Aluminum oxide AL 2 O 3 (alumina) is the most important connection of aluminum. In its pure form, a white very refractory substance, has several modifications, of which the crystalline is the most resistant - AL 2 O 3 and amorphous y - Ал 2 O 3. In nature is found in the form of various breeds and minerals.

Of the important properties of AL 2 O 3, the following should be noted:

1) very solid (inferior only to diamond and some boron compounds);

2) Amorphous AL 2 O 3 has high surface activity and water absorbing property - an effective adsorbent;

3) has high catalytic activity, especially widely used in organic synthesis;

4) Used as a carrier of catalysts - nickel, platinum, etc.

By chemical properties of AL 2 O 3 is a typical amphoteric oxide.

In water, it does not dissolve and does not interact with it.

I. dissolved in acids and alkalis:

1) AL 2 O 3 + 6HCl \u003d 2ALCL 3 + ZN 2 O

Al 2 O 3 + 6N + \u003d 2AL 3+ + zn 2 o

2) AL 2 O 3 + 2NAOH + ZN 2 O \u003d 2NA

AL 2 O 3 + 20N - + ZN 2 O \u003d 2 [AL (OH) 4] -

II. Film with solid alkalis and metal oxides, forming anhydrous metaaluminda:

A 2 O 3 + 2CON \u003d 2KALO 2 + H 2 O

A 2 O 3 + MGO \u003d Mg (ALO) 2

Methods for obtaining AL 2 O 3

1. Extract from natural bauxite.

2. The combustion of AL powder in oxygen current.

3. Thermal decomposition Al (OH) 3.

4. Thermal decomposition of some salts.

4Al (NO 3) 3 \u003d 2AL 2 O 3 + 12NO 2 + 3O 2

5. Aluminothermia, for example: Fe 2 O 3 + 2Al \u003d Al 2 O 3 + 2fe

Aluminum hydroxide Al (OH) 3 is a solid colorless substance insoluble in water. When heated decomposes:

2AL (OH) 3 \u003d Al 2 O 3 + zn 2 o

Al 2 O 3 obtained by this method is called aluminum.

By chemical properties - typical amphoteric hydroxide, dissolves in acids, and alkalis:

Al (OH) 3 + 3HCl \u003d alsl 3 + zn 2 p

Al (OH) 3 + NaOH \u003d Na Tetrahydroxal Sodium

When solving Al (OH) 3, metalulumages are formed with solid alkalis - ALO metagideroxide salts (O), which can be considered as salts of metaaluminic acid NO 2:

AL (OH) 3 + NaOH \u003d Naalo 2 + 2N 2 O

Aluminum salts

Due to the amphoterity of aluminum hydroxide and the possibility of its existence in ortho and metaofam, there are various types of salts. Since Al (OH) 3 shows very weak acid and very weak basic properties, all types of salts in aqueous solutions are strongly susceptible to hydrolysis, as a result of which the insoluble Al (OH) 3 is ultimately formed. The presence in an aqueous solution of one or another type of aluminum salts is determined by the size of the pH of this solution.

1. Al 3+ salts with anions of strong acids (AlCl 3, Al 2 (SO 4) 3, Al (NO 3) 3, ALVR 3) exist in acidified solutions. In the neutral medium, metalulumages containing aluminum in the composition of anion ALO 2 exist in a solid state. Distributed in nature. When dissolved in water, hydroxyaluminates are converted.

2. Hydro-aluminum containing aluminum as part of anion - exist in alkaline solutions. In the neutral medium heavily hydrolyzed.

3. Metalüminates containing aluminum as part of anion ALO 2. There are solid states. Distributed in nature. When dissolved in water, hydroxyaluminates are converted.

Mutual aluminum salts are described by the scheme:

Ways to precipitate (obtain) AL (OH) 3 of solutions of its salts

I. The deposition of solutions containing Al 3+ salts:

Al 3+ + zones - \u003d ал (OH) 3 ↓

a) action of strong alkalis added without excess

ALSL 3 + 3NAOH \u003d AL (OH) 3 ↓ + zn 2 o

b) the effect of aqueous solutions of ammonia (weak base)

ALSL 3 + 3NH 3 + ZN 2 O \u003d AL (OH) 3 ↓ + 3NH 4 Cl

c) the effect of salts of very weak acids, the solutions of which due to hydrolysis have an alkaline environment (excess it -)

