Ammonia, preparation, properties, and chemical reactions.
Ammonia, NH3 is a chemical compound of nitrogen and hydrogen, consisting of one atom of nitrogen and three atoms of hydrogen nitride, hydrogen.
Ammonia – a chemical compound of nitrogen and hydrogen, consisting of one atom of nitrogen and three atoms of hydrogen nitride, hydrogen.
Ammonia (NH3) is the most simple and stable compound of nitrogen and hydrogen.
The chemical formula of ammonia NH3. Isomers has not.
The structure of the ammonia molecule:
The shape of the ammonia molecule resembles a trigonal pyramid, the top of which is a nitrogen atom. Three unpaired p-electron of the nitrogen atom involved in the formation of polar covalent bonds with the 1s electron of three hydrogen atoms (N−H), the fourth pair of outer electrons is unshared, it can form a covalent bond at the donor-acceptor mechanism with the hydrogen ion forming the ammonium ion NH4+. A non-binding two-electron cloud, strictly oriented in space, so the ammonia molecule has a high polarity, which leads to its good solubility in water.
Ammonia – under normal conditions is a colorless gas with a sharp characteristic smell (the smell of “ammonia”).
Ammonia – a toxic fuel is a gaseous substance having a property to form when in contact with air an explosive mixture.
Ammonia is a flammable gas. Flammable and explosive. In pure oxygen, ammonia burns with a pale yellow flame, turning mainly into nitrogen and water. Ammonia burns in the presence of a permanent source of fire. The presence of oils and other fuel increases the fire and explosion hazards this substance.
Ammonia forms with air an explosive mixture. Concentration limits of flame propagation – 15,0-33,6 volume fraction, %; or 107-240 g/m3. The most flammable concentration of 24.5% (180 g/m3).
It is soluble in water as in gaseous, and liquid. The solubility of NH3 in water is extremely high – about 1,200 volumes (at 0 °C) or 700 volumes (at 20 °C) in the amount of water. Upon dissolution of the ammonia in the water a significant amount of heat.
Aqueous ammonia solution has a strong alkaline reaction due to the formation of ammonium hydroxide NH4OH.
Ammonia refers to toxic substances, to the IV class of hazard (low hazard substances) according to GOST 12.1.007. MPC of ammonia in the atmospheric air of populated areas according to GOST 6221-90 are: maximum single 0.2 mg/m3; average – 0,04 mg/m3. Maximum permissible concentration in the working area of industrial premises (Pdcr.s. C.) according to GOST 12.1.005-88 is 20 mg/m3. The smell of ammonia exceeding the limits, because the smell of ammonia is felt at concentration of 37 mg/m3.
Ammonia by physiological effect on the organism belongs to the group of substances suffocating and neurotropic action that would defeat the inhalation to cause toxic pulmonary edema and severe damage to the nervous system. Ammonia has both local and resorptive effect. Ammonia vapour irritates mucous membranes of eyes and respiratory system, and skin. Liquid ammonia or a jet of gas, getting on the human skin, causes severe burns.
Ammonia in trace quantities in nature and the planets of the Solar system. Human kidneys secrete ammonia to neutralize excess acid.
Annual global industrial production of ammonia amounts to 180 million tons. It is one of the most important products of the chemical industry. Ammonia is produced in liquid form or in aqueous solution ammonia water, which usually contains 25% NH3.
Liquid ammonia is a colourless liquid, strongly refracting light.
Ammonia as a liquid is a good solvent for a very large number of organic and many inorganic compounds. In liquid ammonia is well soluble alkaline, alkaline earth metals, and other simple substances, such as phosphorus, iodine, sulphur. Poorly soluble in liquid ammonia nitrate, chloride and bromide salts, and salts of sulfuric, carbonic, acetic and phosphoric acids are usually insoluble.
Pure liquid ammonia is a dielectric, therefore capable of formation on the vessel walls by static electricity.
Liquefied anhydrous ammonia refers to nonflammable substances.
Liquid ammonia or a jet of gas, getting on the human skin, causes severe burns.
