The human body contains about 5 g of iron, most of it (70%) is part of the hemoglobin in the blood.
Physical Properties
In the free state, iron is a silvery-white metal with a grayish tinge. Pure iron is ductile and has ferromagnetic properties. In practice, iron alloys are commonly used - cast irons and steels.
Fe is the most important and most common element of the nine d-metals of the secondary subgroup of group VIII. Together with cobalt and nickel, it forms the "iron family".
When forming compounds with other elements, it often uses 2 or 3 electrons (B \u003d II, III).
Iron, like almost all d-elements of group VIII, does not show a higher valence equal to the group number. Its maximum valency reaches VI and is extremely rare.
The most typical compounds are those in which the Fe atoms are in the +2 and +3 oxidation states.
Methods for obtaining iron
1. Commercial iron (in an alloy with carbon and other impurities) is obtained by carbothermal reduction of its natural compounds according to the scheme:
Recovery occurs gradually, in 3 stages:
1) 3Fe 2 O 3 + CO = 2Fe 3 O 4 + CO 2
2) Fe 3 O 4 + CO = 3FeO + CO 2
3) FeO + CO \u003d Fe + CO 2
The cast iron resulting from this process contains more than 2% carbon. In the future, steels are obtained from cast iron - iron alloys containing less than 1.5% carbon.
2. Very pure iron is obtained in one of the following ways:
a) decomposition of pentacarbonyl Fe
Fe(CO) 5 \u003d Fe + 5CO
b) hydrogen reduction of pure FeO
FeO + H 2 \u003d Fe + H 2 O
c) electrolysis of aqueous solutions of Fe +2 salts
FeC 2 O 4 \u003d Fe + 2СO 2
iron(II) oxalate
Chemical properties
Fe - a metal of medium activity, exhibits general properties characteristic of metals.
A unique feature is the ability to "rust" in humid air:
In the absence of moisture with dry air, iron begins to noticeably react only at T > 150°C; when calcined, “iron scale” Fe 3 O 4 is formed:
3Fe + 2O 2 = Fe 3 O 4
Iron does not dissolve in water in the absence of oxygen. At very high temperatures, Fe reacts with water vapor, displacing hydrogen from water molecules:
3 Fe + 4H 2 O (g) \u003d 4H 2
The rusting process in its mechanism is electrochemical corrosion. The rust product is presented in a simplified form. In fact, a loose layer of a mixture of oxides and hydroxides of variable composition is formed. Unlike the Al 2 O 3 film, this layer does not protect the iron from further destruction.
Types of corrosion
Corrosion protection of iron
1. Interaction with halogens and sulfur at high temperature.
2Fe + 3Cl 2 = 2FeCl 3
2Fe + 3F 2 = 2FeF 3
Fe + I 2 \u003d FeI 2
Compounds are formed in which the ionic type of bond predominates.
2. Interaction with phosphorus, carbon, silicon (iron does not directly combine with N 2 and H 2, but dissolves them).
Fe + P \u003d Fe x P y
Fe + C = Fe x C y
Fe + Si = FexSiy
Substances of variable composition are formed, since berthollides (the covalent nature of the bond prevails in the compounds)
3. Interaction with "non-oxidizing" acids (HCl, H 2 SO 4 dil.)
Fe 0 + 2H + → Fe 2+ + H 2
Since Fe is located in the activity series to the left of hydrogen (E ° Fe / Fe 2+ \u003d -0.44V), it is able to displace H 2 from ordinary acids.
Fe + 2HCl \u003d FeCl 2 + H 2
Fe + H 2 SO 4 \u003d FeSO 4 + H 2
4. Interaction with "oxidizing" acids (HNO 3 , H 2 SO 4 conc.)
Fe 0 - 3e - → Fe 3+
Concentrated HNO 3 and H 2 SO 4 "passivate" iron, so at ordinary temperatures the metal does not dissolve in them. With strong heating, slow dissolution occurs (without release of H 2).
