The most important compounds of aluminum. Aluminum Chemistry Antibacterial properties of aluminum hydroxide
One of the most widely used substances in the industry is aluminum hydroxide. This article about him will be speech.
What is hydroxide?
This is a chemical compound that is formed when the interaction of oxide with water. There are three types of their varieties: acid, basic and amphoteric. The first and second are divided into groups depending on their chemical activity, properties and formulas.
What is amphoteric substances?
Amphoteric can be oxides and hydroxides. These are such substances for which the acidic and basic properties are characterized, depending on the reaction conditions used by the reagents, etc. The amphoteric oxides include two types of iron oxide, manganese oxide, lead, beryllium, zinc, and aluminum . The latter, by the way, is most often obtained from its hydroxide. The amphoteric hydroxides include hydroxide beryllium, iron, as well as aluminum hydroxide, which we today and consider in our article.
Physical properties of aluminum hydroxide
This chemical compound is a solid white substance. It does not dissolve in water.
Aluminum hydroxide - Chemical properties
As mentioned above, this is the most vivid representative of the group of amphoteric hydroxides. Depending on the reaction conditions, it may exhibit both the main and acidic properties. This substance is capable of dissolving in acids, while the salt and water is formed.
For example, if mixed with a chlorine acid is equal, then we obtain aluminum chloride with water also in the same proportions. Also, another substance with which aluminum hydroxide reacts is sodium hydroxide. This is a typical main hydroxide. If you mix in equal amounts, the substance under consideration and sodium hydroxide solution, we will get a compound called sodium tetrahydrokoxalulum. Its chemical structure contains a sodium atom, an aluminum atom, four oxygen atoms and hydrogen. However, when fusing these substances, the reaction is somewhat differently, and it is not formed this connection. As a result of this process, it is possible to obtain a sodium metalulum (in its formula, it is part of one atom of sodium and aluminum and two oxygen atoms) with water in equal proportions, provided that it is mixed by the same amount of dry sodium hydroxides and aluminum and to act on them with high temperatures. If it is mixed with sodium hydroxide in other proportions, it is possible to obtain a hexagidroxaluluminate sodium, which contains three sodium atoms, one aluminum atom and six oxygen and hydrogen. In order to formed this substance, it is necessary to mix the substance under consideration and sodium hydroxide solution in proportions 1: 3, respectively. According to the principle described above, it is possible to obtain compounds called tetrahydroxyaluminate potassium and hexagidroxyaluminate potassium. Also, the substance under consideration is subject to decomposition when exposed to very high temperatures. Due to this kind of chemical reaction, aluminum oxide is formed, which also has amphoteriness, and water. If you take 200 g of hydroxide and heat it, then we obtain 50 g of oxide and 150 g of water. In addition to peculiar chemical properties, this substance also exhibits the usual properties for all hydroxides. It enters into interaction with metals salts that have lower chemical activity than aluminum. For example, you can consider the reaction between it and copper chloride for which you need to take them in a 2: 3 ratio. At the same time, water-soluble aluminum chloride and precipitate in the form of hydroxide of the downturn in the proportions 2: 3. Also, the substance in question reacts with oxides of such metals, for example, you can take the connection of the same copper. For the reaction, aluminum hydroxide and oxide can be required in a 2: 3 ratio, resulting in obtaining aluminum oxide and copper hydroxide. The properties that were described above also possess other amphoteric hydroxides, such as iron or beryllium hydroxide.
What is sodium hydroxide?
As seen above, there are many variants of chemical reactions of aluminum hydroxide with sodium hydroxide. What is this substance? This is a typical main hydroxide, that is, a chemically active basis, soluble in water base. It has all the chemical properties that are characteristic of the main hydroxides.
That is, it can be dissolved in acids, for example, when mixing sodium hydroxide with chlorine acid in equal amounts, it is possible to obtain a food salt (sodium chloride) and water in proportion of 1: 1. Also, this hydroxide reacts with metals salts, which have lower chemical activity than sodium, and their oxides. In the first case, the standard exchange reaction occurs. When adding to it, for example, silver chloride, sodium chloride and silver hydroxide is formed, which falls into a precipitate (the exchange reaction is feasible only if one of the substances obtained in its result will be a precipitate, gas or water). When the hydroxide is added to sodium, for example, zinc oxide, we obtain the latter and water hydroxide. However, much more specific is the reactions of this aloh hydroxide, which were described above.
Getting Aloh.
When we have already considered the main chemical properties, you can talk about how it is mined. The main method of obtaining this substance is to carry out a chemical reaction between the salt of aluminum and sodium hydroxide (potassium hydroxide can also be used).
With this kind of reaction, Aloh itself is formed, falling into a white precipitate, as well as a new salt. For example, if you take aluminum chloride and add three times more potassium hydroxide to it, then the chemical compounds are considered in the article and three times more potassium chloride. There is also a method for producing Aloh, which provides a chemical reaction between the solution of aluminum salt and the carbonate of the base metal, for the example, take sodium. To obtain aluminum hydroxide, kitchen salt and carbon dioxide in proportions 2: 6: 3, it is necessary to mix aluminum chloride, sodium carbonate (soda) and water in a 2: 3 ratio.
Where is the aluminum hydroxide?
Aluminum hydroxide finds its use in medicine.
