Acid salts

Tasks for the application of knowledge about acid salts are found in the variants of the exam
at different difficulty levels (A, B and C). Therefore, when preparing students for the exam
the following questions need to be considered.

1. Definition and nomenclature.

Acid salts are products of incomplete replacement of hydrogen atoms of polybasic acids with a metal. The nomenclature of acid salts differs from the average ones only by adding the prefix "hydro ..." or "dihydro ..." to the name of the salt, for example: NaHCO 3 - bicarbonate sodium, Ca (H 2 RO 4) 2 - dihydrophosphate calcium.

2. Receipt.

Acid salts are obtained by the interaction of acids with metals, metal oxides, metal hydroxides, salts, ammonia, if the acid is in excess.

For example:

Zn + 2H 2 SO 4 \u003d H 2 + Zn (HSO 4) 2,

CaO + H 3 PO 4 \u003d CaHPO 4 + H 2 O,

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

Na 2 S + HCl \u003d NaHS + NaCl,

NH 3 + H 3 PO 4 \u003d NH 4 H 2 PO 4,

2NH 3 + H 3 PO 4 \u003d (NH 4) 2 HPO 4.

Acid salts are also obtained by the interaction of acid oxides with alkalis, if the oxide is in excess. For example:

CO 2 + NaOH \u003d NaHCO 3,

2SO 2 + Ca (OH) 2 \u003d Ca (HSO 3) 2.

3. Mutual transformations.

Medium salt acidic salt; for example:

K 2 CO 3 KHCO 3 .

To get an acidic salt from an average salt, you need to add an excess of acid or the corresponding oxide and water:

K 2 CO 3 + H 2 O + CO 2 \u003d 2KHCO 3.

To get an average salt from an acid salt, you need to add an excess of alkali:

KHCO 3 + KOH \u003d K 2 CO 3 + H 2 O.

Hydrocarbonates decompose to form carbonates upon boiling:

2KHCO 3 K 2 CO 3 + H 2 O + CO 2.

4. Properties.

Acid salts show properties of acids, interact with metals, metal oxides, metal hydroxides, salts.

For example:

2KНSO 4 + Mg \u003d H 2 + MgSO 4 + K 2 SO 4,

2KHSO 4 + MgO \u003d H 2 O + MgSO 4 + K 2 SO 4,

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

2KHSO 4 + Cu(OH) 2 \u003d 2H 2 O + K 2 SO 4 + CuSO 4,

2KHSO 4 + MgCO 3 \u003d H 2 O + CO 2 + K 2 SO 4 + MgSO 4,

2KHSO 4 + BaCl 2 = BaSO 4 + K 2 SO 4 + 2HCl.

5. Tasks for acid salts. The formation of one salt.

When solving problems for excess and deficiency, one must remember about the possibility of the formation of acid salts, so first they make up the equations of all possible reactions. After finding the quantities of reacting substances, they make a conclusion about what kind of salt will turn out, and solve the problem according to the corresponding equation.

Task 1. 44.8 l of CO 2 were passed through a solution containing 60 g of NaOH. Find the mass of salt formed.

Solution

(NaOH) = m/M= 60 (g)/40 (g/mol) = 1.5 mol;

(CO 2) = V/Vm\u003d 44.8 (l) / 22.4 (l / mol) \u003d 2 mol.

Since (NaOH): (CO 2) \u003d 1.5: 2 \u003d 0.75: 1, we conclude that CO 2 is in excess, therefore, an acid salt will be obtained:

NaOH + CO 2 \u003d NaHCO 3.

The amount of substance of the formed salt is equal to the amount of substance of the reacted sodium hydroxide:

(NaHCO 3) = 1.5 mol.

m(NaHCO3) = M\u003d 84 (g / mol) 1.5 (mol) \u003d 126 g.

Answer: m(NaHCO 3) = 126 g.

Task 2. Phosphorus(V) oxide weighing 2.84 g was dissolved in 120 g of 9% phosphoric acid. The resulting solution was boiled, then 6 g of sodium hydroxide was added to it. Find the mass of the resulting salt.