In razb. HNO 3 iron dissolves, goes into solution in the form of Fe 3+ cations, and the acid anion is reduced to NO *:
Fe + 4HNO 3 \u003d Fe (NO 3) 3 + NO + 2H 2 O
It dissolves very well in a mixture of HCl and HNO 3
5. Attitude to alkalis
Fe does not dissolve in aqueous solutions of alkalis. It reacts with molten alkalis only at very high temperatures.
6. Interaction with salts of less active metals
Fe + CuSO 4 \u003d FeSO 4 + Cu
Fe 0 + Cu 2+ = Fe 2+ + Cu 0
7. Interaction with gaseous carbon monoxide (t = 200°C, P)
Fe (powder) + 5CO (g) \u003d Fe 0 (CO) 5 iron pentacarbonyl
Fe(III) compounds
Fe 2 O 3 - iron oxide (III).
Red-brown powder, n. R. in H 2 O. In nature - "red iron ore".
How to get:
1) decomposition of iron hydroxide (III)
2Fe(OH) 3 = Fe 2 O 3 + 3H 2 O
2) pyrite roasting
4FeS 2 + 11O 2 \u003d 8SO 2 + 2Fe 2 O 3
3) decomposition of nitrate
Chemical properties
Fe 2 O 3 is a basic oxide with signs of amphoterism.
I. The main properties are manifested in the ability to react with acids:
Fe 2 O 3 + 6H + = 2Fe 3+ + ZH 2 O
Fe 2 O 3 + 6HCI \u003d 2FeCI 3 + 3H 2 O
Fe 2 O 3 + 6HNO 3 \u003d 2Fe (NO 3) 3 + 3H 2 O
II. Weak acid properties. Fe 2 O 3 does not dissolve in aqueous solutions of alkalis, but when fused with solid oxides, alkalis and carbonates, ferrites are formed:
Fe 2 O 3 + CaO \u003d Ca (FeO 2) 2
Fe 2 O 3 + 2NaOH \u003d 2NaFeO 2 + H 2 O
Fe 2 O 3 + MgCO 3 \u003d Mg (FeO 2) 2 + CO 2
III. Fe 2 O 3 - feedstock for iron production in metallurgy:
Fe 2 O 3 + ZS \u003d 2Fe + ZSO or Fe 2 O 3 + ZSO \u003d 2Fe + ZSO 2
Fe (OH) 3 - iron (III) hydroxide
How to get:
Obtained by the action of alkalis on soluble salts Fe 3+:
FeCl 3 + 3NaOH \u003d Fe (OH) 3 + 3NaCl
At the time of receipt of Fe(OH) 3 - red-brown mucosamorphous precipitate.
Fe (III) hydroxide is also formed during the oxidation of Fe and Fe (OH) 2 in humid air:
4Fe + 6H 2 O + 3O 2 \u003d 4Fe (OH) 3
4Fe(OH) 2 + 2Н 2 O + O 2 = 4Fe(OH) 3
Fe(III) hydroxide is the end product of hydrolysis of Fe 3+ salts.
Chemical properties
Fe(OH) 3 is a very weak base (much weaker than Fe(OH) 2). Shows noticeable acidic properties. Thus, Fe (OH) 3 has an amphoteric character:
1) reactions with acids proceed easily:
2) a fresh precipitate of Fe(OH) 3 is dissolved in hot conc. solutions of KOH or NaOH with the formation of hydroxo complexes:
Fe (OH) 3 + 3KOH \u003d K 3
In an alkaline solution, Fe (OH) 3 can be oxidized to ferrates (salts of iron acid H 2 FeO 4 not isolated in the free state):
2Fe(OH) 3 + 10KOH + 3Br 2 = 2K 2 FeO 4 + 6KBr + 8H 2 O
Fe 3+ salts
The most practically important are: Fe 2 (SO 4) 3, FeCl 3, Fe (NO 3) 3, Fe (SCN) 3, K 3 4 - yellow blood salt \u003d Fe 4 3 Prussian blue (dark blue precipitate)
b) Fe 3+ + 3SCN - \u003d Fe (SCN) 3 Fe (III) thiocyanate (blood red solution)
Iron is an element of a secondary subgroup of the eighth group of the fourth period of the periodic system of chemical elements of D. I. Mendeleev with atomic number 26. It is designated by the symbol Fe (lat. Ferrum). One of the most common metals in the earth's crust (second place after aluminum). Medium activity metal, reducing agent.
