Aluminum oxide, properties, preparation, chemical reactions

Interaction of aluminum with simple substances

with oxygen

When absolutely pure aluminum comes into contact with air, aluminum atoms located in the surface layer instantly interact with oxygen in the air and form a thin, tens of atomic layers thick, durable oxide film of Al2O3 composition, which protects aluminum from further oxidation. It is also impossible to oxidize large samples of aluminum even at very high temperatures. However, fine aluminum powder burns quite easily in a burner flame:

with halogens

Aluminum reacts very vigorously with all halogens. Thus, the reaction between mixed aluminum and iodine powders occurs already at room temperature after adding a drop of water as a catalyst. Equation for the interaction of iodine with aluminum:

Aluminum also reacts with bromine, which is a dark brown liquid, without heating. Simply add a sample of aluminum to liquid bromine: a violent reaction immediately begins, releasing a large amount of heat and light:

The reaction between aluminum and chlorine occurs when heated aluminum foil or fine aluminum powder is added to a flask filled with chlorine. Aluminum burns effectively in chlorine according to the equation:

with sulfur

When heated to 150-200 o C or after igniting a mixture of powdered aluminum and sulfur, an intense exothermic reaction begins between them with the release of light:

- aluminum sulfide

with nitrogen

When aluminum reacts with nitrogen at a temperature of about 800 o C, aluminum nitride is formed:

with carbon

At a temperature of about 2000 o C, aluminum reacts with carbon and forms aluminum carbide (methanide), containing carbon in the -4 oxidation state, as in methane.

Interaction of aluminum with complex substances

with water

As mentioned above, a stable and durable oxide film of Al2O3 prevents aluminum from oxidizing in air. The same protective oxide film makes aluminum inert towards water. When removing the protective oxide film from the surface by methods such as treatment with aqueous solutions of alkali, ammonium chloride or mercury salts (amalgiation), aluminum begins to react vigorously with water to form aluminum hydroxide and hydrogen gas:

with metal oxides

After igniting a mixture of aluminum with oxides of less active metals (to the right of aluminum in the activity series), an extremely violent, highly exothermic reaction begins. Thus, in the case of interaction of aluminum with iron (III) oxide, a temperature of 2500-3000 o C develops. As a result of this reaction, high-purity molten iron is formed:

This method of obtaining metals from their oxides by reduction with aluminum is called aluminothermy or aluminothermy.

with non-oxidizing acids

The interaction of aluminum with non-oxidizing acids, i.e. with almost all acids, except concentrated sulfuric and nitric acids, leads to the formation of an aluminum salt of the corresponding acid and hydrogen gas:

2Al 0 + 6H + = 2Al 3+ + 3H2 0 ;

with oxidizing acids

-concentrated sulfuric acid

The interaction of aluminum with concentrated sulfuric acid under normal conditions and at low temperatures does not occur due to an effect called passivation. When heated, the reaction is possible and leads to the formation of aluminum sulfate, water and hydrogen sulfide, which is formed as a result of the reduction of sulfur, which is part of sulfuric acid:

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Such a deep reduction of sulfur from the oxidation state +6 (in H2SO4) to the oxidation state -2 (in H2S) occurs due to the very high reducing ability of aluminum.

- concentrated nitric acid

Under normal conditions, concentrated nitric acid also passivates aluminum, which makes it possible to store it in aluminum containers. Just as in the case of concentrated sulfuric acid, the interaction of aluminum with concentrated nitric acid becomes possible with strong heating, and the reaction predominantly occurs:

- dilute nitric acid

The interaction of aluminum with diluted nitric acid compared to concentrated nitric acid leads to products of deeper nitrogen reduction. Instead of NO, depending on the degree of dilution, N2O and NH4NO3 can be formed:

with alkalis

Aluminum reacts both with aqueous solutions of alkalis:

and with pure alkalis during fusion:

In both cases, the reaction begins with the dissolution of the protective film of aluminum oxide:

In the case of an aqueous solution, aluminum, cleared of the protective oxide film, begins to react with water according to the equation:

The resulting aluminum hydroxide, being amphoteric, reacts with an aqueous solution of sodium hydroxide to form soluble sodium tetrahydroxoaluminate:

Aluminum is a reactive metal, but a strong oxide film determines its resistance under normal conditions. In almost all chemical reactions, aluminum exhibits reducing properties.

