DEFINITION

Iron- element of the eighth group of the fourth period of the Periodic Table of Chemical Elements by D. I. Mendeleev.

And the volume number is 26. The symbol is Fe (Latin “ferrum”). One of the most common metals in the earth's crust (second place after aluminum).

Physical properties of iron

Iron is a gray metal. In its pure form it is quite soft, malleable and viscous. The electronic configuration of the outer energy level is 3d 6 4s 2. In its compounds, iron exhibits oxidation states “+2” and “+3”. The melting point of iron is 1539C. Iron forms two crystalline modifications: α- and γ-iron. The first of them has a body-centered cubic lattice, the second has a face-centered cubic lattice. α-Iron is thermodynamically stable in two temperature ranges: below 912 and from 1394C to the melting point. Between 912 and 1394C γ-iron is stable.

The mechanical properties of iron depend on its purity - the content of even very small quantities of other elements in it. Solid iron has the ability to dissolve many elements in itself.

Chemical properties of iron

In humid air, iron quickly rusts, i.e. covered with a brown coating of hydrated iron oxide, which, due to its friability, does not protect iron from further oxidation. In water, iron corrodes intensely; with abundant access to oxygen, hydrate forms of iron (III) oxide are formed:

2Fe + 3/2O 2 + nH 2 O = Fe 2 O 3 ×H 2 O.

With a lack of oxygen or difficult access, mixed oxide (II, III) Fe 3 O 4 is formed:

3Fe + 4H 2 O (v) ↔ Fe 3 O 4 + 4H 2.

Iron dissolves in hydrochloric acid of any concentration:

Fe + 2HCl = FeCl 2 + H 2.

Dissolution in dilute sulfuric acid occurs similarly:

Fe + H 2 SO 4 = FeSO 4 + H 2.

In concentrated solutions of sulfuric acid, iron is oxidized to iron (III):

2Fe + 6H 2 SO 4 = Fe 2 (SO 4) 3 + 3SO 2 + 6H 2 O.

However, in sulfuric acid, the concentration of which is close to 100%, iron becomes passive and practically no interaction occurs. Iron dissolves in dilute and moderately concentrated solutions of nitric acid:

Fe + 4HNO 3 = Fe(NO 3) 3 + NO + 2H 2 O.

At high concentrations of nitric acid, dissolution slows down and iron becomes passive.

Like other metals, iron reacts with simple substances. Reactions between iron and halogens (regardless of the type of halogen) occur when heated. The interaction of iron with bromine occurs at increased vapor pressure of the latter:

2Fe + 3Cl 2 = 2FeCl 3;

3Fe + 4I 2 = Fe 3 I 8.

The interaction of iron with sulfur (powder), nitrogen and phosphorus also occurs when heated:

6Fe + N 2 = 2Fe 3 N;

2Fe + P = Fe 2 P;

3Fe + P = Fe 3 P.

Iron is capable of reacting with non-metals such as carbon and silicon:

3Fe + C = Fe 3 C;

Among the reactions of interaction of iron with complex substances, the following reactions play a special role - iron is capable of reducing metals that are in the activity series to the right of it from salt solutions (1), reducing iron (III) compounds (2):

Fe + CuSO 4 = FeSO 4 + Cu (1);

Fe + 2FeCl 3 = 3FeCl 2 (2).

Iron, at elevated pressure, reacts with a non-salt-forming oxide - CO with the formation of substances of complex composition - carbonyls - Fe (CO) 5, Fe 2 (CO) 9 and Fe 3 (CO) 12.

Iron, in the absence of impurities, is stable in water and in dilute alkali solutions.

Getting iron

The main method of obtaining iron is from iron ore (hematite, magnetite) or electrolysis of solutions of its salts (in this case, “pure” iron is obtained, i.e. iron without impurities).

Examples of problem solving

EXAMPLE 1

Exercise

Iron scale Fe 3 O 4 weighing 10 g was first treated with 150 ml of hydrochloric acid solution (density 1.1 g/ml) with a mass fraction of hydrogen chloride of 20%, and then excess iron was added to the resulting solution. Determine the composition of the solution (in % by weight).