Given:	Find: m(salts).
m(P 2 O 5) \u003d 2.84 g,
m( p-ra) (H 3 PO 4) = 120 g,
(H 3 PO 4) \u003d 9%,
m(NaOH) = 6 g.

Solution

(P 2 O 5) = m/M\u003d 2.84 (g) / 142 (g / mol) \u003d 0.02 mol,

therefore, 1 (H 3 PO 4 received) \u003d 0.04 mol.

m(H 3 PO 4) = m(solution) \u003d 120 (g) 0.09 \u003d 10.8 g.

2 (H 3 PO 4) = m/M\u003d 10.8 (g) / 98 (g / mol) \u003d 0.11 mol,

(H 3 PO 4) \u003d 1 + 2 \u003d 0.11 + 0.04 \u003d 0.15 mol.

(NaOH) = m/M\u003d 6 (g) / 40 (g / mol) \u003d 0.15 mol.

Because the

(H 3 PO 4): (NaOH) = 0.15: 0.15 = 1: 1,

then you get sodium dihydrogen phosphate:

(NaH 2 PO 4) = 0.15 mol,

m(NaH 2 PO 4) \u003d M \u003d 120 (g / mol) 0.15 (mol) \u003d 18 g.

Answer: m(NaH 2 PO 4) = 18 g.

Task 3. Hydrogen sulfide with a volume of 8.96 liters was passed through 340 g of a 2% ammonia solution. Name the salt resulting from the reaction and determine its mass.

Answer: ammonium hydrosulfide,
m(NH 4 HS) = 20.4 g.

Problem 4. The gas obtained by burning 3.36 liters of propane reacted with 400 ml of a 6% potassium hydroxide solution (= 1.05 g/ml). Find the composition of the resulting solution and the mass fraction of salt in the resulting solution.

Answer:(KHCO 3) = 10.23%.

Task 5. All carbon dioxide, obtained by burning 9.6 kg of coal, was passed through a solution containing 29.6 kg of calcium hydroxide. Find the mass of the resulting salt.

Answer: m(Ca (HCO 3) 2) = 64.8 kg.

Task 6. 1.3 kg of zinc was dissolved in 9.8 kg of a 20% sulfuric acid solution. Find the mass of the resulting salt.

Answer: m(ZnSO 4) = 3.22 kg.

6. Tasks for acid salts. The formation of a mixture of two salts.

This is a more complex version of acid salt problems. Depending on the amount of reactants, the formation of a mixture of two salts is possible.

For example, when neutralizing phosphorus(V) oxide with alkali, depending on the molar ratio of the reactants, the following products can be formed:

P 2 O 5 + 6NaOH \u003d 2Na 3 PO 4 + 3H 2 O,

(P 2 O 5): (NaOH) = 1:6;

P 2 O 5 + 4NaOH \u003d 2Na 2 HPO 4 + H 2 O,

(P 2 O 5): (NaOH) = 1:4;

P 2 O 5 + 2NaOH + H 2 O \u003d 2NaH 2 PO 4,

(P 2 O 5): (NaOH) = 1:2.

It should be remembered that with incomplete neutralization, the formation of a mixture of two compounds is possible. When interacting 0.2 mol P 2 O 5 with an alkali solution containing 0.9 mol NaOH, the molar ratio is between 1:4 and 1:6. In this case, a mixture of two salts is formed: sodium phosphate and sodium hydrogen phosphate.

If the alkali solution contains 0.6 mol of NaOH, then the molar ratio will be different: 0.2:0.6 \u003d 1:3, it is between 1:2 and 1:4, so a mixture of two other salts will be obtained: dihydrogen phosphate and hydrogen phosphate sodium.

These tasks can be solved different ways. We will proceed from the assumption that two reactions occur simultaneously.

A l g o r i t m e n t i o n

1. Write equations for all possible reactions.

2. Find the amounts of reacting substances and, by their ratio, determine the equations of two reactions that occur simultaneously.

3. Denote the amount of one of the reactants in the first equation as X moth, in the second - at mol.

4. Express via X and at amounts of another reactant according to the molar ratios of the equations.

5. Compose a system of equations with two unknowns.

Task 1. Phosphorus(V) oxide, obtained by burning 6.2 g of phosphorus, was passed through 200 g of an 8.4% potassium hydroxide solution. What substances and in what quantities are obtained?