Interaction with non-metals

It interacts with oxygen only in a finely divided state at high temperatures:

the reaction is accompanied by a large release of heat.

Above 200°C it reacts with sulfur to form aluminum sulfide:

At 500°C – with phosphorus, forming aluminum phosphide:

At 800°C it reacts with nitrogen, and at 2000°C – with carbon, forming nitride and carbide:

It reacts with chlorine and bromine under normal conditions, and with iodine when heated, in the presence of water as a catalyst:

Does not interact directly with hydrogen.

With metals it forms alloys that contain intermetallic compounds - aluminides, for example, CuAl2, CrAl7, FeAl3, etc.

Interaction with water

Aluminum purified from the oxide film vigorously interacts with water:

As a result of the reaction, slightly soluble aluminum hydroxide is formed and hydrogen is released.

Interaction with acids

Easily reacts with dilute acids, forming salts:

8Al + 30HNO3 = 8Al(NO3)3 + 3N2O + 15H2O (nitrogen and ammonium nitrate can also be the product of nitric acid reduction).

It does not react with concentrated nitric and sulfuric acids at room temperature; when heated, it reacts to form a salt and the acid reduction product:

Interaction with alkalis

Aluminum is an amphoteric metal; it reacts easily with alkalis:

in solution to form sodium tetrahydroxodiaquaaluminate:

when fused to form aluminates:

Recovery of metals from oxides and salts

Aluminum is an active metal, capable of displacing metals from their oxides. This property of aluminum has found practical application in metallurgy:

Metals are one of the most convenient materials to process. They also have their own leaders. For example, the basic properties of aluminum have been known to people for a long time. They are so suitable for everyday use that this metal has become very popular. What are the properties of aluminum as a simple substance and as an atom, we will consider in this article.

Nitric acid (HNO3)

It is a very strong acid with a pungent odor.

• Dissolves all metals except aluminum and iron.
• Low price. From 15 rub. per kilogram for technical and from 50 rubles. for pure acid.
• Prevalence - you can buy nitric acid in any city, in many online stores, in all volumes and concentrations.
• Multifunctionality. This compound is also used as a rocket fuel reagent, fertilizer and raw material for medicines (nitroglycerin).

• Volatility of nitric acid. The concentrated compound “smoke”, and in bright light it decomposes into nitric oxide and water. It should be stored in dark containers.
• Suffocating smell.
• Virulence. Acid is dangerous for the human body, causing suffocation and intoxication if exposed to unprotected contact. You need to work with it wearing a mask and gloves.
• Slow action. If the compound is not mixed with other acids, then 2 mm of metal will dissolve in 5 hours.
• Dissolving not only the desired object, but also the surrounding objects - concrete, wood, etc.

History of the discovery of aluminum

For a long time, man has known the compound of the metal in question - potassium alum. It was used as a means that could swell and bind together the components of the mixture; this was also necessary in the manufacture of leather products. The existence of aluminum oxide in its pure form became known in the 18th century, in its second half. However, no pure substance was obtained.

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The scientist H. K. Ørsted was the first to isolate the metal from its chloride. It was he who treated the salt with potassium amalgam and isolated gray powder from the mixture, which was aluminum in its pure form.

Then it became clear that the chemical properties of aluminum are manifested in its high activity and strong reducing ability. Therefore, no one else worked with him for a long time.

However, in 1854, the Frenchman Deville was able to obtain metal ingots by electrolysis of the melt. This method is still relevant today. Especially mass production of valuable material began in the 20th century, when the problems of generating large amounts of electricity in enterprises were solved.

Today, this metal is one of the most popular and used in construction and the household industry.

General characteristics of the aluminum atom

If we characterize the element in question by its position in the periodic table, then several points can be distinguished.

1. Serial number – 13.
2. Located in the third small period, third group, main subgroup.
3. Atomic mass – 26.98.
4. The number of valence electrons is 3.
5. The configuration of the outer layer is expressed by the formula 3s 2 3p 1.
6. The name of the element is aluminum.
7. Metallic properties are strongly expressed.
8. It has no isotopes in nature; it exists only in one form, with a mass number of 27.
9. The chemical symbol is AL, read as “aluminum” in formulas.
10. The oxidation state is one, equal to +3.