Solution

Let us write the reaction equations according to the conditions of the problem: 8HCl + Fe 3 O 4 = FeCl 2 + 2FeCl 3 + 4H 2 O (1); 2FeCl 3 + Fe = 3FeCl 2 (2). Knowing the density and volume of a hydrochloric acid solution, you can find its mass: m sol (HCl) = V(HCl) × ρ (HCl); m sol (HCl) = 150×1.1 = 165 g. Let's calculate the mass of hydrogen chloride: m(HCl) = m sol (HCl) ×ω(HCl)/100%; m(HCl) = 165×20%/100% = 33 g. Molar mass (mass of one mole) of hydrochloric acid, calculated using the table of chemical elements by D.I. Mendeleev – 36.5 g/mol. Let's find the amount of hydrogen chloride: v(HCl) = m(HCl)/M(HCl); v(HCl) = 33/36.5 = 0.904 mol. Molar mass (mass of one mole) of scale, calculated using the table of chemical elements by D.I. Mendeleev – 232 g/mol. Let's find the amount of scale substance: v(Fe 3 O 4) = 10/232 = 0.043 mol. According to equation 1, v(HCl): v(Fe 3 O 4) = 1:8, therefore, v(HCl) = 8 v(Fe 3 O 4) = 0.344 mol. Then, the amount of hydrogen chloride calculated by the equation (0.344 mol) will be less than that indicated in the problem statement (0.904 mol). Therefore, hydrochloric acid is in excess and another reaction will occur: Fe + 2HCl = FeCl 2 + H 2 (3). Let us determine the amount of ferric chloride substance formed as a result of the first reaction (we use indices to denote a specific reaction): v 1 (FeCl 2):v(Fe 2 O 3) = 1:1 = 0.043 mol; v 1 (FeCl 3):v(Fe 2 O 3) = 2:1; v 1 (FeCl 3) = 2 × v (Fe 2 O 3) = 0.086 mol. Let us determine the amount of hydrogen chloride that did not react in reaction 1 and the amount of iron (II) chloride formed during reaction 3: v rem (HCl) = v(HCl) – v 1 (HCl) = 0.904 – 0.344 = 0.56 mol; v 3 (FeCl 2): ​​v rem (HCl) = 1:2; v 3 (FeCl 2) = 1/2 × v rem (HCl) = 0.28 mol. Let us determine the amount of FeCl 2 substance formed during reaction 2, the total amount of FeCl 2 substance and its mass: v 2 (FeCl 3) = v 1 (FeCl 3) = 0.086 mol; v 2 (FeCl 2): ​​v 2 (FeCl 3) = 3:2; v 2 (FeCl 2) = 3/2× v 2 (FeCl 3) = 0.129 mol; v sum (FeCl 2) = v 1 (FeCl 2) + v 2 (FeCl 2) + v 3 (FeCl 2) = 0.043 + 0.129 + 0.28 = 0.452 mol; m(FeCl 2) = v sum (FeCl 2) × M(FeCl 2) = 0.452 × 127 = 57.404 g. Let us determine the amount of substance and mass of iron that entered into reactions 2 and 3: v 2 (Fe): v 2 (FeCl 3) = 1:2; v 2 (Fe) = 1/2× v 2 (FeCl 3) = 0.043 mol; v 3 (Fe): v rem (HCl) = 1:2; v 3 (Fe) = 1/2×v rem (HCl) = 0.28 mol; v sum (Fe) = v 2 (Fe) + v 3 (Fe) = 0.043+0.28 = 0.323 mol; m(Fe) = v sum (Fe) ×M(Fe) = 0.323 ×56 = 18.088 g. Let's calculate the amount of substance and the mass of hydrogen released in reaction 3: v(H 2) = 1/2×v rem (HCl) = 0.28 mol; m(H 2) = v(H 2) ×M(H 2) = 0.28 × 2 = 0.56 g. We determine the mass of the resulting solution m’ sol and the mass fraction of FeCl 2 in it: m’ sol = m sol (HCl) + m(Fe 3 O 4) + m(Fe) – m(H 2);

Iron is the eighth element of the fourth period in the periodic table. Its number in the table (also called atomic) is 26, which corresponds to the number of protons in the nucleus and electrons in the electron shell. It is designated by the first two letters of its Latin equivalent - Fe (Latin Ferrum - read as “ferrum”). Iron is the second most common element in the earth's crust, the percentage is 4.65% (the most common is aluminum, Al). This metal is quite rare in its native form; more often it is mined from mixed ore with nickel.