Main oxidation states - +2, +3
A simple substance iron is a malleable silver-white metal with high chemical reactivity: iron corrodes quickly at high temperatures or high humidity in the air. In pure oxygen, iron burns, and in a finely dispersed state, it ignites spontaneously in air.
Chemical properties of a simple substance - iron:
Rusting and burning in oxygen
1) In air, iron is easily oxidized in the presence of moisture (rusting):
4Fe + 3O 2 + 6H 2 O → 4Fe(OH) 3
A heated iron wire burns in oxygen, forming scale - iron oxide (II, III):
3Fe + 2O 2 → Fe 3 O 4
3Fe + 2O 2 → (Fe II Fe 2 III) O 4 (160 ° С)
2) At high temperatures (700–900°C), iron reacts with water vapor:
3Fe + 4H 2 O - t ° → Fe 3 O 4 + 4H 2
3) Iron reacts with non-metals when heated:
2Fe+3Cl 2 →2FeCl 3 (200 °С)
Fe + S – t° → FeS (600 °С)
Fe + 2S → Fe +2 (S 2 -1) (700 ° С)
4) In a series of voltages, it is to the left of hydrogen, reacts with dilute acids Hcl and H 2 SO 4, while iron (II) salts are formed and hydrogen is released:
Fe + 2HCl → FeCl 2 + H 2 (reactions are carried out without air access, otherwise Fe +2 is gradually converted by oxygen into Fe +3)
Fe + H 2 SO 4 (diff.) → FeSO 4 + H 2
In concentrated oxidizing acids, iron dissolves only when heated, it immediately passes into the Fe 3+ cation:
2Fe + 6H 2 SO 4 (conc.) – t° → Fe 2 (SO 4) 3 + 3SO 2 + 6H 2 O
Fe + 6HNO 3 (conc.) – t° → Fe(NO 3) 3 + 3NO 2 + 3H 2 O
(in the cold, concentrated nitric and sulfuric acids passivate
An iron nail immersed in a bluish solution of copper sulphate is gradually covered with a coating of red metallic copper.
5) Iron displaces metals to the right of it in solutions of their salts.
Fe + CuSO 4 → FeSO 4 + Cu
Amphotericity of iron is manifested only in concentrated alkalis during boiling:
Fe + 2NaOH (50%) + 2H 2 O \u003d Na 2 ↓ + H 2
and a precipitate of sodium tetrahydroxoferrate(II) is formed.
Technical iron- alloys of iron with carbon: cast iron contains 2.06-6.67% C, steel 0.02-2.06% C, other natural impurities (S, P, Si) and artificially introduced special additives (Mn, Ni, Cr) are often present, which gives iron alloys technically useful properties - hardness, thermal and corrosion resistance, malleability, etc. .
Blast furnace iron production process
The blast-furnace process of iron production consists of the following stages:
a) preparation (roasting) of sulfide and carbonate ores - conversion to oxide ore:
FeS 2 → Fe 2 O 3 (O 2, 800 ° С, -SO 2) FeCO 3 → Fe 2 O 3 (O 2, 500-600 ° С, -CO 2)
b) burning coke with hot blast:
C (coke) + O 2 (air) → CO 2 (600-700 ° C) CO 2 + C (coke) ⇌ 2CO (700-1000 ° C)
c) reduction of oxide ore with carbon monoxide CO in succession:
Fe2O3 →(CO)(Fe II Fe 2 III) O 4 →(CO) FeO →(CO) Fe
d) carburization of iron (up to 6.67% C) and melting of cast iron:
Fe (t ) →(C(coke)900-1200°С) Fe (g) (cast iron, t pl 1145°С)
In cast iron, cementite Fe 2 C and graphite are always present in the form of grains.
