It is one of the most common elements in the earth's crust.

Physical properties of iron.

Iron- malleable silver-white metal with high chemical resistance. It tolerates high temperatures and humidity well. It quickly tarnishes (rusts) in air and in water. Very plastic, well gives in to forging and rolling. It has good thermal and electrical conductivity, an excellent ferromagnet.

Chemical properties of iron.

Iron transition metal. It can have an oxidation state of +2 and +3. Reacts with water vapor:

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

But in the presence of moisture, iron rusts:

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

2 Fe + 3 Cl 2 = 2 FeCl 3 .

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

Concentrated acids passivate iron in the cold, but dissolve when heated:

2Fe + 6H 2 SO 4 \u003d Fe 2 (SO 4) 3 + 3SO 2 + 6H 2 O.

Iron hydroxide (II) obtained by the action of alkali on salts of iron (II) without access to oxygen:

F 2 SO 4 + 2NaOH \u003d Fe (OH) 2 + Na 2 SO 4.

A white precipitate is formed, which quickly oxidizes in air:

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

This hydroxide is amphoteric; when heated, it dissolves in alkalis with the formation of hexahydroferate:

Fe (OH) 3 + 3KOH \u003d K 3.

Iron forms two complex iron salts:

• yellow blood salt K 4 [ Fe(CN) 6 ];
• red blood salt K 3 [ Fe(CN) 6 ].

These compounds are qualitative for the determination of iron ions. Compound Prussian blue:

K 4 + Fe 2+ \u003d KFe III + 2K +.

The use of iron.

Iron is an essential component of the respiration process. It is part of the hemoglobin of the blood, is involved in the transfer of oxygen from the lungs to the tissues. In nature, iron is found in the composition of ores and minerals.

DEFINITION

Iron- an element of the fourth period of group VIII of the secondary (B) subgroup of the Periodic Table. Designation - Fe. In the form of a simple substance, iron is a silvery-white metal.

The density is 7.87 g/cm 3 . Melting point 1539 o C, boiling point 3200 o C. Iron has several modifications. Up to 769 o With stable α-iron with a body-centered cubic lattice and ferromagnetic properties. At 769 o With the transition to β-iron (the same crystal structure, paramagnetic). At 910 o With formed γ-iron with a face-centered crystal lattice. paramagnetic properties. At 1400 o C and up to the melting temperature - δ- iron with a body-centered cubic lattice.

The oxidation state of iron in compounds

Iron can exist in the form of a simple substance - a metal, and the oxidation state of metals in the elemental state is zero, since the distribution of electron density in them is uniform.

Iron has oxidation states (+2) and (+3) : Fe +2 O, Fe +3 2 O 3, Fe +2 (OH) 2, Fe +3 (OH) 3, Fe +2 Cl 2, Fe +3 Cl 3, Fe +2 SO 4, Fe +3 2 (SO 4) 3 .

Known iron compounds with oxidation state (+6) , they are called "ferrates" (K 2 Fe +6 O 4).

Examples of problem solving

EXAMPLE 1

EXAMPLE 2

Iron(II) compounds

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

Fe 2 O 3 + CO \u003d 2FeO + CO 2.

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

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

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

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

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

Fe (OH) 2 + 2NaOH \u003d 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 the interaction of iron (II) salts with an alkali solution in the absence of atmospheric oxygen:

FeSO 4 + 2NaOH \u003d Fe (OH) 2 + Na 2 SO 4.

Salts of iron (II). Iron (II) forms salts with almost all anions. Usually 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 Mohr) and others. Salt solutions have a pale green color and, due to hydrolysis, an acidic environment:

Fe 2+ + H 2 O \u003d FeOH + + H +.

Show 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 \u003d 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) hexacyanoferrate (II) - potassium.

The +3 oxidation state is characteristic of iron.

Iron oxide (III) Fe 2 O 3 - substance of brown color, exists in three polymorphic modifications.

It exhibits weakly expressed amphoteric properties with a predominance of basic ones. Easily reacts with acids:

Fe 2 O 3 + 6HCl \u003d 2FeCl 3 + 3H 2 O.

It does not react with alkali solutions, but forms ferrites when fused:

Fe 2 O 3 + 2NaOH \u003d 2NaFeO 2 + H 2 O.

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

Fe 2 O 3 + H 2 \u003d 2FeO + H 2 O,

Fe 2 O 3 + CO \u003d 2FeO + CO 2.