In contact with

What is the nature of this connection? Iron as an atom consists of a metallic crystal lattice, which ensures the hardness of compounds containing this element and molecular stability. It is in connection with this that this metal is a typical solid, unlike, for example, mercury.

Iron as a simple substance- a silver-colored metal with properties typical for this group of elements: malleability, metallic luster and ductility. In addition, iron is highly reactive. The latter property is evidenced by the fact that iron corrodes very quickly in the presence of high temperature and corresponding humidity. In pure oxygen, this metal burns well, but if you crush it into very small particles, they will not only burn, but spontaneously ignite.

Often we do not call pure metal iron, but its alloys containing carbon, for example, steel (<2,14% C) и чугун (>2.14% C). Also of great industrial importance are alloys to which alloying metals (nickel, manganese, chromium and others) are added, due to which the steel becomes stainless, i.e. alloyed. Thus, based on this, it becomes clear what extensive industrial applications this metal has.

Characteristics of Fe

Chemical properties of iron

Let's take a closer look at the features of this element.

Properties of a simple substance

• Oxidation in air at high humidity (corrosive process):

4Fe+3O2+6H2O = 4Fe (OH)3 - iron (III) hydroxide (hydroxide)

• Combustion of iron wire in oxygen with the formation of a mixed oxide (it contains an element with both an oxidation state of +2 and an oxidation state of +3):

3Fe+2O2 = Fe3O4 (iron scale). The reaction is possible when heated to 160 ⁰C.

• Interaction with water at high temperatures (600−700 ⁰C):

3Fe+4H2O = Fe3O4+4H2

• Reactions with non-metals:

a) Reaction with halogens (Important! With this interaction, the oxidation state of the element becomes +3)

2Fe+3Cl2 = 2FeCl3 - ferric chloride

b) Reaction with sulfur (Important! With this interaction, the element has an oxidation state of +2)

Iron (III) sulfide - Fe2S3 can be obtained through another reaction:

Fe2O3+ 3H2S=Fe2S3+3H2O

c) Pyrite formation

Fe+2S = FeS2 - pyrite. Pay attention to the oxidation state of the elements that make up this compound: Fe (+2), S (-1).

• Interaction with metal salts located in the electrochemical series of metal activity to the right of Fe:

Fe+CuCl2 = FeCl2+Cu - iron (II) chloride

• Interaction with dilute acids (for example, hydrochloric and sulfuric):

Fe+HBr = FeBr2+H2

Fe+HCl = FeCl2+ H2

Please note that these reactions produce iron with an oxidation state of +2.

• In undiluted acids, which are strong oxidizing agents, the reaction is possible only when heated; in cold acids the metal is passivated:

Fe+H2SO4 (concentrated) = Fe2 (SO4)3+3SO2+6H2O

Fe+6HNO3 = Fe (NO3)3+3NO2+3H2O

• The amphoteric properties of iron appear only when interacting with concentrated alkalis:

Fe+2KOH+2H2O = K2+H2 - potassium tetrahydroxyferrate (II) precipitates.

The process of producing cast iron in a blast furnace

• Roasting and subsequent decomposition of sulfide and carbonate ores (release of metal oxides):

FeS2 —> Fe2O3 (O2, 850 ⁰C, -SO2). This reaction is also the first step in the industrial synthesis of sulfuric acid.

FeCO3 —> Fe2O3 (O2, 550−600 ⁰C, -CO2).

• Burning coke (in excess):

C (coke)+O2 (air) —> CO2 (600−700 ⁰C)

CO2+С (coke) —> 2CO (750−1000 ⁰C)

• Reduction of ore containing oxide with carbon monoxide:

Fe2O3 —> Fe3O4 (CO, -CO2)

Fe3O4 —> FeO (CO, -CO2)

FeO —> Fe (CO, -CO2)

• Carburization of iron (up to 6.7%) and melting of cast iron (melting temperature - 1145 ⁰C)

Fe (solid) + C (coke) -> cast iron. Reaction temperature - 900−1200 ⁰C.

