Acids- electrolytes, upon 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.

At normal conditions significant amount inorganic acids exist in the liquid state, some in the solid state (H 3 PO 4, H 3 BO 3).

Organic acids with up to 3 carbon atoms are highly mobile, colorless liquids with a characteristic pungent odor; acids with 4-9 carbon atoms - oily liquids with unpleasant smell, and acids with a large number of carbon atoms are solids insoluble in water.

Chemical formulas of acids

Let us 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 H 5 COOH. 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) = 1 amu, Ar(Cl) = 35.5 amu. amu, Ar(P) = 31 amu, Ar(O) = 16 amu, Ar(S) = 32 amu, Ar(C) = 12 a.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) = 2×1 + 32 + 4×16 = 2 + 32 + 64 = 98.

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

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

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

Mr(CH 3 COOH) = 3×12 + 4×1 + 2×16 = 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) = 7 × 12 + 6 × 1 + 2 × 16 = 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 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 it is known that its molar mass is 180 g/mol.
Solution Let’s draw up a diagram of the combustion reaction of an organic compound, designating 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. Values ​​of relative atomic masses taken from the Periodic Table of D.I. Mendeleev, round to whole numbers: Ar(C) = 12 amu, Ar(H) = 1 amu, Ar(O) = 16 amu.

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);

Let's 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) = Ar(C) + 2×Ar(O) = 12+ 2×16 = 12 + 32 = 44 g/mol;

M(H 2 O) = 2×Ar(H) + Ar(O) = 2×1+ 16 = 2 + 16 = 18 g/mol.

m(C) = ×12 = 2.4 g;

m(H) = 2 × 3.6 / 18 × 1 = 0.4 g.

m(O) = m(C x H y O z) - m(C) - m(H) = 6 - 2.4 - 0.4 = 3.2 g.

Let's determine 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.

This means the simplest formula of the compound is CH 2 O and the molar mass is 30 g/mol.

To find the true formula of an organic compound, we find the ratio of the true and resulting molar masses:

M substance / M(CH 2 O) = 180 / 30 = 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 be C 6 H 12 O 6. This is 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%.
Solution The mass fraction of element X in a molecule of the composition NX is calculated using the following formula:

ω (X) = n × Ar (X) / M (HX) × 100%.

Let us denote the number of phosphorus atoms in the molecule by “x”, and the number of oxygen atoms by “y”

Let's find the corresponding relative atomic masses of the elements phosphorus and oxygen (the values ​​of the relative atomic masses taken from D.I. Mendeleev's Periodic Table are rounded to whole numbers).

Ar(P) = 31; Ar(O) = 16.

We divide the percentage content of elements into 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 combining phosphorus and oxygen is P 2 O 5 . It is phosphorus(V) oxide.
Answer P2O5

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 sour taste and are capable of dissociating into aquatic environment(break 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.

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 plant origin: acetic, lactic, nicotine, ascorbic acid. 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.
Oxygen-free: Basicity Name of salt
HCl - hydrochloric (hydrochloric) monobasic chloride
HBr - hydrobromic monobasic bromide
HI - hydroiodide monobasic iodide
HF - hydrofluoric (fluoric) monobasic fluoride
H 2 S - hydrogen sulfide dibasic sulfide
Oxygen-containing:
HNO 3 – nitrogen monobasic nitrate
H 2 SO 3 - sulfurous dibasic sulfite
H 2 SO 4 – sulfuric dibasic sulfate
H 2 CO 3 - coal dibasic carbonate
H 2 SiO 3 - silicon dibasic silicate
H 3 PO 4 - orthophosphoric tribasic orthophosphate

Salts – complex substances that consist of metal atoms and acidic residues. This is the most numerous class of inorganic compounds.

Classification. By composition and properties: medium, acidic, basic, double, mixed, complex

Medium salts are products of complete replacement of hydrogen atoms of a polybasic acid with metal atoms.

Upon dissociation, only metal cations (or NH 4 +) are produced. For example:

Na 2 SO 4 ® 2Na + +SO

CaCl 2 ® Ca 2+ + 2Cl -

Acid salts are products of incomplete replacement of hydrogen atoms of a polybasic acid with metal atoms.