Given:	Find: 1 ; 2 .
m(P) = 6.2 g,
m(solution KOH) = 200 g,
(KOH) = 8.4%.

Solution

(P) = m/M\u003d 6.2 (g) / 31 (g / mol) \u003d 0.2 mol,

Answer.((NH 4) 2 HPO 4) = 43.8%,
(NH 4 H 2 PO 4) = 12.8%.

Problem 4. To 50 g of a solution of phosphoric acid with mass fraction 11.76% added 150 g of potassium hydroxide solution with a mass fraction of 5.6%. Find the composition of the residue obtained by evaporating the solution.

Answer: m(K 3 PO 4) = 6.36 g,
m(K 2 HPO 4) = 5.22 g.

Problem 5. We burned 5.6 liters of butane (N.O.) and the resulting carbon dioxide was passed through a solution containing 102.6 g of barium hydroxide. Find the masses of the resulting salts.

Answer: m(BaCO 3) \u003d 39.4 g,
m(Ba (HCO 3) 2) \u003d 103.6 g.

Chemical properties of salts

Salts should be considered as a product of the interaction of an acid and a base. As a result, they can form:

1. normal (medium) - are formed when the amount of acid and base is sufficient for complete interaction. Names of normal salts and consist of two parts. First, the anion (acid residue) is called, then the cation.
2. sour - formed when there is an excess of acid not enough alkali, because in this case there are not enough metal cations to replace all the hydrogen cations present in the acid molecule. As part of the acid residues of this type of salt, you will always see hydrogen. Acid salts are formed only by polybasic acids and exhibit the properties of both salts and acids. In the names of acid salts a prefix is ​​put hydro- to the anion.
3. basic salts - are formed with an excess of base and an insufficient amount of acid, because in this case the anions of acid residues are not enough to completely replace the hydroxo groups present in the base. basic salts in the composition of cations contain hydroxo groups. Basic salts are possible for polyacid bases, but not for monoacid ones. Some basic salts are able to decompose on their own, while releasing water, forming oxosalts, which have the properties of basic salts. Name of basic salts is constructed as follows: the prefix is ​​added to the anion hydroxo-.

Typical reactions of normal salts

• They react well with metals. At the same time, more active metals displace less active ones from solutions of their salts.
• With acids, alkalis and other salts, the reactions go to completion, provided that a precipitate, gas, or poorly dissociated compounds are formed.
• In the reactions of salts with alkalis, substances such as nickel (II) hydroxide Ni (OH) 2 are formed - a precipitate; ammonia NH 3 - gas; water H 2 O is a weak electrolyte, a low-dissociation compound:
• Salts react with each other if a precipitate is formed or if a more stable compound is formed.
• Many normal salts decompose when heated to form two oxides, acidic and basic.
• Nitrates decompose in a different way than other normal salts. When heated, alkali and alkaline earth metal nitrates release oxygen and turn into nitrites:
• Nitrates of almost all other metals decompose to oxides:
• Nitrates of some heavy metals (silver, mercury, etc.) decompose when heated to metals:

Typical reactions of acid salts

• They enter into all those reactions that acids enter into. They react with alkalis, if the acid salt and alkali contain the same metal, then a normal salt is formed as a result.
• If the alkali contains another metal, then double salts are formed.

Typical reactions of basic salts

• These salts undergo the same reactions as the bases. They react with acids, if the basic salt and acid contain the same acid residue, then a normal salt is formed as a result.
• If the acid contains another acid residue, then double salts are formed.

Complex salts- connection, in knots crystal lattice containing complex ions.

Bases can interact:

• with non-metals

  6KOH + 3S → K2SO 3 + 2K 2 S + 3H 2 O;

• with acidic oxides -

  2NaOH + CO 2 → Na 2 CO 3 + H 2 O;

• with salts (precipitation, gas release) -

  2KOH + FeCl 2 → Fe(OH) 2 + 2KCl.