Cast iron always contains cementite (Fe2C) and graphite in the form of grains.

Characteristics of compounds containing Fe

Let's study the features of each connection separately.

Fe3O4

Mixed or double iron oxide, containing an element with an oxidation state of both +2 and +3. Also called Fe3O4 iron oxide. This compound withstands high temperatures. Does not react with water or water vapor. Subject to decomposition by mineral acids. Can be reduced with hydrogen or iron at high temperatures. As you can understand from the above information, it is an intermediate product in the reaction chain of industrial cast iron production.

Iron scale is directly used in the production of mineral-based paints, colored cement and ceramic products. Fe3O4 is what is obtained when steel is blackened and blued. A mixed oxide is obtained by burning iron in air (the reaction is given above). The ore containing oxides is magnetite.

Fe2O3

Iron (III) oxide, trivial name - hematite, a red-brown compound. Resistant to high temperatures. It is not formed in its pure form by the oxidation of iron with atmospheric oxygen. Does not react with water, forms hydrates that precipitate. Reacts poorly with dilute alkalis and acids. It can alloy with oxides of other metals, forming spinels - double oxides.

Red iron ore is used as a raw material in the industrial production of cast iron using the blast furnace method. It also accelerates the reaction, that is, it acts as a catalyst, in the ammonia industry. Used in the same areas as iron oxide. Plus, it was used as a carrier of sound and pictures on magnetic tapes.

FeOH2

Iron(II) hydroxide, a compound that has both acidic and basic properties, the latter predominating, that is, it is amphoteric. A white substance that quickly oxidizes in air and “turns brown” to iron (III) hydroxide. Subject to decomposition when exposed to temperature. It reacts with both weak solutions of acids and alkalis. We will not dissolve in water. In the reaction it acts as a reducing agent. It is an intermediate product in the corrosion reaction.

Detection of Fe2+ and Fe3+ ions (“qualitative” reactions)

Recognition of Fe2+ and Fe3+ ions in aqueous solutions is carried out using complex complex compounds - K3, red blood salt, and K4, yellow blood salt, respectively. In both reactions, a rich blue precipitate is formed with the same quantitative composition, but a different position of iron with valency +2 and +3. This precipitate is also often called Prussian blue or Turnbull blue.

Reaction written in ionic form

Fe2++K++3-  K+1Fe+2

Fe3++K++4-  K+1Fe+3

A good reagent for detecting Fe3+ is thiocyanate ion (NCS-)

Fe3++ NCS-  3- - these compounds have a bright red (“bloody”) color.

This reagent, for example, potassium thiocyanate (formula - KNCS), allows you to determine even negligible concentrations of iron in solutions. Thus, when examining tap water, he is able to determine whether the pipes are rusty.

Fe 2 (SO 4) 3 Mol. V. 399.88

Fe 2 (SO 4) 3 9H 2 O Mol. V. 562.02

Properties

The anhydrous reagent is a white or yellowish powder that dissolves in air into a brown liquid. Pl. 3.097 g/cm3.

Crystalline hydrate Fe 2 (SO 4) 3 9H 2 O - crystalline substance, pl. 2.1 g/cm3. Salt is capable of forming very concentrated aqueous solutions (at 20 °C, 440 g of Fe 2 (SO 4) 3 9H 2 O are dissolved in 100 g of water), but dissolution is slow; soluble in ethyl alcohol, insoluble in concentrated H 2 SO 4. The aqueous solution due to hydrolysis (formation of Fe(OH) 3 sol) is colored red-brown; the addition of H 2 SO 4 suppresses hydrolysis and the solution becomes almost colorless. When a dilute solution is boiled, the basic salt precipitates.

Preparation

1. Iron (III) sulfate can be obtained by dissolving iron (III) hydroxide in sulfuric acid:

Fe(NO 3) 3 + 3NH 4 OH = 3NH 4 NO 3 + Fe(OH) 3 c

2Fe(OH) 3 + 3H 2 SO 4 = Fe 2 (SO 4) 3 + 6H 2 O

65-70 ml of NH 4 OH (analytical grade or analytical grade, pl. 0.91) is added to a solution of 50 g of Fe(NO) 3 ·9H 2 O (pure grade) in 50 ml of hot water. The Fe(OH) 3 precipitate is quickly washed by decantation with hot water until there is complete absence of NO 3 - in the wash water (test with diphenylamine).