Steel production
The redistribution of cast iron into steel is carried out in special furnaces (converter, open-hearth, electric), which differ in the method of heating; process temperature 1700-2000 °C. Blowing oxygen-enriched air burns out excess carbon from cast iron, as well as sulfur, phosphorus and silicon in the form of oxides. In this case, oxides are either captured in the form of exhaust gases (CO 2, SO 2), or are bound into an easily separated slag - a mixture of Ca 3 (PO 4) 2 and CaSiO 3. To obtain special steels, alloying additives of other metals are introduced into the furnace.
Receipt pure iron in industry - electrolysis of a solution of iron salts, for example:
FeCl 2 → Fe↓ + Cl 2 (90°C) (electrolysis)
(there are other special methods, including the reduction of iron oxides with hydrogen).
Pure iron is used in the production of special alloys, in the manufacture of cores of electromagnets and transformers, cast iron is used in the production of castings and steel, steel is used as structural and tool materials, including wear-, heat- and corrosion-resistant materials.
Iron(II) oxide F EO . Amphoteric oxide with a large predominance of basic properties. Black, has an ionic structure of Fe 2+ O 2-. When heated, it first decomposes, then re-forms. It is not formed during the combustion of iron in air. Does not react with water. Decomposed by acids, fused with alkalis. Slowly oxidizes in moist air. Recovered by hydrogen, coke. Participates in the blast-furnace process of iron smelting. It is used as a component of ceramics and mineral paints. Equations of the most important reactions:
4FeO ⇌ (Fe II Fe 2 III) + Fe (560-700 ° С, 900-1000 ° С)
FeO + 2HC1 (razb.) \u003d FeC1 2 + H 2 O
FeO + 4HNO 3 (conc.) \u003d Fe (NO 3) 3 + NO 2 + 2H 2 O
FeO + 4NaOH \u003d 2H 2 O + Na 4FeO3(red.) trioxoferrate(II)(400-500 °С)
FeO + H 2 \u003d H 2 O + Fe (high purity) (350 ° C)
FeO + C (coke) \u003d Fe + CO (above 1000 ° C)
FeO + CO \u003d Fe + CO 2 (900 ° C)
4FeO + 2H 2 O (moisture) + O 2 (air) → 4FeO (OH) (t)
6FeO + O 2 \u003d 2 (Fe II Fe 2 III) O 4 (300-500 ° С)
Receipt in laboratories: thermal decomposition of iron (II) compounds without air access:
Fe (OH) 2 \u003d FeO + H 2 O (150-200 ° C)
FeSOz \u003d FeO + CO 2 (490-550 ° С)
Diiron oxide (III) - iron ( II ) ( Fe II Fe 2 III) O 4 . Double oxide. Black, has the ionic structure of Fe 2+ (Fe 3+) 2 (O 2-) 4. Thermally stable up to high temperatures. Does not react with water. Decomposed by acids. Restored by hydrogen, red-hot iron. Participates in the blast-furnace process of iron production. It is used as a component of mineral paints ( minium iron), ceramics, colored cement. The product of special oxidation of the surface of steel products ( blackening, bluing). The composition corresponds to brown rust and dark scale on iron. The use of the Fe 3 O 4 formula is not recommended. Equations of the most important reactions:
2 (Fe II Fe 2 III) O 4 \u003d 6FeO + O 2 (above 1538 ° С)
(Fe II Fe 2 III) O 4 + 8HC1 (razb.) \u003d FeC1 2 + 2FeC1 3 + 4H 2 O
(Fe II Fe 2 III) O 4 + 10HNO 3 (conc.) \u003d 3 Fe (NO 3) 3 + NO 2 + 5H 2 O
(Fe II Fe 2 III) O 4 + O 2 (air) \u003d 6Fe 2 O 3 (450-600 ° С)
(Fe II Fe 2 III) O 4 + 4H 2 \u003d 4H 2 O + 3Fe (high purity, 1000 ° C)
(Fe II Fe 2 III) O 4 + CO \u003d 3 FeO + CO 2 (500-800 ° C)
(Fe II Fe 2 III) O4 + Fe ⇌4 FeO (900-1000 ° С, 560-700 ° С)
Receipt: combustion of iron (see) in air.