There are also other ways to get:

• the interaction of two salts -

  CuCl 2 + Na 2 S → 2NaCl + CuS↓;

• reaction of metals and non-metals -
• combination of acidic and basic oxides -

  SO 3 + Na 2 O → Na 2 SO 4;

• interaction of salts with metals -

  Fe + CuSO 4 → FeSO 4 + Cu.

Chemical properties

Soluble salts are electrolytes and are subject to dissociation reactions. When interacting with water, they disintegrate, i.e. dissociate into positively and negatively charged ions - cations and anions, respectively. Metal ions are cations, acid residues are anions. Examples of ionic equations:

• NaCl → Na + + Cl - ;
• Al 2 (SO 4) 3 → 2Al 3 + + 3SO 4 2− ;
• CaClBr → Ca2 + + Cl - + Br - .

In addition to metal cations, ammonium (NH4 +) and phosphonium (PH4 +) cations may be present in salts.

Other reactions are described in the table of chemical properties of salts.

Rice. 3. Isolation of sediment upon interaction with bases.

Some salts, depending on the type, decompose when heated into a metal oxide and an acid residue or into simple substances. For example, CaCO 3 → CaO + CO 2, 2AgCl → Ag + Cl 2.

What have we learned?

From the 8th grade chemistry lesson, we learned about the features and types of salts. Complex inorganic compounds composed of metals and acid residues. May include hydrogen (acid salts), two metals, or two acid residues. These are solid crystalline substances that are formed as a result of the reactions of acids or alkalis with metals. React with bases, acids, metals, other salts.

Chemical Equations

chemical equation is the expression for the reaction chemical formulas. Chemical Equations show which substances enter into a chemical reaction and which substances are formed as a result of this reaction. The equation is compiled on the basis of the law of conservation of mass and shows the quantitative ratios of substances involved in a chemical reaction.

As an example, consider the interaction of potassium hydroxide with phosphoric acid:

H 3 RO 4 + 3 KOH \u003d K 3 RO 4 + 3 H 2 O.

It can be seen from the equation that 1 mole of phosphoric acid (98 g) reacts with 3 moles of potassium hydroxide (3 56 g). As a result of the reaction, 1 mol of potassium phosphate (212 g) and 3 mol of water (3 18 g) are formed.

98 + 168 = 266 g; 212 + 54 = 266 g we see that the mass of the substances that entered into the reaction is equal to the mass of the reaction products. The chemical reaction equation allows you to produce various calculations associated with this reaction.

Compounds are divided into four classes: oxides, bases, acids and salts.

oxides are complex substances consisting of two elements, one of which is oxygen, i.e. an oxide is a compound of an element with oxygen.

The name of oxides is formed from the name of the element that is part of the oxide. For example, BaO is barium oxide. If the oxide element has a variable valency, then after the name of the element in brackets its valence is indicated by a Roman numeral. For example, FeO is iron (I) oxide, Fe2O3 is iron (III) oxide.

All oxides are divided into salt-forming and non-salt-forming.

Salt-forming oxides are those oxides which, as a result of chemical reactions form salts. These are oxides of metals and non-metals, which, when interacting with water, form the corresponding acids, and when interacting with bases, the corresponding acidic and normal salts. For example, copper oxide (CuO) is a salt-forming oxide, because, for example, when it interacts with hydrochloric acid (HCl), a salt is formed:

CuO + 2HCl → CuCl2 + H2O.

As a result of chemical reactions, other salts can be obtained:

CuO + SO3 → CuSO4.

Non-salt-forming oxides are those oxides that do not form salts. Examples are CO, N2O, NO.

Salt-forming oxides are of 3 types: basic (from the word "base"), acidic and amphoteric.

Basic oxides are oxides of metals, which correspond to hydroxides belonging to the class of bases. Basic oxides include, for example, Na2O, K2O, MgO, CaO, etc.

Chemical properties of basic oxides

1. Water-soluble basic oxides react with water to form bases:

Na2O + H2O → 2NaOH.

2. Interact with acid oxides, forming the corresponding salts

Na2O + SO3 → Na2SO4.

3. React with acids to form salt and water:

CuO + H2SO4 → CuSO4 + H2O.