In the presence of strong oxidizing agents in an alkaline medium, 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 decomposes:

6Fe 2 O 3 \u003d 4Fe 3 O 4 + O 2.

It is obtained by thermal decomposition of iron (III) hydroxide:

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

or oxidation of pyrite:

4FeS 2 + 11O 2 \u003d 2Fe 2 O 3 + 8SO 2.

FeCl 3 + 3KCNS \u003d Fe (CNS) 3 + 3KCl,

68. Iron compounds

Iron(II) oxide FeO- a black crystalline substance, insoluble in water and alkalis. FeO matches base Fe(OH)2.

Receipt. Iron oxide (II) can be obtained by incomplete reduction of magnetic iron ore with carbon monoxide (II):

Chemical properties. It is the main oxide. Reacts with acids to form salts:

Iron(II) hydroxide Fe(OH)2- white crystalline substance.

Receipt. Iron (II) hydroxide is obtained from ferrous salts by the action of alkali solutions:

Chemical properties. basic hydroxide. Reacts with acids:

In air, Fe (OH) 2 is oxidized to Fe (OH) 3:

Iron(III) oxide Fe2O3- a brown substance, occurs in nature in the form of red iron ore, insoluble in water.

Receipt. When firing pyrite:

Chemical properties. Shows weak amphoteric properties. When interacting with alkalis, it forms salts:

Iron(III) hydroxide Fe(OH)3- a substance of red-brown color, insoluble in water and excess alkali.

Receipt. Obtained by oxidation of iron oxide (III) and iron hydroxide (II).

Chemical properties. It is an amphoteric compound (with a predominance of basic properties). It precipitates under the action of alkalis on ferric salts:

Ferrous salts obtained by the interaction of metallic iron with the corresponding acids. They are strongly hydrolyzed, therefore their aqueous solutions are energetic reducing agents:

When heated above 480 °C, it decomposes, forming oxides:

Under the action of alkalis on iron (II) sulfate, iron (II) hydroxide is formed:

Forms a crystalline hydrate FeSO4?7H2O (iron vitriol). Iron (III) chloride FeCl3 – dark brown crystalline substance.

Chemical properties. Soluble in water. FeCl3 exhibits oxidizing properties.

Reducing agents - magnesium, zinc, hydrogen sulfide, are oxidized without heating.

Iron is a chemical element

1. The position of iron in the periodic table of chemical elements and the structure of its atom

Iron is a d-element of group VIII; serial number - 26; atomic mass Ar (Fe ) = 56; atom composition: 26-protons; 30 - neutrons; 26 - electrons.

Scheme of the structure of the atom:

Electronic formula: 1s 2 2s 2 2p 6 3s 2 3p 6 3d 6 4s 2

Medium activity metal, reducing agent:

Fe 0 -2 e - → Fe +2 , the reducing agent is oxidized

Fe 0 -3 e - → Fe +3 , the reducing agent is oxidized

Main oxidation states: +2, +3

2. Prevalence of iron

Iron is one of the most abundant elements in nature. . In the earth's crust, its mass fraction is 5.1%, according to this indicator, it second only to oxygen, silicon and aluminum. A lot of iron is also found in celestial bodies, which is established from the data of spectral analysis. In samples of lunar soil, which were delivered by the automatic station "Luna", iron was found in an unoxidized state.

Iron ores are quite widespread on Earth. The names of the mountains in the Urals speak for themselves: High, Magnetic, Iron. Agricultural chemists find iron compounds in soils.

Iron is found in most rocks. To obtain iron, iron ores with an iron content of 30-70% or more are used.

The main iron ores are :

magnetite(magnetic iron ore) - Fe 3 O 4 contains 72% iron, deposits are found in the Southern Urals, the Kursk magnetic anomaly:

hematite(iron sheen, bloodstone) - Fe2O3 contains up to 65% iron, such deposits are found in the Krivoy Rog region:

limonite(brown iron ore) - Fe 2 O 3 * nH 2 O contains up to 60% iron, deposits are found in the Crimea:

pyrite(sulfur pyrite, iron pyrite, cat's gold) - FeS 2 contains approximately 47% iron, deposits are found in the Urals.

3. The role of iron in human and plant life

Biochemists have discovered the important role of iron in the life of plants, animals and humans. Being part of an extremely complex organic compound called hemoglobin, iron determines the red color of this substance, which in turn determines the color of the blood of humans and animals. The body of an adult contains 3 g of pure iron, 75% of which is part of hemoglobin. The main role of hemoglobin is the transfer of oxygen from the lungs to the tissues, and in the opposite direction - CO 2.