magnetite.
Iron(III) oxide F e 2 O 3 . Amphoteric oxide with a predominance of basic properties. Red-brown, has an ionic structure (Fe 3+) 2 (O 2-) 3. Thermally stable up to high temperatures. It is not formed during the combustion of iron in air. Does not react with water, a brown amorphous hydrate Fe 2 O 3 nH 2 O precipitates from the solution. Slowly reacts with acids and alkalis. It is reduced by carbon monoxide, molten iron. Alloys with oxides of other metals and forms double oxides - spinels(technical products are called ferrites). It is used as a raw material in iron smelting in the blast furnace process, as a catalyst in the production of ammonia, as a component of ceramics, colored cements and mineral paints, in thermite welding of steel structures, as a sound and image carrier on magnetic tapes, as a polishing agent for steel and glass.
Equations of the most important reactions:
6Fe 2 O 3 \u003d 4 (Fe II Fe 2 III) O 4 + O 2 (1200-1300 ° С)
Fe 2 O 3 + 6HC1 (razb.) → 2FeC1 3 + ZH 2 O (t) (600 ° C, p)
Fe 2 O 3 + 2NaOH (conc.) → H 2 O+ 2 NaFeO 2 (red)dioxoferrate(III)
Fe 2 O 3 + MO \u003d (M II Fe 2 II I) O 4 (M \u003d Cu, Mn, Fe, Ni, Zn)
Fe 2 O 3 + ZN 2 \u003d ZN 2 O + 2Fe (highly pure, 1050-1100 ° С)
Fe 2 O 3 + Fe \u003d ZFeO (900 ° C)
3Fe 2 O 3 + CO \u003d 2 (Fe II Fe 2 III) O 4 + CO 2 (400-600 ° С)
Receipt in the laboratory - thermal decomposition of iron (III) salts in air:
Fe 2 (SO 4) 3 \u003d Fe 2 O 3 + 3SO 3 (500-700 ° С)
4 (Fe (NO 3) 3 9 H 2 O) \u003d 2 Fe a O 3 + 12NO 2 + 3O 2 + 36H 2 O (600-700 ° С)
In nature - iron oxide ores hematite Fe 2 O 3 and limonite Fe 2 O 3 nH 2 O
Iron(II) hydroxide F e(OH) 2 . Amphoteric hydroxide with a predominance of basic properties. White (sometimes with a greenish tinge), Fe-OH bonds are predominantly covalent. Thermally unstable. Easily oxidizes in air, especially when wet (darkens). Insoluble in water. Reacts with dilute acids, concentrated alkalis. Typical restorer. An intermediate product in the rusting of iron. It is used in the manufacture of the active mass of iron-nickel batteries.