Due to its ability to neutralize acids, preparations with its content are recommended when heartburn. It is also discharged in ulcers, acute and chronic inflammatory intestinal processes. In addition, aluminum hydroxide is used in the manufacture of elastomers. It is also widely used in the chemical industry for the synthesis of aluminum oxide, sodium aluminates - these processes were considered above. In addition, it is often used during water purification from pollution. Also, this substance is widely used in the manufacture of cosmetics.
Where are the substances that can be obtained with it?
Aluminum oxide, which can be obtained due to thermal decomposition of hydroxide, is used in the manufacture of ceramics, is used as a catalyst for various chemical reactions. Sodium tetrahydroxalummate finds its use in tissue coloring technology.
Aluminum hydroxide, characteristics, properties and reception, chemical reactions.
Aluminum hydroxide is an inorganic substance, has a chemical formula AL (OH) 3.
Brief characteristic of aluminum hydroxide:
Aluminum hydroxide - inorganic matter white.
Chemical formula of aluminum hydroxide Al (OH) 3.
Poor dissolved in water.
It has the ability to adsorb various substances.
Aluminum hydroxide modifications:
Four crystalline modifications of aluminum hydroxide are known: Gibbsit, Bayerit, Doyleit and Nordstranitis.
Gibbsite is indicated by the γ-form of aluminum hydroxide, and the bayerite - α-form of aluminum hydroxide.
Gibbsit is the most chemically stable form of aluminum hydroxide.
Physical properties of aluminum hydroxide:
| Parameter name: | Value: |
| Chemical formula | Al (OH) 3 |
| Synonyms and foreign language names for aluminum hydroxide α-form | potassium Hydroxide (English) aLUMINUM HYDROXIDE α-FORM (eng.) bayerit (rus.) |
| Synonyms and foreign language names for aluminum hydroxide γ-form | potassium Hydroxide (English) aLUMINIUM HYDROXIDE (English) aLUMINUM HYDROXIDE (English) hydrargillite (English) gibbsit (Rus.) hydrargillite (Rus.) |
| Type of substance | inorganic |
| Appearance of aluminum hydroxide α-form | colorless monoclinic crystals |
| Appearance of aluminum hydroxide γ-form | white monoclinic crystals |
| Color | white, colorless |
| Taste | —* |
| Smell | — |
| Aggregate state (at 20 ° C and atmospheric pressure 1 atm.) | solid |
| The density of aluminum hydroxide γ-form (state of the substance is a solid, at 20 ° C), kg / m 3 | 2420 |
| Density of aluminum hydroxide γ-form (state of substance - solid, at 20 ° C), g / cm 3 | 2,42 |
| The decomposition temperature of the aluminum hydroxide α-form, ° C | 150 |
| The decomposition temperature of aluminum hydroxide γ-form, ° C | 180 |
| Molar mass, g / mol | 78,004 |
* Note:
- there is no data.
Obtaining aluminum hydroxide:
Aluminum hydroxide is obtained as a result of the following chemical reactions:
- 1. as a result of the interaction of aluminum chloride and sodium hydroxide :
ALCL 3 + 3NAOH → AL (OH) 3 + 3NACL.
Aluminum hydroxide is also obtained by the interaction of aluminum salts with aqueous sinomy solutions, avoiding their excess.
- 2. as a result of the interaction of aluminum chloride, sodium and water carbonate:
2AlCl 3 + 3NA 2 CO 3 + 3H 2 O → 2AL (OH) 3 + 3CO 2 + 6NACL.
At the same time, aluminum hydroxide falls in the form of a white chenish sediment.
Aluminum hydroxide is also obtained by the interaction of water-soluble salts aluminum with alkali metal carbonates.
Chemical properties of aluminum hydroxide. Chemical reactions of aluminum hydroxide:
Aluminum hydroxide has amphoteric properties, i.e., possesses both the main and acidic properties.
The chemical properties of aluminum hydroxide are similar to the properties of hydroxides of other amphoteric metals. Therefore, the following chemical reactions are characteristic of it:
1. Aluminum hydroxide reaction with sodium hydroxide:
Al (OH) 3 + NaOH → Naalo 2 + 2H 2 O (T \u003d 1000 ° C),
Al (OH) 3 + 3NAOH → Na 3,
Al (OH) 3 + NaOH → Na.
As a result, the reaction is formed in the first case - the aluminate of sodium and water, in the second - hexagidroxaluluminate of sodium, in the third - tetrahydroxyaluminate sodium. In the third case as sodium hydroxide
2. aluminum hydroxide reaction with potassium hydroxide:
Al (OH) 3 + KOH → Kalo 2 + 2H 2 O (T \u003d 1000 ° C),
AL (OH) 3 + KOH → K.
As a result, the reaction is formed in the first case - the aluminate of potassium and water, in the second - tetrahydroxyalumumut of potassium. In the second case as potassium hydroxide Concentrated solution is used.
3. aluminum hydroxide reaction with nitric acid:
Al (OH) 3 + 3HNO 3 → AL (NO 3) 3 + 3H 2 O.
As a result of the reaction, aluminum nitrates are formed and water.
Similarly, the reactions of aluminum hydroxide and with other acids are underway.
4. aluminum hydroxide reaction with fluoride hydrogen:
Al (OH) 3 + 3HF → ALF 3 + 3H 2 O,
6HF + Al (OH) 3 → H 3 + 3H 2 O.