Upon dissociation, they produce metal cations (NH 4 +), hydrogen ions and anions of the acid residue, for example:

NaHCO 3 ® Na + + HCO « H + +CO .

Basic salts are products of incomplete replacement of OH groups - the corresponding base with acidic residues.

Upon dissociation, they give metal cations, hydroxyl anions and an acid residue.

Zn(OH)Cl ® + + Cl - « Zn 2+ + OH - + Cl - .

Double salts contain two metal cations and upon dissociation give two cations and one anion.

KAl(SO 4) 2 ® K + + Al 3+ + 2SO

Complex salts contain complex cations or anions.

Br ® + + Br - « Ag + +2 NH 3 + Br -

Na ® Na + + - « Na + + Ag + + 2 CN -

Genetic connection between different classes of connections

EXPERIMENTAL

Equipment and utensils: stand with test tubes, washing machine, alcohol lamp.

Reagents and materials: red phosphorus, zinc oxide, Zn granules, slaked lime powder Ca(OH) 2, 1 mol/dm 3 solutions of NaOH, ZnSO 4, CuSO 4, AlCl 3, FeCl 3, HСl, H 2 SO 4, universal indicator paper, solution phenolphthalein, methyl orange, distilled water.

Work order

1. Pour zinc oxide into two test tubes; add an acid solution (HCl or H 2 SO 4) to one and an alkali solution (NaOH or KOH) to the other and heat slightly on an alcohol lamp.

Observations: Does zinc oxide dissolve in an acid and alkali solution?

Write equations

Conclusions: 1.What type of oxide does ZnO belong to?

2. What properties do amphoteric oxides have?

Preparation and properties of hydroxides

2.1. Dip the tip of the universal indicator strip into the alkali solution (NaOH or KOH). Compare the resulting color of the indicator strip with the standard color scale.

Observations: Record the pH value of the solution.

2.2. Take four test tubes, pour 1 ml of ZnSO 4 solution into the first, CuSO 4 into the second, AlCl 3 into the third, and FeCl 3 into the fourth. Add 1 ml of NaOH solution to each test tube. Write observations and equations for the reactions occurring.

Observations: Does precipitation occur when alkali is added to a salt solution? Indicate the color of the sediment.

Write equations occurring reactions (in molecular and ionic form).

Conclusions: How can metal hydroxides be prepared?

2.3. Transfer half of the sediments obtained in experiment 2.2 to other test tubes. Treat one part of the sediment with a solution of H 2 SO 4 and the other with a solution of NaOH.

Observations: Does precipitate dissolution occur when alkali and acid are added to precipitates?

Write equations occurring reactions (in molecular and ionic form).

Conclusions: 1. What type of hydroxides are Zn(OH) 2, Al(OH) 3, Cu(OH) 2, Fe(OH) 3?

2. What properties do amphoteric hydroxides have?

Obtaining salts.

3.1. Pour 2 ml of CuSO 4 solution into a test tube and dip a cleaned nail into this solution. (The reaction is slow, changes on the surface of the nail appear after 5-10 minutes).

Observations: Are there any changes to the surface of the nail? What is being deposited?

Write the equation for the redox reaction.

Conclusions: Taking into account the range of metal stresses, indicate the method of obtaining salts.

3.2. Place one zinc granule in a test tube and add HCl solution.

Observations: Is there any gas evolution?

Write the equation

Conclusions: Explain this method obtaining salts?

3.3. Pour some slaked lime powder Ca(OH) 2 into a test tube and add HCl solution.

Observations: Is there gas evolution?

Write the equation the reaction taking place (in molecular and ionic form).

Conclusion: 1. What type of reaction is the interaction between a hydroxide and an acid?

2.What substances are the products of this reaction?

3.5. Pour 1 ml of salt solutions into two test tubes: into the first - copper sulfate, into the second - cobalt chloride. Add to both test tubes drop by drop sodium hydroxide solution until precipitation forms. Then add excess alkali to both test tubes.

Observations: Indicate the changes in the color of precipitation in the reactions.

Write the equation the reaction taking place (in molecular and ionic form).

Conclusion: 1. As a result of what reactions are basic salts formed?