Equations of the most important reactions:
Fe (OH) 2 \u003d FeO + H 2 O (150-200 ° C, in atm.N 2)
Fe (OH) 2 + 2HC1 (razb.) \u003d FeC1 2 + 2H 2 O
Fe (OH) 2 + 2NaOH (> 50%) \u003d Na 2 ↓ (blue-green) (boiling)
4Fe(OH) 2 (suspension) + O 2 (air) → 4FeO(OH)↓ + 2H 2 O (t)
2Fe (OH) 2 (suspension) + H 2 O 2 (razb.) \u003d 2FeO (OH) ↓ + 2H 2 O
Fe (OH) 2 + KNO 3 (conc.) \u003d FeO (OH) ↓ + NO + KOH (60 ° С)
Receipt: precipitation from solution with alkalis or ammonia hydrate in an inert atmosphere:
Fe 2+ + 2OH (razb.) = Fe(OH) 2 ↓
Fe 2+ + 2 (NH 3 H 2 O) = Fe(OH) 2 ↓+ 2NH4
Iron metahydroxide F eO(OH). Amphoteric hydroxide with a predominance of basic properties. Light brown, Fe-O and Fe-OH bonds are predominantly covalent. When heated, it decomposes without melting. Insoluble in water. It precipitates from solution in the form of a brown amorphous polyhydrate Fe 2 O 3 nH 2 O, which, when kept under a dilute alkaline solution or when dried, turns into FeO (OH). Reacts with acids, solid alkalis. Weak oxidizing and reducing agent. Sintered with Fe(OH) 2 . An intermediate product in the rusting of iron. It is used as a base for yellow mineral paints and enamels, as an exhaust gas absorber, as a catalyst in organic synthesis.
Connection composition Fe(OH) 3 is not known (not obtained).
Equations of the most important reactions:
Fe 2 O 3 . nH 2 O→( 200-250 °С, —H 2 O) FeO(OH)→( 560-700°C in air, -H2O)→Fe 2 O 3
FeO (OH) + ZNS1 (razb.) \u003d FeC1 3 + 2H 2 O
FeO(OH)→ Fe 2 O 3 . nH 2 O-colloid(NaOH (conc.))
FeO(OH)→ Na 3 [Fe(OH) 6 ]white, Na 5 and K 4, respectively; in both cases, a blue product of the same composition and structure, KFe III, precipitates. In the laboratory, this precipitate is called Prussian blue, or turnbull blue:
Fe 2+ + K + + 3- = KFe III ↓
Fe 3+ + K + + 4- = KFe III ↓
Chemical names of initial reagents and reaction product:
K 3 Fe III - potassium hexacyanoferrate (III)
K 4 Fe III - potassium hexacyanoferrate (II)
KFe III - hexacyanoferrate (II) iron (III) potassium
In addition, the thiocyanate ion NCS - is a good reagent for Fe 3+ ions, iron (III) combines with it, and a bright red (“bloody”) color appears:
Fe 3+ + 6NCS - = 3-
With this reagent (for example, in the form of KNCS salt), even traces of iron (III) can be detected in tap water if it passes through iron pipes covered with rust from the inside.
DEFINITION
Iron(II) oxide under normal conditions, it is a black powder (Fig. 1), decomposing upon moderate heating and re-forming from the decomposition products upon further heating.
After calcination, it is chemically inactive. Pyrophorene powder. Does not react with cold water. Shows amphoteric properties (with a predominance of basic). Easily oxidized by oxygen. It is reduced by hydrogen and carbon.
Rice. 1. Iron oxide (II). Appearance.
Chemical formula of iron oxide 2
The chemical formula of iron(II) oxide is FeO. The chemical formula shows the qualitative and quantitative composition of the molecule (how many and which atoms are present in it). According to the chemical formula, you can calculate the molecular weight of a substance (Ar (Fe) \u003d 56 amu, Ar (O) \u003d 16 amu):
Mr(FeO) = Ar(Fe) + Ar(O);
Mr(FeO) = 56 + 16 = 72.