As a result, the reaction is formed in the first case - aluminum and water fluoride, in the second - hydrogen hexafluoroaluminum and water. In this case, the fluorine hydrogen in the first case, as a starting material is used as a solution.
5. aluminum hydroxide reaction with bromomic:
Al (OH) 3 + 3HBR → ALBR 3 + 3H 2 O.
As a result of the reaction, aluminum and water bromide are formed.
6. aluminum hydroxide reaction with iodine hydrogen:
Al (OH) 3 + 3HI → ALI 3 + 3H 2 O.
As a result of the reaction, aluminum and water iodide are formed.
7. the thermal decomposition reaction of aluminum hydroxide:
Al (OH) 3 → ALO (OH) + H 2 O (T \u003d 200 ° C),
2AL (OH) 3 → AL 2 O 3 + 3H 2 O (T \u003d 575 ° C).
As a result, the reaction is formed in the first case - aluminum and water metagidroxide, in the second - aluminum and water oxide.
8. aluminum hydroxide reaction and sodium carbonate:
2AL (OH) 3 + Na 2 CO 3 → 2NAALO 2 + CO 2 + 3H 2 O.
As a result of the reaction, sodium aluminate, carbon monoxide (IV) and water are formed.
10. aluminum and calcium hydroxide hydroxide reaction:
Ca (OH) 2 + 2AL (OH) 3 → CA 2.
As a result of the reaction, the calcium tetrahydroxyalumum is formed.
Application and use of aluminum hydroxide:
Aluminum hydroxide is used in water purification (as an adsorbing substance), in medicine, as a filler in a toothpaste (as an abrasive substance), plastics and plastics (as antipiren).
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2S 2P 3S 3P
Electronic configuration aluminumin excited state :
+ 13Al * 1S 2
2S 2 2P 6 3S 1 3P 2 1S 2S 2P 3S 3P 
Aluminum Shows paramagnetic properties. Aluminum in the air quickly forms durable oxide filmsprotecting the surface from further interaction therefore resistant to corrosion.
Physical properties
Aluminum - Light metal silver-white color, easy to form molding, casting, machining. It has high heat and electrical conductivity.
Melting point 660 ° C, Boiling point 1450 ° C, Aluminum density 2.7 g / cm 3.
Finding in nature
Aluminum - the most common metal in nature, and the 3rd prevalence among all elements (after oxygen and silicon). The content in the earth's crust is about 8%.
In nature, aluminum is found in the form of connections:
Al 2 O 3 · H 2 O Boxites(with impurities SiO. 2, Fe 2 O 3, Caco 3)- Aluminum oxide hydrate
Corundum Al 2 O 3.Red Corundum is called ruby, blue corundum is called sapphire.
Methods for getting
Aluminum Forms solid chemical bond with oxygen. Therefore, traditional methods for producing aluminum reduction from oxide proceeds require high energy costs. For industrial aluminum production is used by the Hall-Era process. To reduce the melting point of aluminum oxide dissolved in molten cryolite (at a temperature of 960-970 ° C) Na 3 ALF 6, and then subjected electrolysis with carbon electrodes. When dissolved in the cryolite melt, aluminum oxide disintegrates on the ions:
Al 2 O 3 → AL 3+ + ALO 3 3-
On the cathode occurs restoration of aluminum ions:
To: Al 3+ + 3e → Al 0
On the anode Oxidation occurs aluminate ions:
A: 4ALO 3 3- - 12E → 2AL 2 O 3 + 3O 2
The total aluminum oxide melt electrolysis equation:
2AL 2 O 3 → 4Al + 3O 2
Laboratory methodaluminum production is to reduce aluminum from anhydrous aluminum chloride with metal potassium:
ALCL 3 + 3K → 4AL + 3KCL
Qualitative reactions
High-quality reaction to aluminum ions - interaction excessalum aluminum salts . This forms white amorphous sediment aluminum hydroxide.
for example , aluminum chloride S. interacts sodium hydroxide:
In the further addition of alkali, amphoteric aluminum hydroxide dissolves with formation tetrahydroxalulumita:
Al (OH) 3 + NaOH \u003d Na
note if we put salt aluminum in excess solution of alkali, then the white precipitate of aluminum hydroxide is not formed, because In excess alkali, the aluminum connection immediately go into complex:
ALCL 3 + 4NAOH \u003d NA
Aluminum salts can be detected using an ammonia aqueous solution. In the interaction of soluble salts of aluminum with an aqueous solution of ammonia also in there is a translucent studio of aluminum hydroxide precipitate.
ALCL 3 + 3NH 3 · H 2 O \u003d Al (OH) 3 ↓ + 3 NH 4 Cl
Al 3+ + 3NH 3 · H 2 O \u003d Al (OH) 3 ↓ + 3 NH 4 +
Videopy The interaction of the aluminum chloride solution with a solution of ammonia can be viewed
Chemical properties
1. Aluminum - strong reducing agent . So he reacts with many nemmetallas .
1.1. Aluminum react S. halogenswith education halogenide:
1.2. Aluminum reacts with gray with education sulfides.:
2Al + 3s → Al 2 S 3
1.3. Aluminum reactfrom phosphorus . At the same time, binary compounds are formed - phosphida:
Al + P → ALP
Aluminum does not react with hydrogen .