4. React with amphoteric oxides:

Li2O + Al2O3 → 2LiAlO2.

5. Basic oxides react with acidic oxides to form salts:

Na2O + SO3 = Na2SO4

If the second element in the composition of oxides is a non-metal or a metal exhibiting a higher valency (usually exhibits from IV to VII), then such oxides will be acidic. Acid oxides (acid anhydrides) are oxides that correspond to hydroxides belonging to the class of acids. These are, for example, CO2, SO3, P2O5, N2O3, Cl2O5, Mn2O7, etc. Acid oxides dissolve in water and alkalis, forming salt and water.

Chemical properties of acid oxides

1. Interact with water, forming acid:

SO3 + H2O → H2SO4.

But not all acidic oxides directly react with water (SiO2, etc.).

2. React with based oxides to form a salt:

CO2 + CaO → CaCO3

3. Interact with alkalis, forming salt and water:

CO2 + Ba(OH)2 → BaCO3 + H2O.

Amphoteric oxide contains an element that has amphoteric properties. Amphotericity is understood as the ability of compounds to exhibit acidic and basic properties depending on the conditions. For example, zinc oxide ZnO can be both a base and an acid (Zn(OH)2 and H2ZnO2). Amphotericity is expressed in the fact that, depending on the conditions, amphoteric oxides exhibit either basic or acidic properties, for example, Al2O3, Cr2O3, MnO2; Fe2O3 ZnO. For example, the amphoteric nature of zinc oxide manifests itself when it interacts with both hydrochloric acid and sodium hydroxide:

ZnO + 2HCl = ZnCl 2 + H 2 O

ZnO + 2NaOH \u003d Na 2 ZnO 2 + H 2 O

Since not all amphoteric oxides are soluble in water, it is much more difficult to prove the amphotericity of such oxides. For example, aluminum oxide (III) in the reaction of its fusion with potassium disulfate exhibits basic properties, and when fused with hydroxides, acidic:

Al2O3 + 3K2S2O7 = 3K2SO4 + A12(SO4)3

Al2O3 + 2KOH = 2KAlO2 + H2O

For various amphoteric oxides, the duality of properties can be expressed in terms of varying degrees. For example, zinc oxide is equally easily soluble in both acids and alkalis, and iron (III) oxide - Fe2O3 - has predominantly basic properties.

Chemical properties of amphoteric oxides

1. Interact with acids to form salt and water:

ZnO + 2HCl → ZnCl2 + H2O.

2. React with solid alkalis (during fusion), forming as a result of the reaction salt - sodium zincate and water:

ZnO + 2NaOH → Na2 ZnO2 + H2O.

When zinc oxide interacts with an alkali solution (the same NaOH), another reaction occurs:

ZnO + 2 NaOH + H2O => Na2.

Coordination number - a characteristic that determines the number of nearest particles: atoms or ions in a molecule or crystal. Each amphoteric metal has its own coordination number. For Be and Zn, this is 4; For and Al is 4 or 6; For and Cr is 6 or (very rarely) 4;

Amphoteric oxides usually do not dissolve in water and do not react with it.

Methods for obtaining oxides from simple substances are either a direct reaction of an element with oxygen:

or decomposition of complex substances:

a) oxides

4CrO3 = 2Cr2O3 + 3O2-

b) hydroxides

Ca(OH)2 = CaO + H2O

c) acids

H2CO3 = H2O + CO2-

CaCO3 = CaO +CO2

As well as the interaction of acids - oxidizing agents with metals and non-metals:

Cu + 4HNO3 (conc) = Cu(NO3) 2 + 2NO2 + 2H2O

Oxides can be obtained by direct interaction of oxygen with another element, or indirectly (for example, by the decomposition of salts, bases, acids). AT normal conditions oxides are in solid, liquid and gaseous state, this type of compounds is very common in nature. Oxides are found in the Earth's crust. Rust, sand, water, carbon dioxide are oxides.

Foundations- These are complex substances in the molecules of which the metal atoms are connected to one or more hydroxyl groups.

Bases are electrolytes that, upon dissociation, form only hydroxide ions as anions.