Structural (graphical) formula of iron oxide 2
The structural (graphic) formula of a substance is more visual. It shows how atoms are connected to each other within a molecule. Below is the graphic formula of iron oxide (II):
Examples of problem solving
EXAMPLE 1
| Exercise | When neutralizing 25.5 g of saturated monobasic acid with an excess of sodium bicarbonate solution, 5.6 l (N.O.) of gas were released. Determine the molecular formula of the acid. |
| Solution | We write the equation for the neutralization reaction of a saturated monobasic acid with an excess of sodium bicarbonate solution in general form: C n H 2n+1 COOH + NaHCO 3 → C n H 2n+1 COONa + CO 2 + H 2 O. Calculate the amount of carbon dioxide released during the reaction: n(CO 2) \u003d V (CO 2) / V m; n(CO 2) \u003d 5.6 / 22.4 \u003d 0.25 mol. According to the reaction equation n(CO 2): n(C n H 2n+1 COOH) = 1:1, i.e. n (C n H 2n + 1 COOH) \u003d n (CO 2) \u003d 0.25 mol. Calculate the molar mass of the limiting monobasic acid: M(C n H 2n+1 COOH) = m(C n H 2n+1 COOH) / n(C n H 2n+1 COOH); M(C n H 2 n +1 COOH) \u003d 25.5 / 0.25 \u003d 102 g / mol. Let's determine the number of carbon atoms in the molecule of the limiting monobasic acid (the values of relative atomic masses taken from the Periodic Table of D.I. Mendeleev are rounded up to integers: 12 for carbon, 1 for hydrogen and 16 for oxygen): M(C n H 2n+1 COOH) = 12n + 2n + 1 + 12 + 16 + 16 +1 = 14n + 46; 14n + 46 = 102 g/mol; So the molecular formula of the limiting monobasic acid is C 4 H 9 COOH. |
| Answer | C4H9COOH |
EXAMPLE 2
| Exercise | Set the molecular formula of an alkene if it is known that 2.8 g of it can add 1120 ml (N.O.) of hydrogen chloride. |
| Solution | Let us write the equation for the reaction of the addition of hydrogen chloride to an alkene in general form: C n H 2 n + HCl → C n H 2 n +1 Cl. Calculate the amount of hydrogen chloride substance: n(HCl) = V(HCl) / V m ; n(HCl) = 1.2 / 22.4 = 0.05 mol. According to the reaction equation n(HCl): n(C n H 2n) = 1:1, i.e. n (C n H 2n) \u003d n (HCl) \u003d 0.05 mol. Calculate the molar mass of an alkene: M(C n H 2n) = m(C n H 2n) / n(C n H 2n); M(C n H 2 n) \u003d 2.8 / 0.05 \u003d 56 g / mol. Let's determine the number of carbon atoms in an alkene molecule (the values of relative atomic masses taken from the Periodic Table of D.I. Mendeleev are rounded up to integers: 12 for carbon and 1 for hydrogen): M(C n H 2 n) = 12n + 2n = 14n; 14n= 56 g/mol; So the molecular formula of the alkene is C 4 H 8. |
| Answer | C 4 H 8 |
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.
Chemical properties
Chemical properties
Fe(II) salts
Chemical properties
Chemical properties
FeO - Fe(II) oxide.
Refractory black pyrophoric powder, insoluble in water.
According to its chemical properties, FeO is a basic oxide. Reacts with acids to form salts:
FeO + 2HCl \u003d FeCl 2 + H 2 O
4FeO + O 2 = 2Fe 2 O 3
3FeO + 10HNO 3 \u003d 3Fe (NO 3) 3 + NO + 5H 2 O
Fe (OH) 2 - Fe (II) hydroxide is a white solid, insoluble in water.
According to its chemical properties, it is a weak base, it easily reacts with acids and does not react with alkalis. Fe (OH) 2 is an unstable substance: when heated without access to air, it decomposes, and spontaneously oxidizes in air:
Fe (OH) 2 \u003d FeO + H 2 O (t)
4Fe(OH) 2 + O 2 + 2H 2 O = 4Fe(OH) 3
pale green brown
The most practically important are: FeSO 4 , FeCl 2 , Fe(NO 3) 3 , FeS, FeS 2 .