The wet Fe(OH) 3 precipitate is transferred to a porcelain cup, 9 ml of H 2 SO 4 (reagent grade, pl. 1.84) is added and heated for 1-2 hours, stirring frequently, until the precipitate is almost completely dissolved. The solution is filtered, 1 drop of H 2 SO 4 is added to the filtrate and evaporated to the consistency of a thick syrup (the volume of the remaining liquid should be about 50 ml). A seed (crystal of Fe 2 (SO 4) 3 ·9H 2 O) is added to the solution and left for a day for crystallization. The crystals are sucked off using a Buchner funnel and dried on a glass plate at 50-60 °C.

Yield 40 g (80%). The resulting preparation usually corresponds to an analytical grade reagent.

2. A preparation of the same purity can be obtained by oxidation of iron (II) sulfate with nitric acid:

2FeSO 4 + H 2 SO 4 + 2HNO 3 = Fe 2 (SO 4) 3 + 2NO 2 b + 2H 2 O

Work should be carried out under traction.

8 ml of H2SO4 (analytical grade, pl. 1.84) is added in small portions to a solution of 85 g of FeSO 4 7H 2 O (analytical grade) in 110 ml of water heated to 70 °C ( beware of splashes!) and then 100 ml of HNO 3 (analytical grade, pl. 1.35), maintaining the solution temperature at 95-100 °C. The degree of oxidation of Fe 2+ in Fe 3+ is checked by a test with K 3 (Fe(CN) 6) (with complete oxidation there should be no blue coloration).

The solution is filtered, 4 ml of H 2 SO 4 is added to the filtrate and evaporated until a viscous dough-like mass is formed, and its temperature reaches 120 ° C. The mass is cooled to 45-50 °C, the precipitated crystals are sucked off using a Buchner funnel and dried at a temperature not exceeding 65 °C.

Length and distance converter Mass converter Converter of volume measures of bulk products and food products Area converter Converter of volume and units of measurement in culinary recipes Temperature converter Converter of pressure, mechanical stress, Young's modulus Converter of energy and work Converter of power Converter of force Converter of time Linear speed converter Flat angle Converter thermal efficiency and fuel efficiency Converter of numbers in various number systems Converter of units of measurement of quantity of information Currency rates Women's clothing and shoe sizes Men's clothing and shoe sizes Angular velocity and rotation frequency converter Acceleration converter Angular acceleration converter Density converter Specific volume converter Moment of inertia converter Moment of force converter Torque converter Specific heat of combustion converter (by mass) Energy density and specific heat of combustion converter (by volume) Temperature difference converter Coefficient of thermal expansion converter Thermal resistance converter Thermal conductivity converter Specific heat capacity converter Energy exposure and thermal radiation power converter Heat flux density converter Heat transfer coefficient converter Volume flow rate converter Mass flow rate converter Molar flow rate converter Mass flow density converter Molar concentration converter Mass concentration in solution converter Dynamic (absolute) viscosity converter Kinematic viscosity converter Surface tension converter Vapor permeability converter Water vapor flow density converter Sound level converter Microphone sensitivity converter Converter Sound Pressure Level (SPL) Sound Pressure Level Converter with Selectable Reference Pressure Luminance Converter Luminous Intensity Converter Illuminance Converter Computer Graphics Resolution Converter Frequency and Wavelength Converter Diopter Power and Focal Length Diopter Power and Lens Magnification (×) Converter electric charge Linear charge density converter Surface charge density converter Volume charge density converter Electric current converter Linear current density converter Surface current density converter Electric field strength converter Electrostatic potential and voltage converter Electrical resistance converter Electrical resistivity converter Electrical conductivity converter Electrical conductivity converter Electrical capacitance Inductance Converter American Wire Gauge Converter Levels in dBm (dBm or dBm), dBV (dBV), watts, etc. units Magnetomotive force converter Magnetic field strength converter Magnetic flux converter Magnetic induction converter Radiation. Ionizing radiation absorbed dose rate converter Radioactivity. Radioactive decay converter Radiation. Exposure dose converter Radiation. Absorbed dose converter Decimal prefix converter Data transfer Typography and image processing unit converter Timber volume unit converter Calculation of molar mass Periodic table of chemical elements by D. I. Mendeleev