The chemical properties of aluminum are fully confirmed by the electronic structure of its atom, because having a large atomic radius and low electron affinity, it is capable of acting as a strong reducing agent, like all active metals.

What have we learned?

Aluminum is an amphoteric active metal with constant valence. It has low density, high electrical conductivity, and plasticity. Attracted by a magnet only in the presence of a magnetic field. Aluminum reacts with oxygen, forming a protective film that prevents reactions with water, concentrated nitric and sulfuric acids. When heated, it reacts with non-metals and concentrated acids, and under normal conditions - with halogens and dilute acids. In oxides it displaces less active metals. Does not react with hydrogen.

Aluminum is a ductile and lightweight white metal coated with a silver matte oxide film. In the periodic system of D.I. Mendeleev, this chemical element is designated as Al (Aluminium) and is located in the main subgroup of group III, third period, under atomic number 13. You can buy aluminum on our website.

Aluminum as a simple substance: physical properties

If we talk about aluminum as a simple substance, then it is a silvery-white shiny metal. In air it quickly oxidizes and becomes covered with a dense oxide film. The same thing happens when exposed to concentrated acids.

The presence of such a feature makes products made of this metal resistant to corrosion, which, naturally, is very convenient for people. That is why aluminum is so widely used in construction. The properties of the substance are also interesting in that this metal is very light, yet durable and soft. The combination of such characteristics is not available to every substance.

There are several basic physical properties that are characteristic of aluminum.

1. High degree of malleability and ductility. Light, strong and very thin foil is made from this metal, and it is also rolled into wire.
2. Melting point – 660 0 C.
3. Boiling point – 2450 0 C.
4. Density – 2.7 g/cm3.
5. The crystal lattice is volumetric face-centered, metal.
6. Type of connection – metal.

The physical and chemical properties of aluminum determine the areas of its application and use. If we talk about everyday aspects, then the characteristics we have already discussed above play a big role. As a lightweight, durable and anti-corrosion metal, aluminum is used in aircraft and shipbuilding. Therefore, these properties are very important to know.

Chemical properties of aluminum

From a chemical point of view, the metal in question is a strong reducing agent that is capable of exhibiting high chemical activity while being a pure substance. The main thing is to remove the oxide film. In this case, activity increases sharply.

The chemical properties of aluminum as a simple substance are determined by its ability to react with:

It does not interact with water under normal conditions. In this case, of the halogens, without heating, it reacts only with iodine. Other reactions require temperature.

Examples can be given to illustrate the chemical properties of aluminum. Equations of reactions of interaction with:

• acids – AL + HCL = AlCL3 + H2;
• alkalis – 2Al + 6H2O + 2NaOH = Na[Al(OH)4] + 3H2;
• halogens – AL + Hal = ALHal3;
• gray – 2AL + 3S = AL2S3.

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In general, the most important property of the substance in question is its high ability to restore other elements from their compounds.

What acids corrode metal?

Sulfuric, perchloric and phosphoric acids in high concentrations are also suitable.

• corrode iron;
• act quickly, but you need to remember that “fast” in chemistry is a very broad concept;
• availability - these acids are easier to find than nitric acid;
• light does not affect connections in any way;
• resistance to low temperatures - if, for example, sulfuric acid freezes, its properties will not change.

• Intolerance to high temperatures. Acids can “extinguish” - they themselves will not be damaged after this, but the storage location will be difficult to restore.
• Difficulty of work. It is necessary to follow safety rules; it is better not to touch flasks with compounds with bare hands. You will need to buy special equipment if you are going to do anything with acids.

Distribution in nature

In terms of prevalence among other metal elements, aluminum ranks first. It is contained in the earth's crust 8.8%. If we compare it with non-metals, then its place will be third, after oxygen and silicon.

Due to its high chemical activity, it is not found in pure form, but only as part of various compounds. For example, there are many known ores, minerals, and rocks that contain aluminum. However, it is extracted only from bauxite, the content of which in nature is not very high.

The most common substances containing the metal in question:

• feldspars;
• bauxite;
• granites;
• silica;
• aluminosilicates;
• basalts and others.

In small quantities, aluminum is necessarily found in the cells of living organisms. Some species of club mosses and marine inhabitants are capable of accumulating this element inside their bodies throughout their lives.