1.4. With nitrogen aluminumreacts when heated to 1000 o C with formation nitrida:
2AL + N 2 → 2Aln
1.5. Aluminum reacts with carbon with education aluminum carbide:
4Al + 3C → Al 4 C 3
1.6. Aluminum interacts S. oxygen with education oxide:
4Al + 3O 2 → 2Al 2 O 3
Videopy Aluminum interaction with isoor of air (Aluminum burning in air) can be viewed.
2. Aluminum interacts by S. complex substances:
2.1. Reacts Lie aluminum from water? The answer to this question you can easily find if you dig a little in your memory. Surely at least once in my life you met with aluminum saucepans or aluminum cutlery. I loved such a question to ask students on the exams. What is the most amazing answer, I received different answers - someone aluminum reacted with water. And very, very many surrendered after the question: "Maybe aluminum reacts with water when heated?" When heated aluminum reacted with water already at half of the respondents))
Nevertheless, it is easy to understand that aluminum is still with water under normal conditions (and when heated) do not interact. And we have already mentioned why: due to education oxide film . But if the aluminum is cleaned from oxide film (for example, amalgamate), then he will interact with water very active with education aluminum hydroxide and hydrogen:
2AL 0 + 6H 2 + O → 2AL +3 ( OH) 3 + 3H 2 0
Aluminum amalgam can be obtained, withstanding aluminum pieces in mercury chloride solution (II):
Videopy The interactions of the amalgam aluminum with water can be viewed.
2.2. Aluminum interact S. mineral acids (with salt, phosphoric and dilute sulfuric acid) with explosion. At the same time, salt and hydrogen are formed.
for example, aluminum reacts violently with hydrochloric acid :
2.3. Under normal conditions aluminum does not react from concentrated sulfuric acid due to passivation - formation of a dense oxide film. When heated, the reaction goes, formed sulfur oxide (IV), aluminum sulfateand water:
2AL + 6H 2 SO 4 (conc.) → Al 2 (SO 4) 3 + 3SO 2 + 6H 2 O
2.4. Aluminum does not react with concentrated nitric acid Also because of passivation.
FROM diluted nitric acid Aluminum reacts to the formation of molecular nitrogen:
10Al + 36hno 3 (Ravy) → 3N 2 + 10AL (NO 3) 3 + 18H 2 O
When the aluminum interacts in the form of a powder with very diluted nitric acid may form ammonium nitrate:
8AL + 30HNO 3 (Och.) → 8AL (NO 3) 3 + 3NH 4 NO 3 + 9H 2 O
2.5. Aluminum - amphoterous metal, so it interacts with alkalis . When interacting aluminum with solution Alkali is formed tetrahydroxyaluluminat. and hydrogen:
2AL + 2NAOH + 6H 2 O → 2NA + 3H 2
Videopy The interactions of aluminum with alkali and water can be viewed.
Aluminum reacts S. melt Alkali with education aluminate and hydrogen:
2AL + 6NAOH → 2NA 3 ALO 3 + 3H 2
The same reaction can be written in another form (I recommend writing the reaction in this form in this form):
2AL + 6NAOH → Naalo 2 + 3H 2 + Na 2 O
2.6. Aluminum restores Less active metals from oxides . The process of restoration of metals from oxides is called alumertemia .
for example , aluminum displaces copperof Copper oxide (II).The reaction is very exothermic:
Yet example : Aluminum restores iron of iron Scale, iron oxide (II, III):
8Al + 3Fe 3 O 4 → 4Al 2 O 3 + 9Fe
Restorative properties Aluminum also appear when it interacts with strong oxidizing agents: sodium peroxide, nitrates and nitrite in an alkaline environment permanganats, chromium compounds (Vi):
2Al + 3NA 2 O 2 → 2NAALO 2 + 2NA 2 O
8Al + 3Kno 3 + 5KOH + 18H 2 O → 8k + 3NH 3
10Al + 6kmno 4 + 24h 2 SO 4 → 5Al 2 (SO 4) 3 + 6mnso 4 + 3k 2 SO 4 + 24H 2 O
2Al + Nano 2 + NaOH + 5H 2 O → 2NA + NH 3
AL + 3KMNO 4 + 4KOH → 3K 2 MNO 4 + K
4Al + K 2 Cr 2 O 7 → 2CR + 2Kalo 2 + Al 2 O 3
Aluminum is a valuable industrial metal that is first recycled. Learn more about the reception of aluminum for processing, as well as current prices for this type of metal. .
Aluminium oxide
Methods for getting
Aluminium oxidecan be obtained by various methods:
1. Align Aluminum in the air:
4Al + 3O 2 → 2Al 2 O 3
2. Decomposition aluminum hydroxidewhen heated:
3. Aluminum oxide can be obtained decomposition of aluminum nitrate :
Chemical properties
Aluminum oxide - typical amphoteric oxide . Interacts with acid and main oxides, acids, alkalis.