Chemical formula

Molar mass of Fe 2 (SO 4) 3, iron (III) sulfate 399.8778 g/mol

55.845 2+(32.065+15.9994 4) 3

Mass fractions of elements in the compound

Using the Molar Mass Calculator

• Chemical formulas must be entered case sensitive
• Subscripts are entered as regular numbers
• The dot on the midline (multiplication sign), used, for example, in the formulas of crystalline hydrates, is replaced by a regular dot.
• Example: instead of CuSO₄·5H₂O in the converter, for ease of entry, the spelling CuSO4.5H2O is used.

Molar mass calculator

Mole

All substances are made up of atoms and molecules. In chemistry, it is important to accurately measure the mass of substances that react and are produced as a result. By definition, the mole is the SI unit of quantity of a substance. One mole contains exactly 6.02214076×10²³ elementary particles. This value is numerically equal to Avogadro's constant N A when expressed in units of mol⁻¹ and is called Avogadro's number. Amount of substance (symbol n) of a system is a measure of the number of structural elements. A structural element can be an atom, molecule, ion, electron, or any particle or group of particles.

Avogadro's constant N A = 6.02214076×10²³ mol⁻¹. Avogadro's number is 6.02214076×10²³.

In other words, a mole is an amount of substance equal in mass to the sum of the atomic masses of atoms and molecules of the substance, multiplied by Avogadro's number. The unit of quantity of a substance, the mole, is one of the seven basic SI units and is symbolized by the mole. Since the name of the unit and its symbol are the same, it should be noted that the symbol is not declined, unlike the name of the unit, which can be declined according to the usual rules of the Russian language. One mole of pure carbon-12 is equal to exactly 12 g.

Molar mass

Molar mass is a physical property of a substance, defined as the ratio of the mass of this substance to the amount of substance in moles. In other words, this is the mass of one mole of a substance. The SI unit of molar mass is kilogram/mol (kg/mol). However, chemists are accustomed to using the more convenient unit g/mol.

molar mass = g/mol

Molar mass of elements and compounds

Compounds are substances consisting of different atoms that are chemically bonded to each other. For example, the following substances, which can be found in any housewife’s kitchen, are chemical compounds:

• salt (sodium chloride) NaCl
• sugar (sucrose) C₁₂H₂₂O₁₁
• vinegar (acetic acid solution) CH₃COOH

The molar mass of a chemical element in grams per mole is numerically the same as the mass of the element's atoms expressed in atomic mass units (or daltons). The molar mass of compounds is equal to the sum of the molar masses of the elements that make up the compound, taking into account the number of atoms in the compound. For example, the molar mass of water (H₂O) is approximately 1 × 2 + 16 = 18 g/mol.

Molecular mass

Molecular mass (the old name is molecular weight) is the mass of a molecule, calculated as the sum of the masses of each atom that makes up the molecule, multiplied by the number of atoms in this molecule. Molecular weight is dimensionless a physical quantity numerically equal to molar mass. That is, molecular mass differs from molar mass in dimension. Although molecular mass is dimensionless, it still has a value called the atomic mass unit (amu) or dalton (Da), which is approximately equal to the mass of one proton or neutron. The atomic mass unit is also numerically equal to 1 g/mol.

Calculation of molar mass

Molar mass is calculated as follows:

• determine the atomic masses of elements according to the periodic table;
• determine the number of atoms of each element in the compound formula;
• determine the molar mass by adding the atomic masses of the elements included in the compound, multiplied by their number.

For example, let's calculate the molar mass of acetic acid

It consists of:

• two carbon atoms
• four hydrogen atoms
• two oxygen atoms

• carbon C = 2 × 12.0107 g/mol = 24.0214 g/mol
• hydrogen H = 4 × 1.00794 g/mol = 4.03176 g/mol
• oxygen O = 2 × 15.9994 g/mol = 31.9988 g/mol
• molar mass = 24.0214 + 4.03176 + 31.9988 = 60.05196 g/mol

Our calculator performs exactly this calculation. You can enter the acetic acid formula into it and check what happens.

