remains neutral. Hydrolysis practically does not occur.
4. If a salt is formed by a weak base and a weak acid, then the reaction of the medium depends on their degree of dissociation. If the base and acid have almost the same value, then the reaction of the medium will be neutral.

■ 121. It is often seen how during an exchange reaction, instead of the expected salt precipitate, a metal precipitate precipitates, for example, in the reaction between iron (III) chloride FeCl 3 and sodium carbonate Na 2 CO 3, not Fe 2 (CO 3) 3 is formed, but Fe( OH) 3 . Explain this phenomenon.
122. Among the salts listed below, indicate those that undergo hydrolysis in solution: KNO 3, Cr 2 (SO 4) 3, Al 2 (CO 3) 3, CaCl 2, K 2 SiO 3, Al 2 (SO 3) 3.

Features of the properties of acid salts

Acidic salts have slightly different properties. They can enter into reactions with the preservation and destruction of the acidic ion. For example, the reaction of an acid salt with an alkali results in the neutralization of the acid salt and the destruction of the acid ion, for example:
NaHSO4 + KOH = KNaSO4 + H2O
double salt
Na + + HSO 4 - + K + + OH - = K + + Na + + SO 2 4 - + H2O
HSO 4 - + OH - = SO 2 4 - + H2O
The destruction of an acidic ion can be represented as follows:
HSO 4 — ⇄ H + + SO 4 2-
H + + SO 2 4 - + OH - = SO 2 4 - + H2O
The acidic ion is also destroyed when reacting with acids:
Mg(HCO3)2 + 2HCl = MgCl2 + 2H2Co3
Mg 2+ + 2НСО 3 — + 2Н + + 2Сl — = Mg 2+ + 2Сl — + 2Н2O + 2СO2
2HCO 3 - + 2H + = 2H2O + 2CO2
HCO 3 - + H + = H2O + CO2
Neutralization can be carried out with the same alkali that formed the salt:
NaHSO4 + NaOH = Na2SO4 + H2O
Na + + HSO 4 - + Na + + OH - = 2Na + + SO 4 2- + H2O
HSO 4 - + OH - = SO 4 2- + H2O
Reactions with salts occur without destruction of the acidic ion:
Ca(HCO3)2 + Na2CO3 = CaCO3 + 2NaHCO3
Ca 2+ + 2НСО 3 — + 2Na + + СО 2 3 — = CaCO3↓+ 2Na + + 2НСО 3 —
Ca 2+ + CO 2 3 - = CaCO3
■ 123. Write the equations for the following reactions in molecular and ionic forms:
a) potassium hydrosulfide +;
b) sodium hydrogen phosphate + potassium hydroxide;
c) calcium dihydrogen phosphate + sodium carbonate;
d) barium bicarbonate + potassium sulfate;
e) calcium hydrosulfite +.

Obtaining salts

Based on the studied properties of the main classes inorganic substances You can deduce 10 ways to obtain salts.
1. Interaction of metal with non-metal:
2Na + Cl2 = 2NaCl
Only salts of oxygen-free acids can be obtained in this way. This is not an ionic reaction.
2. Interaction of metal with acid:
Fe + H2SO4 = FeSO4 + H2
Fe + 2H + + SO 2 4 - =Fe 2+ + SO 2 4 - + H2
Fe + 2H + = Fe 2+ + H2
3. Interaction of metal with salt:
Сu + 2AgNO3 = Cu(NO3)2 + 2Ag↓
Сu + 2Ag + + 2NO 3 - = Cu 2+ 2NO 3 - + 2Ag↓
Сu + 2Ag + = Cu 2+ + 2Ag
4. Interaction of a basic oxide with an acid:
СuО + H2SO4 = CuSO4 + H2O
CuO + 2H + + SO 2 4 - = Cu 2+ + SO 2 4 - + H2O
СuО + 2Н + = Cu 2+ + H2O
5. The interaction of a basic oxide with an acid anhydride:
3CaO + P2O5 = Ca3(PO4)2
The reaction is not ionic in nature.
6. Interaction of an acidic oxide with a base:
CO2 + Ca(OH)2 = CaCO3 + H2O
CO2 + Ca 2+ + 2OH - = CaCO3 + H2O
7, Interaction of acids with bases (neutralization):
HNO3 + KOH = KNO3 + H2O
H + + NO 3 — + K + + OH — = K + + NO 3 — + H2O
H + + OH - = H2O