2. How can you convert basic salts to medium salts?

Test tasks:

1. From the listed substances, write down the formulas of salts, bases, acids: Ca(OH) 2, Ca(NO 3) 2, FeCl 3, HCl, H 2 O, ZnS, H 2 SO 4, CuSO 4, KOH
Zn(OH) 2, NH 3, Na 2 CO 3, K 3 PO 4.

2. Indicate the formulas of the oxides corresponding to the listed substances H 2 SO 4, H 3 AsO 3, Bi(OH) 3, H 2 MnO 4, Sn(OH) 2, KOH, H 3 PO 4, H 2 SiO 3, Ge( OH) 4 .

3. Which hydroxides are amphoteric? Write down reaction equations characterizing the amphotericity of aluminum hydroxide and zinc hydroxide.

4. Which of the following compounds will interact in pairs: P 2 O 5 , NaOH, ZnO, AgNO 3 , Na 2 CO 3 , Cr(OH) 3 , H 2 SO 4 . Write down equations for possible reactions.


Laboratory work No. 2 (4 hours)

Subject: Qualitative analysis of cations and anions

Target: master the technique of conducting qualitative and group reactions on cations and anions.

THEORETICAL PART

The main task of qualitative analysis is to establish chemical composition substances found in various objects ( biological materials, medicines, food products, objects environment). This paper examines a qualitative analysis inorganic substances, which are electrolytes, i.e. essentially a qualitative analysis of ions. From the entire set of occurring ions, the most important in medical and biological terms were selected: (Fe 3+, Fe 2+, Zn 2+, Ca 2+, Na +, K +, Mg 2+, Cl -, PO, CO, etc. ). Many of these ions are part of various medicines and food products.

In qualitative analysis, not all possible reactions are used, but only those that are accompanied by a clear analytical effect. The most common analytical effects: the appearance of a new color, the release of gas, the formation of a precipitate.

There are two fundamentally different approaches to qualitative analysis: fractional and systematic . In systematic analysis, group reagents are necessarily used to separate the ions present into separate groups, and in some cases into subgroups. To do this, some of the ions are converted into insoluble compounds, and some of the ions are left in solution. After separating the precipitate from the solution, they are analyzed separately.

For example, the solution contains A1 3+, Fe 3+ and Ni 2+ ions. If this solution is exposed to excess alkali, a precipitate of Fe(OH) 3 and Ni(OH) 2 precipitates, and [A1(OH) 4 ] - ions remain in the solution. The precipitate containing iron and nickel hydroxides will partially dissolve when treated with ammonia due to the transition to 2+ solution. Thus, using two reagents - alkali and ammonia, two solutions were obtained: one contained [A1(OH) 4 ] - ions, the other contained 2+ ions and a Fe(OH) 3 precipitate. Using characteristic reactions, the presence of certain ions in solutions and in the precipitate, which must first be dissolved, is then proven.

Systematic analysis is used mainly for the detection of ions in complex multicomponent mixtures. It is very labor-intensive, but its advantage lies in the easy formalization of all actions that fit into a clear scheme (methodology).

To carry out fractional analysis, only characteristic reactions are used. Obviously, the presence of other ions can significantly distort the results of the reaction (overlapping colors, unwanted precipitation, etc.). To avoid this, fractional analysis mainly uses highly specific reactions that give an analytical effect with a small number of ions. For successful reactions, it is very important to maintain certain conditions, in particular pH. Very often in fractional analysis it is necessary to resort to masking, that is, to convert ions into compounds that are not capable of producing an analytical effect with the selected reagent. For example, dimethylglyoxime is used to detect nickel ion. The Fe 2+ ion gives a similar analytical effect to this reagent. To detect Ni 2+, the Fe 2+ ion is transferred to a stable fluoride complex 4- or oxidized to Fe 3+, for example, with hydrogen peroxide.

Fractional analysis is used to detect ions in simpler mixtures. The analysis time is significantly reduced, but at the same time the experimenter is required to have a deeper knowledge of the patterns of chemical reactions, since all possible cases can be taken into account in one specific technique mutual influence ions on the nature of the observed analytical effects is quite difficult.

In analytical practice, the so-called fractional-systematic method. With this approach, a minimum number of group reagents is used, which makes it possible to outline analysis tactics in general outline, which is then carried out using the fractional method.