1. With the essence of aluminum oxide with the main oxides Soli aluminata.
for example , alumina oxide oxide sodium:
Na 2 O + Al 2 O 3 → 2naalo 2
2. Aluminium oxide interact Wherein in melt Form sololi.—aluminatesa B. solution - complex salts . In this case, aluminum oxide shows acid Properties.
for example , alumina oxide sodium hydroxide In the melt with education aluminate sodium and water:
2NAOH + Al 2 O 3 → 2NAALO 2 + H 2 O
Aluminium oxide dissolves in excess alkaliswith education tetrahydroxalulumita:
Al 2 O 3 + 2NAOH + 3H 2 O → 2NA
3. Aluminum oxide does not interact with water.
4. Aluminum oxide interacting acid oxide (strong acids). At the same time are formed sololi. Aluminum. In this case, aluminum oxide shows basic properties.
for example , aluminum oxide interacts with sulfur oxide (VI) with education aluminum sulfate:
Al 2 O 3 + 3SO 3 → Al 2 (SO 4) 3
5. Aluminum oxide interacts with soluble acids with education medium and sour salts.
for example sulfuric acid:
Al 2 O 3 + 3H 2 SO 4 → Al 2 (SO 4) 3 + 3H 2 O
6. Aluminum oxide shows weak oxidative properties .
for example , aluminum oxide reacts with calcium hydride with education aluminum, hydrogen and calcium oxide:
Al 2 O 3 + 3CAH 2 → 3CAO + 2AL + 3H 2
Electricity restores Oxide aluminum (aluminum production):
2AL 2 O 3 → 4Al + 3O 2
7. Aluminum oxide is solid, non-volatile. And therefore he displaces more volatile oxides (usually carbon dioxide) from salt When fusing.
for example , out of sodium carbonate:
Al 2 O 3 + Na 2 CO 3 → 2NAALO 2 + CO 2
Aluminum hydroxide
Methods for getting
1. Aluminum hydroxide can be obtained by a solution ammonia on the aluminum salts.
for example , Aluminum chloride reacts with an aqueous solution of ammonia with education aluminum hydroxide and ammonium chloride:
AlCl 3 + 3NH 3 + 3H 2 O \u003d Al (OH) 3 + 3NH 4 Cl
2. Broadcast carbon dioxide, sulfur gas or serovodorod. through a solution of sodium tetrahydroxalumuta:
Na + CO 2 \u003d Al (OH) 3 + Nanco 3
To understand how this reaction proceeds, it is possible to use a simple reception: mentally divide the complex substance Na into components: NaOH and Al (OH) 3. Next, we define how carbon dioxide reacts with each of these substances, and write the products of their interaction. Because Al (OH) 3 does not react with CO 2, then we record the Al (OH) 3 on the right unchanged.
3. Aluminum hydroxide can be obtained by action. lack of alkali on the excess salt aluminum.
for example, aluminum chloridereacts S. disadvantage of potassium hydroxidewith education aluminum hydroxideand Chloride potassium:
ALCL 3 + 3KOH (unfortunate) \u003d Al (OH) 3 ↓ + 3KCL
4. Also, aluminum hydroxide is formed when soluble interaction salts aluminum with soluble carbonates, sulfites and sulfides . Sulphides, carbonates and aluminum sulfites in aqueous solution.
For example: bromide aluminum Reacts S. sodium carbonate. At the same time, the precipitate of aluminum hydroxide falls out, carbon dioxide is distinguished and sodium bromide is formed:
2Albr 3 + 3NA 2 CO 3 + 3H 2 O \u003d 2AL (OH) 3 ↓ + CO 2 + 6NABR
Aluminum chloride Reacts S. sodium sulfide With the formation of aluminum hydroxide, hydrogen sulfide and sodium chloride:
2ALCL 3 + 3NA 2 S + 6H 2 O \u003d 2AL (OH) 3 + 3H 2 S + 6NACL
Chemical properties
1. Aluminum hydroxide reacts with soluble acids . At the same time are formed medium or acidic salts, depending on the ratio of reagents and the type of salt.
for example nitric acid with education aluminum nitrate:
Al (OH) 3 + 3HNO 3 → AL (NO 3) 3 + 3H 2 O
Al (OH) 3 + 3HCl → ALCL 3 + 3H 2 O
2AL (OH) 3 + 3H 2 SO 4 → Al 2 (SO 4) 3 + 6H 2 O
AL (OH) 3 + 3HBR → ALBR 3 + 3H 2 O
2. Aluminum hydroxide interacts with acid oxide of strong acids .
for example , aluminum hydroxide interacts with sulfur oxide (VI) with education aluminum sulfate:
2AL (OH) 3 + 3SO 3 → Al 2 (SO 4) 3 + 3H 2 O
3. Aluminum hydroxide interact with soluble bases (alkalis).Wherein in melt Form sololi.—aluminatesa B. solution - complex salts . At the same time, aluminum hydroxide shows acid Properties.
for example , hydroxide aluminumInterates with potassium hydroxidein the melt with education aluminate potassiumand water:
2KOH + Al (OH) 3 → 2Kalo 2 + 2H 2 O
Aluminum hydroxide dissolves in excess alkaliswith education tetrahydroxalulumita:
Al (OH) 3 + KOH → K
4. G.idroxide Aluminum decomposewhen heated:
2AL (OH) 3 → Al 2 O 3 + 3H 2 O
Videopy Aluminum hydroxide interactions with hydrochloric acid and alkalis (Amphoteric properties of aluminum hydroxide) can be viewed.