Plants also need iron. It is part of the cytoplasm, participates in the process of photosynthesis. Plants grown on an iron-free substrate have white leaves. A small addition of iron to the substrate - and they turn green. Moreover, it is worth smearing a white sheet with a solution of salt containing iron, and soon the smeared place turns green.

So from the same reason - the presence of iron in juices and tissues - the leaves of plants turn green cheerfully and the cheeks of a person blush brightly.

4. Physical properties of iron.

Iron is a silvery-white metal with a melting point of 1539 o C. It is very ductile, therefore it is easily processed, forged, rolled, stamped. Iron has the ability to be magnetized and demagnetized, therefore it is used as the cores of electromagnets in various electrical machines and apparatuses. It can be given greater strength and hardness by methods of thermal and mechanical action, for example, by quenching and rolling.

There are chemically pure and technically pure iron. Technically pure iron, in fact, is a low-carbon steel, it contains 0.02 -0.04% carbon, and even less oxygen, sulfur, nitrogen and phosphorus. Chemically pure iron contains less than 0.01% impurities. chemically pure iron silvery-gray, shiny, in appearance very similar to platinum metal. Chemically pure iron is resistant to corrosion and well resists the action of acids. However, insignificant fractions of impurities deprive it of these precious properties.

5. Obtaining iron

Recovery from oxides with carbon or carbon monoxide (II), as well as hydrogen:

FeO + C = Fe + CO

Fe 2 O 3 + 3CO \u003d 2Fe + 3CO 2

Fe 2 O 3 + 3H 2 \u003d 2Fe + 3H 2 O

Experience "Obtaining iron by aluminothermy"

6. Chemical properties of iron

As an element of a side subgroup, iron can exhibit several oxidation states. We will consider only compounds in which iron exhibits oxidation states +2 and +3. Thus, we can say that iron has two series of compounds in which it is divalent and trivalent.

1) In air, iron is easily oxidized in the presence of moisture (rusting):

4Fe + 3O 2 + 6H 2 O \u003d 4Fe (OH) 3

2) A heated iron wire burns in oxygen, forming scale - iron oxide (II, III) - a black substance:

3Fe + 2O 2 = Fe 3 O 4

Coxygen in moist air forms Fe 2 O 3 * nH 2 O

Experience "Interaction of iron with oxygen"

3) At high temperatures (700–900°C), iron reacts with water vapor:

3Fe + 4H 2 O t˚C → Fe 3 O 4 + 4H 2

4) Iron reacts with non-metals when heated:

Fe + S t˚C → FeS

5) Iron readily dissolves in hydrochloric and dilute sulfuric acids under normal conditions:

Fe + 2HCl \u003d FeCl 2 + H 2

Fe + H 2 SO 4 (diff.) \u003d FeSO 4 + H 2

6) In concentrated acids - oxidizing agents, iron dissolves only when heated

2Fe + 6H 2 SO 4 (conc .) t˚C → Fe 2 (SO 4) 3 + 3SO 2 + 6H 2 O

Fe + 6HNO 3 (conc .) t˚C → Fe(NO 3) 3 + 3NO 2 + 3H 2 OIron(III)

7. The use of iron.

The main part of the iron produced in the world is used to produce iron and steel - iron alloys with carbon and other metals. Cast irons contain about 4% carbon. Steels contain less than 1.4% carbon.

Cast iron is needed for the production of various castings - the beds of heavy machines, etc.

Cast iron products

Steels are used for the manufacture of machines, various building materials, beams, sheets, rolled products, rails, tools and many other products. For the production of various grades of steel, the so-called alloying additives are used, which are various metals: M

Simulator №2 - Fe 3+ Genetic Series

Simulator No. 3 - Equations for the reactions of iron with simple and complex substances

Tasks for fixing

No. 1. Make up the equations for the reactions of obtaining iron from its oxides Fe 2 O 3 and Fe 3 O 4 using as a reducing agent:
a) hydrogen;
b) aluminum;
c) carbon monoxide (II).
For each reaction, make an electronic balance.

No. 2. Carry out the transformations according to the scheme:
Fe 2 O 3 -> Fe - + H2O, t -> X - + CO, t -> Y - + HCl -> Z
Name the products X, Y, Z?