According to the technique of conducting analytical reactions, reactions are distinguished: sedimentary; microcrystalscopic; accompanied by the release of gaseous products; conducted on paper; extraction; colored in solutions; flame coloring.

When carrying out sedimentary reactions, be sure to note the color and nature of the sediment (crystalline, amorphous), and, if necessary, carry out additional tests: check the precipitate for solubility in strong and weak acids, alkalis and ammonia, and excess reagent. When carrying out reactions accompanied by the release of gas, its color and smell are noted. In some cases, additional tests are carried out.

For example, if the gas released is suspected to be carbon monoxide (IV), it is passed through an excess of lime water.

In fractional and systematic analyses, reactions during which a new color appears are widely used, most often these are complexation reactions or redox reactions.

In some cases, it is convenient to carry out such reactions on paper (droplet reactions). Reagents that do not decompose under normal conditions are applied to paper in advance. Thus, to detect hydrogen sulfide or sulfide ions, paper impregnated with lead nitrate is used [blackening occurs due to the formation of lead(II) sulfide]. Many oxidizing agents are detected using iodine starch paper, i.e. paper soaked in solutions of potassium iodide and starch. In most cases, the necessary reagents are applied to paper during the reaction, for example, alizarin for the A1 3+ ion, cupron for the Cu 2+ ion, etc. To enhance the color, extraction into an organic solvent is sometimes used. For preliminary tests, flame color reactions are used.

Classification of inorganic substances with examples of compounds

Now let's analyze the classification scheme presented above in more detail.

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

Simple substances These are substances that are formed by atoms of only one chemical element. For example, simple substances are hydrogen H2, oxygen O2, iron Fe, carbon C, etc.

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

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

Noble gases formed by chemical elements of group VIIIA.

Nonmetals are formed respectively by chemical elements located above the boron-astatine diagonal, with the exception of all elements of side 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 from. However, for many chemical elements the phenomenon of allotropy is widespread. Allotropy is the phenomenon when one chemical element capable of forming 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 are substances formed by atoms of two or more chemical elements.

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, there are 5 main classes, namely oxides, bases, amphoteric hydroxides, acids and salts:

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

The general formula of 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 (III) oxide; CuO—copper(II) oxide; N 2 O 5 - nitric oxide (V)

You can often find information that the valence of an element is indicated in parentheses, but this is not the case. So, for example, the oxidation state of nitrogen N 2 O 5 is +5, and the valence, 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 - zinc oxide.

Oxides classification

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

There are few non-salt-forming oxides; they are all formed by nonmetals 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 basic, acidic And amphoteric.

Basic oxides These are oxides that, when reacting with acids (or acid oxides), form salts. Basic oxides include metal oxides in the oxidation state +1 and +2, with the exception of the oxides BeO, ZnO, SnO, PbO.

Acidic oxides These are oxides that, when reacting with bases (or basic oxides), form salts. Acidic 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 are called oxides that 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 the oxidation states +3, +4, as well as the oxides BeO, ZnO, SnO, and PbO as exceptions.

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

As you can see, 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.

Grounds

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

Classification of bases

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

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

Bases are also divided into soluble (alkalis) and insoluble.

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

Nomenclature of bases

The name of the foundation is based on 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 whose molecules 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 the acidic residue.

For example, acids include compounds such as H2SO4, HCl, HNO3, HNO2, etc.

Classification of acids

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

- O base acids: HF, HCl, HBr, HI, HNO 3 ;

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

- T rehobasic 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 tetra- but monobasic. The basicity of organic acids is determined by the number of carboxyl groups (-COOH) in the molecule.

Also, based on the presence of oxygen in the molecules, acids are divided into oxygen-free (HF, HCl, HBr, etc.) and oxygen-containing (H 2 SO 4, HNO 3, H 3 PO 4, etc.). Oxygen-containing acids are also called oxoacids.

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 is a must-learn.

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

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

For example:

HF—hydrofluoric acid;

HCl—hydrochloric acid;

H 2 S is hydrosulfide acid.