NaOH \u003d Na + + OH -

Ca (OH) 2 \u003d CaOH + + OH - \u003d Ca 2 + + 2OH -

There are several signs of classification of bases:

Based on their solubility in water, bases are divided into alkalis and insolubles. Alkalis are hydroxides of alkali metals (Li, Na, K, Rb, Cs) and alkaline earth metals (Ca, Sr, Ba). All other bases are insoluble.

Depending on the degree of dissociation, bases are divided into strong electrolytes (all alkalis) and weak electrolytes (insoluble bases).

Depending on the number of hydroxyl groups in the molecule, the bases are divided into single acid (1 OH group), for example, sodium hydroxide, potassium hydroxide, diacid (2 OH groups), for example, calcium hydroxide, copper (2) hydroxide, and polyacid.

Chemical properties.

OH ions - in solution determine the alkaline environment.

Alkali solutions change the color of indicators:

Phenolphthalein: colorless ® raspberry,

Litmus: violet ® blue,

Methyl orange: orange ® yellow.

Alkali solutions interact with acid oxides to form salts of those acids that correspond to the reacting acid oxides. Depending on the amount of alkali, medium or acidic salts are formed. For example, when calcium hydroxide reacts with carbon monoxide (IV), calcium carbonate and water are formed:

Ca(OH)2 + CO2 = CaCO3? + H2O

And when calcium hydroxide interacts with an excess of carbon monoxide (IV), calcium bicarbonate is formed:

Ca(OH)2 + CO2 = Ca(HCO3)2

Ca2+ + 2OH- + CO2 = Ca2+ + 2HCO32-

All bases react with acids to form a salt and water, for example: when sodium hydroxide reacts with hydrochloric acid, sodium chloride and water are formed:

NaOH + HCl = NaCl + H2O

Na+ + OH- + H+ + Cl- = Na+ + Cl- + H2O

Copper (II) hydroxide dissolves in hydrochloric acid to form copper (II) chloride and water:

Cu(OH)2 + 2HCl = CuCl2 + 2H2O

Cu(OH)2 + 2H+ + 2Cl- = Cu2+ + 2Cl- + 2H2O

Cu(OH)2 + 2H+ = Cu2+ + 2H2О.

The reaction between an acid and a base is called a neutralization reaction.

Insoluble bases, when heated, decompose into water and a metal oxide corresponding to the base, for example:

Cu(OH)2 = CuO + H2 2Fe(OH)3 = Fe2O3 + 3H2O

Alkalis interact with salt solutions if one of the conditions for the ion exchange reaction to proceed to completion (precipitate) is met,

2NaOH + CuSO4 = Cu(OH)2? + Na2SO4

2OH- + Cu2+ = Cu(OH)2

The reaction proceeds due to the binding of copper cations with hydroxide ions.

When barium hydroxide reacts with a solution of sodium sulfate, a precipitate of barium sulfate is formed.

Ba(OH)2 + Na2SO4 = BaSO4? + 2NaOH

Ba2+ + SO42- = BaSO4

The reaction proceeds due to the binding of barium cations and sulfate anions.

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

According to the presence or absence of oxygen in the acid molecule, they are divided into oxygen-containing acids (H2SO4 sulfuric acid, H2SO3 sulfurous acid, HNO3 nitric acid, H3PO4 phosphoric acid, H2CO3 carbonic acid, H2SiO3 silicic acid) and anoxic (HF hydrofluoric acid, HCl hydrochloric acid (hydrochloric acid), HBr hydrobromic acid, HI hydroiodic acid, H2S hydrosulfide acid).

Depending on the number of hydrogen atoms in an acid molecule, acids are monobasic (with 1 H atom), dibasic (with 2 H atoms) and tribasic (with 3 H atoms).

A C S L O T S

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

Acid residues can consist of one atom (-Cl, -Br, -I) - these are simple acid residues, or they can be from a group of atoms (-SO3, -PO4, -SiO3) - these are complex residues.

AT aqueous solutions in exchange and substitution reactions, acid residues are not destroyed:

H2SO4 + CuCl2 → CuSO4 + 2 HCl

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

H2SO4 - H2O → SO3. Anoxic acids do not have anhydrides.