2Alsl 3 + 3NA 2 CO 3 + 3N 2 O \u003d AL (OH) 3 ↓ + SSO 2 + 6NACL

Al 2 (SO 4) 3 + 3K 2 S + 6N 2 O \u003d 2AL (OH) 3 ↓ + 3K 2 SO 4 + 3H 2 S

II. Deposition of solutions containing hydroxyalulums:

[AL (OH) 4] - + H + \u003d AL (OH) 3 ↓ + H 2 O

a) action of strong acids added without excess

Na [AL (OH) 4] + HCl \u003d AL (OH) 3 ↓ + NaCl + H 2 O

2 [AL (OH) 4] + H 2 SO 4 \u003d 2AL (OH) 3 ↓ + Na 2 SO 4 + 2N 2 O

b) the effect of weak acids, for example, transmitting from 2

Na [AL (OH) 4] + CO 2 \u003d AL (OH) 3 ↓ + NAHCO 3

III. Deposition as a result of reversible or irreversible hydrolysis of Al 3+ salts (enhanced by diluting the solution with water and when heated)

a) reversible hydrolysis

Al 3+ + H 2 O \u003d Al (OH) 2+ + H +

AL 3+ + 2N 2 O \u003d AL (OH) 2 + 2H +

AL 3+ + 3H 2 O \u003d AL (OH) 3 + + 3H +

b) irreversible hydrolysis

Al 2 S 3 + 6H 2 O \u003d 2Al (OH) 3 ↓ + 3H 2 S

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 - properties acid oxides and main oxides and react 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 mass - 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.

Hydroxide aluminum

Chemical properties

Chemical formula of aluminum hydroxide: Al (OH) 3. This is a chemical compound of aluminum oxide with water. Synthesized in the form of a white jelly-like substance, which is poorly soluble in water. Hydroxide has 4 crystalline modifications: nordstranit (β), monoclinic (γ) gibbsit, bayerite (Γ) and hydragilite. There is also an amorphous substance, the composition of which varies: Al2O3 NH2O.

Chemical properties. The connection manifests amphoteric properties. Aluminum hydroxide reacts with alkalis: when reactions with sodium hydroxide In solution is obtained Na (Al (OH) 4); When fusing substances, water is formed and Naalo2.. And heating is observed decomposition of aluminum hydroxide to water and aluminum oxide . The substance does not react with the solution ammonia . The reaction of aluminum plus sodium hydroxide : 2AL + 2NAOH + 6H2O \u003d 2NA + 3H2.

Obtaining aluminum hydroxide. Chemical compound They are obtained from alley salts when they interact with an aqueous solution of alkali in a disadvantage, avoiding excess. TO chlorida Aluminum Alcl3. Adjust sodium hydroxide - As a result, the required substance falls in the form of a white sediment and additionally formed sodium chloride .

The agent can also be obtained by reaction by a water-soluble aluminum salt with an alkali metal carbonate. For example, K. chlorida Aluminum add sodium carbonate and water - as a result we get sodium chloride , carbon dioxide and al. hydroxide .

Application:

• used for water purification as an adsorbent;
• you can synthesize aluminum sulfate When the alcohol and alcohols interact sulfuric acid ;
• as an adjuvant in the manufacture of a vaccine;
• in medicine in the form antacid ;
• in the manufacture of plastic and other materials in the form of the suppressor of burning processes.

pharmachologic effect

Antacid adsorbing, enveloping.

Pharmacodynamics and pharmacokinetics

Aluminum hydroxide neutralizes hydrochloric acid, decomposing it on aluminum chloride and water. The substance gradually increases pH Gastric juice up to 3-4.5 and retains at this level for several hours. The acidity of the gastric juice is significantly reduced, its proteolytic activity is oppressed. When penetrating into an intestine alkaline medium, the means forms chlorine ions and phosphates that are not absorbed, ions Cl. Subjected to reabsorption.

Indications for use

The medicine is used:

• for the treatment of a 12-risk and stomach;
• with chronic at normal and elevated secretory functions of the stomach during exacerbation;
• during therapy gryzhi esophageal hole diaphragm;
• to eliminate discomfort and painful sensations in the area of \u200b\u200bthe stomach;
• when drinking alcohol, coffee or nicotine, some drugs;
• in case of non-compliance with the diet.

Contraindications

The tool cannot be taken:

• patients with;
• with serious kidney diseases.

Side effects

After taking aluminum hydroxide, adverse reactions are rarely developed. Most likely the appearance. The probability of side action can be reduced, if you additionally accept.

Instructions for use (method and dosage)

Aluminum hydroxide is prescribed for intake. The medicine is most often taken in the form of a suspension, with a concentration of the active component of 4%. As a rule, they take 1 or 2 teaspoons of the drug, 4 or 6 times a day. The duration of treatment depends on the disease and recommendations of the doctor.

Overdose

There are no data on overdose.

Interaction

When combining the drug with trisilicate magnesium An antacid optimization is observed and the congestion effect of the drug from heartburn is reduced.

special instructions

Special caution is observed in the treatment of patients with violations of phosphoric exchange.

Aluminum hydroxide, characteristics, properties and reception, chemical reactions.

Aluminum hydroxide - inorganic substance, It has 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:

* Note:

- there is no data.