The names of acidic residues of oxygen-free acids are based on the principle:

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

The names of oxygen-containing acids are obtained by adding the acid-forming element to the name various suffixes and endings. 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 acid hydroxides because they contain hydroxyl groups (OH). For example, this can be seen from the following graphical formulas of some oxygen-containing acids:

Thus, sulfuric acid can otherwise be called sulfur (VI) hydroxide, nitric acid - nitrogen (V) hydroxide, phosphoric acid - phosphorus (V) hydroxide, etc. In this case, the number in brackets characterizes the degree of oxidation of the acid-forming element. This version 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 tasks on the classification of inorganic substances.

Amphoteric hydroxides

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

Metal hydroxides in oxidation states +3 and +4 are amphoteric (as are oxides).

Also, as exceptions, amphoteric hydroxides include the compounds Be(OH) 2, Zn(OH) 2, Sn(OH) 2 and Pb(OH) 2, despite the oxidation state 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 Al(OH)3 or the meta form 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:

Salts

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

The definition presented above 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 - (methyl ammonium chloride), etc.

Classification of salts

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

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

Salts obtained by incomplete replacement of hydrogen cations in a dibasic (or more) acid with metal cations are called acidic. Thus, when hydrogen cations in sulfuric acid are incompletely replaced by sodium cations, the acid salt NaHSO 4 is formed.

Salts that are formed by incomplete replacement of hydroxide ions in two-acid (or more) bases are called bases. O strong salts. For example, when hydroxide ions in the base Ca(OH) 2 are incompletely replaced by nitrate ions, a base is formed O clear salt Ca(OH)NO3.

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

If a salt is formed by one type of cations 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 the replacement of hydrogen cations in acids with metal cations or products of the replacement of hydroxide ions in bases with anions of acidic residues. These are complex salts. For example, complex salts are sodium tetrahydroxozincate and tetrahydroxoaluminate with the formulas Na 2 and Na, respectively. Complex salts can most often be recognized among others by the presence of square brackets in the formula. However, you need to understand that in order for a substance to be classified as a salt, it must contain some cations other than (or instead of) H +, and the anions must contain some anions other than (or instead of) OH -. For example, the compound H2 does not belong to the class of complex salts, since when it dissociates from cations, only hydrogen cations H+ are present in the solution. Based on the type of dissociation, this substance should rather be classified as an oxygen-free complex acid. Likewise, the OH compound does not belong to salts, because this compound consists of cations + and hydroxide ions OH -, i.e. it should be considered a comprehensive foundation.

Nomenclature of salts

Nomenclature of medium and acid salts

The name of the middle and acid salts is built on the principle:

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

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

For example,

Na 2 SO 4 - sodium sulfate;

NaHSO 4 - sodium hydrogen sulfate;

CaCO 3 - calcium carbonate;

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

Nomenclature of basic salts

The names of the main salts are based on the principle:

For example:

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

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

Nomenclature of complex salts

The nomenclature of complex compounds is much more complicated, and to pass the Unified State Exam you do not need to know much about the nomenclature of complex salts.

You should be able to name complex salts obtained by reacting alkali solutions with amphoteric hydroxides. For example:

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

Trivial names of inorganic substances

By trivial names we mean the names of substances that are not related, or weakly related, to their composition and structure. Trivial names are determined, as a rule, either by historical reasons or by 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 potassium
NaOH caustic soda, caustic soda
H2O2 hydrogen peroxide
CuSO 4 ∙5H 2 O copper sulfate
NH4Cl ammonia
CaCO3 chalk, marble, limestone
N2O laughing gas
NO 2 brown gas
NaHCO3 baking (drinking) soda
Fe3O4 iron scale
NH 3 ∙H 2 O (NH 4 OH) ammonia
CO carbon monoxide
CO2 carbon dioxide
SiC carborundum (silicon carbide)
PH 3 phosphine
NH 3 ammonia
KClO3 Bertholet's salt (potassium chlorate)
(CuOH)2CO3 malachite
CaO quicklime
Ca(OH)2 slaked lime
transparent aqueous solution of Ca(OH) 2 lime water
suspension of solid Ca(OH) 2 in its aqueous solution lime milk
K2CO3 potash
Na 2 CO 3 soda ash
Na 2 CO 3 ∙10H 2 O crystal soda
MgO magnesia