Acids get their name from the name of the acid-forming element (acid-forming agent) with the addition of the endings “naya” and less often “vaya”: H2SO4 - sulfuric; H2SO3 - coal; H2SiO3 - silicon, etc.

The element can form several oxygen acids. In this case, the indicated endings in the name of the acids will be when the element exhibits the highest valence (the acid molecule has a large content of oxygen atoms). If the element exhibits a lower valence, the ending in the name of the acid will be “pure”: HNO3 - nitric, HNO2 - nitrous.

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

H2 + Cl2 → 2 HCl;

Solutions of the resulting gaseous substances HCl and H2S are acids.

Under normal conditions, acids are both liquid and solid.

Chemical properties of acids

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

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

2. Interact with bases to form water and salt, which contains an unchanged acid residue (neutralization reaction):

H2SO4 + Ca(OH)2 → CaSO4 + 2 H2O.

3. React with based oxides to form water and salt. The salt contains the acid residue of the acid that was used in the neutralization reaction:

H3PO4 + Fe2O3 → 2 FePO4 + 3 H2O.

4. Interact with metals.

For the interaction of acids with metals, certain conditions must be met:

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

K, Ca, Na, Mn, Al, Zn, Fe, Ni, Sn, Pb, H2, Cu, Hg, Ag, Au.

But the reaction between a solution of hydrochloric acid and copper is impossible, since copper is in the series of voltages after hydrogen.

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

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

Zn + 2HCl → ZnCl2 + H2;

Cu + 4HNO3 → CuNO3 + 2 NO2 + 2 H2O.

However, no matter how different the acids are, they all form hydrogen cations during dissociation, which determine the series common properties: sour taste, discoloration of indicators (litmus and methyl orange), interaction with other substances.

The same reaction proceeds between metal oxides and most acids

CuO+ H2SO4 = CuSO4+ H2O

Let's describe the reactions:

2) In the second reaction, a soluble salt should be obtained. In many cases, the interaction of metal with acid practically does not occur because the resulting salt is insoluble and covers the surface of the metal with a protective film, for example:

Рb + H2SO4 =/ PbSO4 + H2

Insoluble lead (II) sulfate stops the access of the acid to the metal, and the reaction stops as soon as it starts. For this reason, most heavy metals practically do not interact with phosphoric, carbonic and hydrosulfide acids.

3) The third reaction is characteristic of acid solutions, therefore, insoluble acids, such as silicic acid, do not react with metals. Concentrated sulfuric acid solution and solution nitric acid of any concentration interact with metals in a slightly different way, therefore the equations of reactions between metals and these acids are written in a different scheme. A dilute solution of sulfuric acid reacts with metals. standing in a series of voltages up to hydrogen, forming a salt and hydrogen.

4) The fourth reaction is a typical ion exchange reaction and only proceeds if a precipitate or gas is formed.

Salts - these are complex substances whose molecules consist of metal atoms and acidic residues (sometimes they may contain hydrogen). For example, NaCl is sodium chloride, CaSO4 is calcium sulfate, etc.

Almost all salts are ionic compounds, therefore, ions of acid residues and metal ions are interconnected in salts:

Na+Cl - sodium chloride

Ca2+SO42 - calcium sulfate, etc.

Salt is a product of partial or complete replacement of acid hydrogen atoms by a metal.

Hence, the following types of salts are distinguished:

1. Medium salts - all hydrogen atoms in the acid are replaced by a metal: Na2CO3, KNO3, etc.

2. Acid salts - not all hydrogen atoms in the acid are replaced by a metal. Of course, acid salts can only form dibasic or polybasic acids. Monobasic acids cannot give acid salts: NaHCO3, NaH2PO4, etc. d.

3. Double salts - hydrogen atoms of a dibasic or polybasic acid are replaced not by one metal, but by two different ones: NaKCO3, KAl(SO4)2, etc.

4. Basic salts can be considered as products of incomplete or partial replacement of hydroxyl groups of bases by acidic residues: Al(OH)SO4, Zn(OH)Cl, etc.