Aluminum salts
Aluminum nitrate and sulfate
Nitrate Aluminumwhen heated decomposes on aluminium oxide, nitrogen oxide (IV) and oxygen:
4Al (NO 3) 3 → 2AL 2 O 3 + 12NO 2 + 3O 2
Aluminum sulfate with severe heating decomposes similarly - on aluminium oxide, sulphur dioxide and oxygen:
2AL 2 (SO 4) 3 → 2AL 2 O 3 + 6SO 2 + 3O 2
Comprehensive salts of aluminum
To describe the properties of complex salts of aluminum - hydroxyaluluminatesIt is convenient to use the following method: mentally scatter the tetrahydroxyalummate into two separate molecules - alumina hydroxide and alkali metal hydroxide.
for example , sodium tetrahydroxalulum is divided into aluminum hydroxide and sodium hydroxide:
Na.we smash on NaOH and Al (OH) 3
Properties of the entire complex can be determined as the properties of these individual compounds.
Thus, aluminum hydroxocomplexes react with acid oxide .
for example , hydroxacomplex is destroyed under the action of excess carbon dioxide. At the same time, with CO 2, NaOH reacts to the formation of an acidic salt (with an excess of CO 2), and the amphoteric hydroxide of aluminum does not react to carbon dioxide, therefore, it is precipitated:
Na + CO 2 → AL (OH) 3 ↓ + NaHCO 3
Similarly, potassium tetrahydroxalulum reacts with carbon dioxide:
K + CO 2 → AL (OH) 3 + KHCO 3
By the same principle of tetrahydroxalulums reacts with sulfur gas SO 2:
Na + SO 2 → Al (OH) 3 ↓ + NaHSO 3
K + SO 2 → Al (OH) 3 + KHSO 3
But under the action excess of severe acid the precipitate does not fall out, because Amphoteric aluminum hydroxide reacts with strong acids.
for example , from hydrochloric acid:
Na + 4HCl (excess) → NaCl + AlCl 3 + 4H 2 O
True, under the action of a small amount ( disadvantage ) severe acid The precipitate still falls, for dissolving aluminum hydroxide, the acid will not be enough:
Na + HCl (disadvantage) → AL (OH) 3 ↓ + NaCl + H 2 O
Similarly with disadvantage nitric acid Aluminum hydroxide drops:
Na + HNO 3 (disadvantage) → AL (OH) 3 ↓ + Nano 3 + H 2 O
Complex collapsed when coaching with chlorine water (chlorine aqueous solution) Cl 2:
2NA + CL 2 → 2AL (OH) 3 ↓ + NaCl + Naclo
At the same time chlorine disprbiones.
Also the complex can react with excess aluminum chloride. At the same time, aluminum hydroxide precipitate falls:
ALCL 3 + 3NA → 4AL (OH) 3 ↓ + 3NACL
If you evaporate water from a complex salt and heat the sampled substance, then the usual salt-aluminate will remain:
Na → Naalo 2 + 2H 2 O
K → Kalo 2 + 2H 2 O
Hydrolysis of aluminum salts
Soluble aluminum and strong acid salts hydrolyzed by cation. Hydrolysis proceeds step and reversible. a little bit:
Stage I: Al 3+ + H 2 O \u003d Aloh 2+ + H +
II Step: ALOH 2+ + H 2 O \u003d AL (OH) 2 + + H +
III Step: AL (OH) 2 + + H 2 O \u003d Al (OH) 3 + H +
but sulfides, sulphites, carbonates aluminum and them sour sololi. Hydrolyzed irreversible, fully. in aqueous solution do not exist, and water decompose:
Al 2 (SO 4) 3 + 6NAHSO 3 → 2AL (OH) 3 + 6SO 2 + 3NA 2 SO 4
2Albr 3 + 3NA 2 CO 3 + 3H 2 O → 2AL (OH) 3 ↓ + CO 2 + 6NABR
2AL (NO 3) 3 + 3NA 2 CO 3 + 3H 2 O → 2AL (OH) 3 ↓ + 6Nano 3 + 3CO 2
2AlCl 3 + 3NA 2 CO 3 + 3H 2 O → 2AL (OH) 3 ↓ + 6NACL + 3CO 2
Al 2 (SO 4) 3 + 3K 2 CO 3 + 3H 2 O → 2Al (OH) 3 ↓ + 3CO 2 + 3K 2 SO 4
2AlCl 3 + 3NA 2 S + 6H 2 O → 2AL (OH) 3 + 3H 2 S + 6NACL
Aluminata
Salts in which aluminum is an acid residue (aluminates) - are formed from aluminum oxide for fusion with alkalis and main oxides:
Al 2 O 3 + Na 2 O → 2naalo 2
To understand the properties of aluminates, they are also very convenient to smash into two separate substances.
For example, sodium aluminate we are divided into two substances mentally: aluminum oxide and sodium oxide.