The formation of complex and double salts with alkali metal and ammonium salts is characteristic:
Fe(CN) 2 + 4KCN = K 4 (yellow blood salt)
FeCl 2 + 2KCl \u003d K 2
Mora Salt
(NH 4) 2 SO 4 FeSO 4 6H 2 O
inkstone
The hydrated Fe 2+ ion has a pale green color.
1. Soluble salts of Fe 2+ in aqueous solutions undergo hydrolysis with the formation of an acidic environment:
Fe 2+ + H 2 O ↔ FeOH + + H +
2. Show common properties of typical salts (ion-exchange interactions):
FeS + 2HCl \u003d FeCl 2 + H 2 S
FeCl 2 + 2NaOH = Fe(OH) 2 ↓ + 2NaCl
FeSO 4 + BaCl 2 \u003d FeCl 2 + BaSO 4 ↓
3. Easily oxidized by strong oxidizing agents
Fe 2+ - 1ē → Fe 3+
10Fe +2 SO 4 + 2KMnO 4 + 8H 2 SO 4 = 5Fe +3 (SO 4) 3 + K 2 SO 4 + 2MnSO 4 + 8H 2 O
4. Qualitative reactions for the detection of Fe 2+ cations:
a) 3Fe 2+ + 2 3- = Fe 3 2 ↓
red blood salt turnbull blue
(dark blue precipitate)
b) under the action of alkali, a pale green precipitate of Fe (OH) 2 precipitates, which gradually turns green in air, and then turns into brown Fe (OH) 3.
Fe(III) compounds
Fe 2 O 3 - iron oxide (III)
Red-brown powder, insoluble in water. In nature - "red iron ore".
Fe 2 O 3 is a basic oxide with signs of amphoterism.
1. The main properties are manifested in the ability to react with acids:
Fe 2 O 3 + 6HCl \u003d 2FeCl 3 + 3H 2 O
Fe 2 O 3 + 6HNO 3 \u003d 2Fe (NO 3) 3 + 3H 2 O
2. Fe 2 O 3 does not dissolve in aqueous solutions of alkalis, but when fused with solid oxides, alkalis and carbonates, ferrites are formed:
Fe 2 O 3 + CaO \u003d Ca (FeO 2) 2 (t)
Fe 2 O 3 + 2NaOH \u003d 2NaFeO 2 + H 2 O (t)
Fe 2 O 3 + MgCO 3 \u003d Mg (FeO 2) 2 + CO 2 (t)
3. Fe 2 O 3 - feedstock for iron production in metallurgy:
Fe 2 O 3 + 3C = 2Fe + 3CO or Fe 2 O 3 + 3CO = 2Fe + 3CO 2
Fe (OH) 3 - iron (III) hydroxide
Fe(OH) 3 is a very weak base (much weaker than Fe(OH) 2). Fe (OH) 3 has an amphoteric character:
1) Reactions with acids proceed easily:
Fe(OH) 3 + 3HCl = FeCl 3 + 3H 2 O
2) A fresh precipitate of Fe (OH) 3 dissolves in hot concentrated solutions of KOH or NaOH with the formation of hydroxo complexes:
Fe (OH) 3 + 2KOH \u003d K 3
In an alkaline solution, Fe (OH) 3 can be oxidized to ferrates (salts of iron acid H 2 FeO 4 not isolated in the free state):
2Fe(OH) 3 + 10KOH + 3Br 2 = 2K 2 FeO 4 + 6KBr + 8H 2 O
Fe 3+ salts
The most practically important are:
Fe 2 (SO 4) 3 , FeCl 3 , Fe(NO 3) 3 , Fe(SCN) 3 , K 3
The formation of double salts - iron alum is characteristic:
(NH 4) Fe (SO 4) 2 12H 2 O
KFe(SO 4) 2 12H 2 O
Fe 3+ salts are often colored both in the solid state and in aqueous solution. This is due to the presence of hydrated forms or hydrolysis products.
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