According to international nomenclature, the name of the salt of each acid comes from the Latin name of the element. For example, salts of sulfuric acid are called sulfates: CaSO4 - calcium sulfate, MgSO4 - magnesium sulfate, etc.; salts of hydrochloric acid are called chlorides: NaCl - sodium chloride, ZnCI2 - zinc chloride, etc.

The particle “bi” or “hydro” is added to the name of salts of dibasic acids: Mg (HCl3) 2 - magnesium bicarbonate or bicarbonate.

Provided that in a tribasic acid only one hydrogen atom is replaced by a metal, then the prefix “dihydro” is added: NaH2PO4 is sodium dihydrogen phosphate.

Salts are solid substances that have the most different solubility in water.

The chemical properties of salts are determined by the properties of the cations and anions that are part of their composition.

1. Some salts decompose when calcined:

CaCO3 = CaO + CO2

2. React with acids to form a new salt and a new acid. For this reaction to occur, it is necessary that the acid be stronger than the salt that the acid acts on:

2NaCl + H2SO4 → Na2SO4 + 2HCl.

3. Interact with bases, forming a new salt and a new base:

Ba(OH)2 + MgSO4 → BaSO4↓ + Mg(OH)2.

4. Interact with each other to form new salts:

NaCl + AgNO3 → AgCl + NaNO3 .

5. Interact with metals that are in the range of activity up to the metal that is part of the salt.

salts complex substances are called, the molecules of which consist of metal atoms and acid residues (sometimes they may contain hydrogen). For example, NaCl is sodium chloride, CaSO 4 is calcium sulfate, etc.

Practically All salts are ionic compounds therefore, in salts, ions of acid residues and metal ions are interconnected:

Na + Cl - - sodium chloride

Ca 2+ SO 4 2– - calcium sulfate, etc.

Salt is a product of partial or complete replacement of acid hydrogen atoms by a metal. Hence, the following types of salts are distinguished:

1. Medium salts- all hydrogen atoms in the acid are replaced by a metal: Na 2 CO 3, KNO 3, etc.

2. Acid salts- not all hydrogen atoms in the acid are replaced by a metal. Of course, acid salts can only form dibasic or polybasic acids. Monobasic acids cannot give acid salts: NaHCO 3, NaH 2 PO 4, etc. d.

3. Double salts- hydrogen atoms of a dibasic or polybasic acid are replaced not by one metal, but by two different ones: NaKCO 3, KAl(SO 4) 2, etc.

4. Basic salts can be considered as products of incomplete or partial substitution of hydroxyl groups of bases by acidic residues: Al(OH)SO 4 , Zn(OH)Cl, etc.

According to international nomenclature, the name of the salt of each acid comes from the Latin name of the element. For example, salts of sulfuric acid are called sulfates: CaSO 4 - calcium sulfate, Mg SO 4 - magnesium sulfate, etc.; salts of hydrochloric acid are called chlorides: NaCl - sodium chloride, ZnCI 2 - zinc chloride, etc.

The particle "bi" or "hydro" is added to the name of salts of dibasic acids: Mg (HCl 3) 2 - magnesium bicarbonate or bicarbonate.

Provided that in a tribasic acid only one hydrogen atom is replaced by a metal, then the prefix "dihydro" is added: NaH 2 PO 4 - sodium dihydrogen phosphate.

Salts are solid substances that have a wide range of solubility in water.

Chemical properties of salts

The chemical properties of salts are determined by the properties of the cations and anions that are part of their composition.

1. Some salts decompose when calcined:

CaCO 3 \u003d CaO + CO 2

2. React with acids to form a new salt and a new acid. For this reaction to occur, it is necessary that the acid be stronger than the salt that the acid acts on:

2NaCl + H 2 SO 4 → Na 2 SO 4 + 2HCl.

3. Interact with bases, forming a new salt and a new base:

Ba(OH) 2 + MgSO 4 → BaSO 4 ↓ + Mg(OH) 2 .

4. Interact with each other with the formation of new salts:

NaCl + AgNO 3 → AgCl + NaNO 3 .

5. Interact with metals, which are in the range of activity to the metal that is part of the salt:

Fe + CuSO 4 → FeSO 4 + Cu↓.

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