Naalo 2. We smash on Na 2 O and Al 2 O 3
Then we will be obvious that aluminates react with acids with the formation of aluminum salts :
Kalo 2 + 4HCl → KCL + AlCl 3 + 2H 2 O
Naalo 2 + 4HCl → AlCl 3 + NaCl + 2H 2 O
Naalo 2 + 4HnO 3 → AL (NO 3) 3 + Nano 3 + 2H 2 O
2Naalo 2 + 4H 2 SO 4 → Al 2 (SO 4) 3 + Na 2 SO 4 + 4H 2 O
Under the action of excess water, the aluminates go into complex salts:
Kalo 2 + H 2 O \u003d K
Naalo 2 + 2H 2 O \u003d Na
Binary compounds
Aluminum sulfide Under the action of nitric acid is oxidized to sulfate:
Al 2 S 3 + 8hno 3 → Al 2 (SO 4) 3 + 8NO 2 + 4H 2 O
either to sulfuric acid (under the action hot lesy acid):
Al 2 S 3 + 30hno 3 (conc. Mountains.) → 2Al (NO 3) 3 + 24NO 2 + 3H 2 SO 4 + 12H 2 O
Aluminum sulfide decomposes water:
Al 2 S 3 + 6H 2 O → 2al (OH) 3 ↓ + 3H 2 s
Aluminum carbide Also decomposed with water when heated to aluminum hydroxide and methane:
Al 4 C 3 + 12H 2 O → 4Al (OH) 3 + 3CH 4
Aluminum nitride decomposes under action mineralic acids on salts of aluminum and ammonium:
ALN + 4HCL → ALCL 3 + NH 4 Cl
Also aluminum nitride decomposes under the action water:
Aln + 3H 2 O → Al (OH) 3 ↓ + NH 3
Aluminum oxide - Al2O3. Physical properties:aluminum oxide - white amorphous powder or very solid white crystals. Molecular weight \u003d 101.96, density - 3.97 g / cm3, Melting point - 2053 ° C, Boiling point - 3000 ° C.
Chemical properties:aluminum oxide shows amphoteric properties - the properties of acidic oxides and the main oxides and reacts with acids, and with bases. Crystal AL2O3 is chemically passive, amorphous - more active. Interaction with acid solutions gives middle salts of aluminum, and with solutions of bases - complex salts - metal hydroxy aluminates:
When fusing aluminum oxide with solid alkali metals, double salts are formed - metalüminata(anhydrous aluminates):
Aluminum oxide does not interact with water and does not dissolve in it.
Getting:aluminum oxide is obtained by recovery by aluminum metals from their oxides: chromium, molybdenum, tungsten, vanadium, etc. - metalothermiaOpen Beketov:
Application:aluminum oxide is used for the production of aluminum, in the form of a powder - for refractory, chemically resistant and ab-operating materials, in the form of crystals - for the manufacture of lasers and synthetic gems (rubies, sapphires, etc.), painted oxides of other metals - CR2O3 ( Red color), Ti2O3 and Fe2O3 (blue color).
Aluminum hydroxide - A1 (OH) 3. Physical properties:aluminum hydroxide is white amorphous (gel) or crystalline. Almost not soluble in water; Molecular weight - 78.00, density - 3.97 g / cm3.
Chemical properties:typical amphoteric hydroxide reacts:
1) with acids, forming medium salts: Al (it) 3 + 3NO3 \u003d Al (NO3) 3 + 3N2O;
2) with alkali solutions, forming complex salts - hydroxyalulums: Al (it) 3 + Kone + 2N2O \u003d K.
When solving Al (OH) 3, metalulumages are formed with dry alkalis: Al (it) 3 + Kon \u003d kalo2 + 2N2O.
Getting:
1) from aluminum salts under the action of alkalis solution: ALSL3 + 3NAOH \u003d AL (OH) 3 + 3N2O;
2) decomposition of aluminum nitride with water: Aln + 3N2O \u003d AL (OH) 3 + NN3?;
3) transmitting CO2 through a hydroxamplex solution: [AL (OH) 4] - + CO2 \u003d AL (OH) 3 + NSO3-;
4) action on solo alto hydrate ammonia; At room temperature, AlL (OH) 3 is formed.
62. General characteristics of the chromium subgroup
Elements subgroups chromiumoccupy an intermediate position in a number of transitional metals. Have high melting and boiling temperatures, free places on electronic orbitals. Elements chromiumand molybdenumpossess an atypical electronic structure - on the outer S-orbital have one electron (like NB from the VB subgroup). These elements on external D- and S-orbitals are 6 electrons, so all orbitals are filled with half, i.e., each is located one electron. Having a similar electronic configuration, the element has special stability and resistance to oxidation. Tungstenhas a stronger metal communication than molybdenum. The degree of oxidation in the elements of the chromium subgroup varies greatly. Under the proper conditions, all elements exhibit a positive degree of oxidation from 2 to 6, the maximum degree of oxidation corresponds to the number of the group. Not all the degrees of oxidation at the elements are stable, the chromium is the most stable - +3.
All elements form MVIO3 oxide, oxides with lower degrees of oxidation are also known.All elements of this subgroup of amphoterns are formed complex compounds and acids.
Chrome, Molybdenumand tungstenin demand in metallurgy and electrical engineering. All the considered metals are coated with a passivating oxide film when storing in air or in an oxidizing agent medium. Removal film with a chemical or mechanical method can increase the chemical activity of metals.
Chromium.The element is obtained from the FE chromite ore (CRO2) 2, restoring coal: Fe (CRO2) 2 + 4C \u003d (Fe + 2CR) + 4Co?.
Pure chrome is obtained by the restoration of CR2O3 using aluminum or electrolysis of a solution containing chromium ions. Having chromium with electrolysis, a chrome coating used as decorative and protective films can be obtained.