Receipt

The physical and chemical properties of aluminum make it possible to obtain it only in one way: by electrolysis of a melt of the corresponding oxide. However, this process is technologically complex. The melting point of AL2O3 exceeds 2000 0 C. Because of this, it cannot be subjected to electrolysis directly. Therefore, proceed as follows.

1. Bauxite is mined.
2. They are cleaned of impurities, leaving only aluminum oxide.
3. Then the cryolite is melted.
4. Oxide is added there.
5. This mixture is electrolyzed and pure aluminum and carbon dioxide are obtained.

The product yield is 99.7%. However, it is possible to obtain even purer metal, which is used for technical purposes.

Application

The mechanical properties of aluminum are not so good that it can be used in its pure form. Therefore, alloys based on this substance are most often used. There are many of these, you can name the most basic ones.

1. Duralumin.
2. Aluminum-manganese.
3. Aluminum-magnesium.
4. Aluminum-copper.
5. Silumins.
6. Avial.

Their main difference is, naturally, third-party additives. All of them are based on aluminum. Other metals make the material more durable, corrosion-resistant, wear-resistant and easy to process.

There are several main areas of application of aluminum, both in pure form and in the form of its compounds (alloys).

1. For the production of wire and foil used in everyday life.
2. Making dishes.
3. Aircraft manufacturing.
4. Shipbuilding.
5. Construction and architecture.
6. Space industry.
7. Creation of reactors.

Together with iron and its alloys, aluminum is the most important metal. It was these two representatives of the periodic table that found the most extensive industrial application in human hands.

Literature

1. “Ventilated facades: pros and cons.” // “Construction Technologies”, No. 1 (42), 2006, p. 6–18.

2. Weeks K. E., Block F. E. “Thermodynamic properties of 65 elements, their oxides, halides, carbides and nitrides.” - M.: “Metallurgy”, 1965.

3. Zeng D., Pankov E. The best recycling technology and equipment for today's Russian market with case study at VMC, Russia.//Proceedings of the 3rd international conference “Aluminium Recycling”. Moscow, March 29–31, 2006

4. Dobatkin V.I., Gabidullin R.M., Kolachev B.A., Makarov G.S. “Gases and oxides in aluminum wrought alloys.” - M.: “Metallurgy”, 1976.

5. “Oxidation of metals” (edited by J. Benard). T. 1. - M.: "Metallurgy", 1968.

6. Fire Resistance and Flame Spread Performance of Aluminum and Aluminum Alloys. Second Edition. The Aluminum Association, Inc. July 2002. P. 21.

7. “Aluminum alloys (properties, processing, application).” - M.: “Metallurgy”, 1979.

8. Miklyaev P. G. “Mechanical properties of light alloys at temperatures and pressure processing rates.” Directory. - M.: “Metallurgy”, 1994.

9. “Aluminum fire-resistant systems Schüco.” // “Windows, doors, facades.” Issue 17. 2006, p. 134–137.

Properties of aluminum hydroxide

Hydroxide is the most common compound that aluminum forms. Its chemical properties are the same as those of the metal itself - it is amphoteric. This means that it is capable of exhibiting a dual nature, reacting with both acids and alkalis.

Aluminum hydroxide itself is a white gelatinous precipitate. It is easily obtained by reacting aluminum salts with alkali or ammonium hydroxide. When reacting with acids, this hydroxide gives the usual corresponding salt and water. If the reaction occurs with an alkali, then hydroxo complexes of aluminum are formed, in which its coordination number is 4. Example: Na[Al(OH)4] – sodium tetrahydroxoaluminate.

What acid quickly corrodes metal?

It is better to use compounds of several substances, for example, “royal vodka”. It is a mixture of one part nitric acid and three parts hydrochloric acid. The oxidizing properties of such a compound are very strong - even gold can be dissolved.

“Royal vodka” cannot be stored openly, because the chlorine will evaporate from it and the compound will lose its basic properties. But in a few minutes the metal will not dissolve even this substance - you will have to wait a couple of hours to achieve the desired effect.

If you want to increase the reaction speed, you can apply acid to the thread (apply without interruption) and move this thread like a metal saw.

Acids are not the best solution to the problem. It is much more effective to use gases, an angle grinder, thermite or an autogen (gas cutter).

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