Do you find it difficult to translate units of measurement from one language to another? Colleagues are ready to help you. Post a question in TCTerms and within a few minutes you will receive an answer.

Iron(II) compounds

Iron compounds with the oxidation state of iron +2 are unstable and are easily oxidized to iron (III) derivatives.

Fe 2 O 3 + CO = 2FeO + CO 2.

Iron (II) hydroxide Fe(OH) 2 when freshly precipitated, it has a grayish-green color, does not dissolve in water, decomposes at temperatures above 150 ° C, and quickly darkens due to oxidation:

4Fe(OH) 2 + O 2 + 2H 2 O = 4Fe(OH) 3.

It exhibits mild amphoteric properties with a predominance of basic ones, and easily reacts with non-oxidizing acids:

Fe(OH) 2 + 2HCl = FeCl 2 + 2H 2 O.

Reacts with concentrated alkali solutions when heated to form tetrahydroxoferrate (II):

Fe(OH) 2 + 2NaOH = Na 2.

It exhibits reducing properties; when interacting with nitric or concentrated sulfuric acid, iron (III) salts are formed:

2Fe(OH) 2 + 4H 2 SO 4 = Fe 2 (SO 4) 3 + SO 2 + 6H 2 O.

It is obtained by reacting iron (II) salts with an alkali solution in the absence of atmospheric oxygen:

FeSO 4 + 2NaOH = Fe(OH) 2 + Na 2 SO 4.

Iron (II) salts. Iron (II) forms salts with almost all anions. Typically, salts crystallize in the form of green crystalline hydrates: Fe(NO 3) 2 6H 2 O, FeSO 4 7H 2 O, FeBr 2 6H 2 O, (NH 4) 2 Fe(SO 4) 2 6H 2 O (salt Mora), etc. Salt solutions have a pale green color and, due to hydrolysis, an acidic environment:

Fe 2+ + H 2 O = FeOH + + H +.

They exhibit all the properties of salts.

When standing in air, they are slowly oxidized by dissolved oxygen to iron (III) salts:

4FeCl 2 + O 2 + 2H 2 O = 4FeOHCl 2.

Qualitative reaction to the Fe 2+ cation - interaction with potassium hexacyanoferrate (III) (red blood salt):

FeSO 4 + K 3 = KFe↓ + K 2 SO 4

Fe 2+ + K + + 3- = KFe↓

As a result of the reaction, a blue precipitate is formed - iron (III) - potassium hexacyanoferrate (II).

The oxidation state +3 is characteristic of iron.

Iron (III) oxide Fe 2 O 3 - The substance is brown in color and exists in three polymorphic modifications.

Shows mild amphoteric properties with a predominance of basic ones. Reacts easily with acids:

Fe 2 O 3 + 6HCl = 2FeCl 3 + 3H 2 O.

It does not react with alkali solutions, but upon fusion it forms ferrites:

Fe 2 O 3 + 2NaOH = 2NaFeO 2 + H 2 O.

Shows oxidizing and reducing properties. When heated, it is reduced by hydrogen or carbon monoxide (II), exhibiting oxidizing properties:

Fe 2 O 3 + H 2 = 2FeO + H 2 O,

Fe 2 O 3 + CO = 2FeO + CO 2.

In the presence of strong oxidizing agents in an alkaline environment, it exhibits reducing properties and is oxidized to iron (VI) derivatives:

Fe 2 O 3 + 3KNO 3 + 4KOH = 2K 2 FeO 4 + 3KNO 2 + 2H 2 O.

At temperatures above 1400°C it decomposes:

6Fe 2 O 3 = 4Fe 3 O 4 + O 2.

Obtained by thermal decomposition of iron (III) hydroxide:

2Fe(OH) 3 = Fe 2 O 3 + 3H 2 O

or pyrite oxidation:

4FeS 2 + 11O 2 = 2Fe 2 O 3 + 8SO 2.

FeCl 3 + 3KCNS = Fe(CNS) 3 + 3KCl,