From chromium is obtained by ferrochrome, used in the production of steel.
Molybdenum.Get from sulfide ore. Its compounds are used in steel production. Metal itself is obtained when restoring its oxide. Giving molybdenum oxide with iron, you can get ferromolibdden. Use for the manufacture of threads and tubes for winding furnaces and electrocontacts. Steel with the addition of molybdenum is used in automotive production.
Tungsten.Get from oxide extracted from enriched ore. Aluminum or hydrogen is used as a reducing agent. The resulting tungsten in the idea of \u200b\u200bpowder is subsequently molded at high pressure and thermal processing (powder metallurgy). In this form, tungsten are used for the manufacture of incandescent threads, added to steel.
Aluminum hydroxide is a chemical, which is a compound of aluminum oxide with water. May be in liquid and solid states. Liquid hydroxide is an incremental transparent substance that is very poorly dissolved in water. The solid hydroxide is a white crystalline substance that has passive chemical properties and does not respond to virtually no other element or compound.
Obtaining aluminum hydroxide
The preparation of aluminum hydroxide is due to the chemical exchange reaction. To do this, use an aqueous solution of ammonia and any salt of aluminum, most often aluminum chloride. Thus, a liquid substance is obtained. If a solid hydroxide is needed, a carbon dioxide is passed through the solid alkali of the tetrahydroxodacodyumuminate. Many fans of experiments are concerned about how to get aluminum hydroxide at home? To do this, it is enough to purchase the necessary reagents and chemical dishes in a specialized store.
To obtain a solid, it will also be necessary for special equipment, so it is better to stay on the liquid version. When carrying out the reaction, it is necessary to use a well-ventilated room, since one of the by-products can be a gas or a substance with a sharp smell, which can negatively affect the well-being and human health. It is worth working in special protective gloves, since most acids are chemical burns when entering the skin. It will not be superfluous to take care of the protection for the eyes in the form of special glasses. Getting Started to any case, first of all it is necessary to think about ensuring security!
Fresh-insulated aluminum hydroxide reacts with most active acids and alkalis. That is why it is used to prepare ammonium water to preserve the formed substance in its pure form. When used to obtain an acid or alkali, it is necessary to accurately calculate the proportion of the elements, otherwise, with an excess, the aluminum hydroxide interacts with the remnants of an uncomplicated base and completely dissolves in it. This is due to the high level of chemical activity of aluminum and its connections.
Basically, aluminum hydroxide is obtained from bauxite ore with a high metal oxide content. The procedure allows you to quickly and relatively cheaply separate the useful elements from the empty breed. The reactions of aluminum hydroxide with acids lead to the restoration of salts and water formation, and with alkalis - to the preparation of complex hydroxaluminum salts. The solid hydroxide by the method of oscillates is combined with solid alkalis with the formation of metalulumages.
The main properties of the substance
The physical properties of aluminum hydroxide: density - 2,423 grams per centimeter Cubic, the level of solvent in water is low, the color is white or transparent. The substance may exist in four polymorphic versions. Under the influence of low temperatures, alpha hydroxide is formed, called bayerite. Under the influence of heating, gamma hydroxide or gibbsite can be obtained. Both substances have a crystalline molecular grille with hydrogen intermolecular bond types. Two more modifications are also found - beta hydroxide or nordandard and triclinic glex. The first is obtained by calcining Bayerit or Gibbsita. It differs from the other types of triclinic, and not the monotonous structure of the crystal lattice.
Chemical properties of aluminum hydroxide: the molar mass - 78 mol, in liquid state is well soluble in active acids and alkalis, when heated is decomposed, it has amphoteric signs. In industry in the overwhelming majority of cases, it is liquid hydroxide, since due to the high level of chemical activity, it is easily processing and does not require the use of catalysts or special conditions for the reaction flow.
Amphoterity of aluminum hydroxide is manifested in the duality of its nature. This means that under various conditions, it can exhibit acidic or alkaline properties. When hydroxide takes part in the reaction as alkali, a salt is formed, in which aluminum is a positively charged cation. Speaking as an acid, aluminum hydroxide at the output also forms salt. But in this case, the metal already plays the role of a negatively charged anion. Dual nature opens up ample opportunities for the use of this chemical compound. It is used in medicine for the manufacture of drugs appointed by impaired acid-alkaline balance in the body.
Aluminum hydroxide is part of vaccines as a substance that enhances the body's immune response to an irritant. The insoluability of the precipitate of aluminum hydroxide in water allows the use of substance in water treatment purposes. The chemical compound is a very strong adsorbent, which allows you to extract a large number of harmful elements from the water.
Application in industry
The use of hydroxide in industry is associated with obtaining pure aluminum. The technological process begins with the processing of ore containing aluminum oxide, which, upon completion of the process, goes into hydroxide. The output of products in this reaction is quite high, so after completion there is almost a nude breed. Next, the decomposition of aluminum hydroxide is carried out.
The procedure does not require special conditions, since the substance is well decomposed when heated to a temperature above 180 degrees Celsius. This stage allows you to select aluminum oxide. This compound is a basic or auxiliary material for the manufacture of a large amount of industrial and household products. If it is necessary to obtain pure aluminum, the electrolysis process is used with the addition of sodium cryolate. The catalyst takes oxygen from oxide, and pure aluminum settles on the cathode.