Obtaining aluminum hydroxide:

Aluminum hydroxide is obtained as a result of the following chemical reactions:

1. 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 solutions Rychochi, avoiding their excess.

1. 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 carbonate alkali metals.

Chemical properties of aluminum hydroxide. Chemical reactions of aluminum hydroxide:

Aluminum hydroxide has amphoteric properties, i.e. possesses both basic 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 metagideroxide, 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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Aluminum - element of the 13th (III) group periodic table Chemical elements with atomic number 13. It is indicated by the Al symbol. Refers to a group of light metals. The most common metal and the third prevalence chemical element in earth Kore (after oxygen and silicon).

Aluminium oxide Al2O3. - In nature is common as alumina, white refractory powder, hardness is close to diamond.

Aluminum oxide is a natural compound, can be obtained from bauxite or thermal decomposition of aluminum hydroxides:

2AL (OH) 3 \u003d Al2O3 + 3H2O;

Al2O3 is amphoteric oxide, chemically inert, due to its durable crystal lattice. It does not dissolve in water, does not interact with acid solutions and alkalis and can react only with molten alkali.

About 1000 ° C intensively interacts with alkali and alkali metal carbonates to form aluminates:

Al2O3 + 2KOH \u003d 2KALO2 + H2O; Al2O3 + Na2CO3 \u003d 2NAALO2 + CO2.

Other Al2O3 forms are more active, can react with acid solutions and alkalis, α-Al2O3 interacts only with hot concentrated solutions: Al2O3 + 6HCl \u003d 2ALCl3 + 3H2O;

Amphoteric properties of aluminum oxide are manifested by interacting with acid and main oxides to form salts:

Al2O3 + 3SO3 \u003d Al2 (SO4) 3 (basic properties), Al2O3 + Na2O \u003d 2NAALO2 (acid properties).

Aluminum hydroxide, Al (OH) 3- Compound aluminum oxide with water. White student substance, poorly soluble in water, has amphoteric properties. Receive with the interaction of aluminum salts with aqueous solutions: AlCl3 + 3NAOH \u003d Al (OH) 3 + 3NACL

Aluminum hydroxide - a typical amphoteric compound, freshly cooled hydroxide dissolves in acids and alkalis:

2AL (OH) 3 + 6HCl \u003d 2AlCl3 + 6H2O. Al (OH) 3 + NaOH + 2H2O \u003d Na.

When heated decomposes, the dehydration process is quite complicated and schematically be represented as follows:

Al (OH) 3 \u003d aloh + h2o. 2ALOOH \u003d Al2O3 + H2O.

Aluminata - Salts formed under the action of a pitch to fresh aluminum hydroxide: AL (OH) 3 + NaOH \u003d Na (sodium tetrahydroxalulum)

Aluminates are also obtained by dissolving metal aluminum (or Al2O3) in alkalis: 2Al + 2NAOH + 6N2O \u003d 2NA + ZN2

Hydroxyaluluminates They are formed by the interaction of Al (OH) 3 with an excess of alkali: Al (OH) 3 + NaOH (HA) \u003d Na

Aluminum salts. Aluminum hydroxide can be obtained from almost all aluminum salts. Almost all aluminum salts are well soluble in water; The phosphate aluminum is poorly dissolved in water.
In the solution of aluminum salts, they show the acid reaction. An example is a reversible exposure to water chloride of aluminum:
AlCl3 + 3N2O "AL (OH) 3 + 3NSL
Many aluminum salts have practical importance. So, for example, anhydrous aluminum chloride ALSL3 is used in chemical practice as a catalyst for oil processing
Al2 aluminum sulfate (SO4) 3 18H2O is used as a coagulant when cleaning tap water, as well as in paper production.
Double aluminum salts are widely used - KAL (SO4) 2 12H2O, Naal (SO4) 2 12H2O, NH4AL (SO4) 2 12H2O, etc. - have strong astringent properties and are used when taking skin, as well as in medical practice as a hemostatic agent.

Application- Due to the properties complex, the thermal equipment is widespread in thermal equipment. - Aluminum and its alloys retain strength at ultra-low temperatures. Due to this, it is widely used in cryogenic technique. - Aluminum is the perfect material for the manufacture of mirrors. - In the production of building materials as a gas-forming agent. - Alitization gives corrosive and scale resistance to steel and other alloys, - aluminum sulfide is used to produce hydrogen sulfide. - Research on Development of foam aluminum as a particularly durable and lightweight material.

As a reducing agent- as a component of termitic, mixtures for altertermia - in pyrotechnics. - Aluminum is used to restore rare metals from their oxides or halides. (Aluminothermia)

Aluminothermia.- A method of obtaining metals, non-metals (as well as alloys) with the restoration of their metal aluminum oxides.