Solid ammonia apparently is negobrasil mass of cubic crystals of the correct form.
|The smell||with a sharp characteristic smell (the smell of “ammonia”)|
|Aggregate state (at 20 °C and atmospheric pressure of 1 ATM.)||gas|
|The density of liquid (at boiling point and atmospheric pressure 1 ATM.) kg/m3||682,8|
|Gas density (at boiling point and atmospheric pressure 1 ATM.) kg/m3||0,8886|
|Density (at 15 °C and atmospheric pressure of 1 ATM.) kg/m3||0,73|
|Density (at 25 °C and atmospheric pressure of 100 kPa ≈ 1 ATM.) kg/m3||0,7723|
|Melting point, °C||-77,73|
|Boiling point, °C||-33,34|
|Critical temperature*, °C||Of 132.4|
|Critical pressure, MPa||To 11.32|
|Critical specific volume, m3/kg||0,00426|
|Coefficient of thermal conductivity of gas (at 0 °C and atmospheric pressure of 1 ATM.) W/(m·K)||0,026|
|The auto-ignition temperature, °C||651 ± 1|
|Explosive concentration of the mixture of gas with air, % by volume||14.5 (15,0) up to 33.6|
|Explosive concentration of the mixture gas with oxygen, % bulk||from 13.5 to 82|
|Specific heat of combustion, MJ/kg||20,5|
|Flame temperature, °C||700|
|The dissociation constant of the acid||Of 9.21 ± 0,01|
|Molar mass, g/mol||17,0304|
* at temperatures above the critical temperature the gas cannot be condensed at any pressure.
The basic properties of ammonia due to the presence of unshared pairs of electrons of the nitrogen atom. The oxidation state of nitrogen in ammonia “-3” minimum. Therefore, in chemical terms ammonia is quite active: he enters in the reaction with many substances and shows only restorative properties.
For ammonia, characterized by the following chemical reaction:
1. the reaction between ammonia and water:
NH3 + H2O ⇄ NH3•H2O.
The reaction produced ammonia hydrate (NH3•H2O or NH4OН). A solution of ammonia in water has an alkaline environment.
NH3•H2O → NH3 + H2O (to).
When boiling hydrate of ammonia decomposes to form ammonia and water.
2. the reaction between ammonia and phosphoric acid:
NH3 + H3PO4 → NH4H2PO4.
The reaction produces ammonium dihydrogen phosphate.
Likewise, reactions of ammonia with other acids, with formation of ammonium salts.
3. the reaction between ammonia and oxygen – the combustion of ammonia:
4NH3 + 3O2 → 2N2 + 6H20.
The reaction produces nitrogen and water. The reaction is irreversible.
4. the reaction of catalytic oxidation of ammonia:
4NH3 + 5O2 → 4NO + 6H2O (kat = Pt, etc., t = 800 ° C);
NH3 + 2O2 → HNO3 + H2O (kat = Pt, Rh, t = 850 OS, p = 5 ATM.).
In the second reaction produce nitric acid and water. It is an industrial method of producing nitric acid. When the mixture of air with 10% (by volume) of ammonia is passed over a series of metal grids (platinum and 5-15% of rhodium) at a temperature of about 850 OS and a pressure of 5 ATM; the contact time with the catalyst is limited to ≤ 1 MS in order to minimize undesirable side reactions. The degree of conversion is about 96% (one of the most effective known industrial catalytic reactions); the vented gas is passed through the absorption column and get a 60% aqueous solution of nitric acid at 40°C. the Reaction proceeds in three stages.
5. the reaction between ammonia and copper oxide:
2NH3 + 3CuO → N2 + 3Cu + 3H2O (t = 500-550 oC).
6. the reaction of thermal decomposition of ammonia:
2NH3 ⇄ N2 + 3H2 (t = 1200-1300 OS).
The reaction produces nitrogen and hydrogen.
7. the reaction between ammonia and fluorine:
2NH3 + 3F2 → 6HF + N2 (t o).
The reaction formed hydrogen fluoride and nitrogen. Reaction occurs at high temperatures.
Likewise, reactions of ammonia with other Halogens.
8. the reaction of interaction of potassium oxide and ammonia:
K2O + NH3 → KNH2 + KOH (t = 50C).
The reaction formed potassium amide and potassium hydroxide. The reaction proceeds slowly in liquid ammonia.
Obtaining of ammonia in industry and the laboratory. The chemical reaction equation of producing ammonia:
Ammonia in the laboratory is the result of the following chemical reactions:
1. action of sodium hydroxide on ammonium chloride:
NH4Cl + NaOH → NH3 + NaCl + H2O.
The reaction produces gaseous ammonia, sodium chloride and water.
2. action of calcium hydroxide on ammonium sulfate:
(NH4)2SO4 + Ca(OH)2 → 2NH3 + CaSO4 + 2H2O.
The reaction produces gaseous ammonia, calcium sulphate and water.
3. action of calcium hydroxide on ammonium chloride:
NH4Cl + Ca(OH)2 → 2NH3 + CaCl2 + 2H2O.
The reaction produces gaseous ammonia, calcium chloride and water.
Thus, for obtaining the ammonia in the laboratory using the action of strong alkalis on ammonium salts.
Ammonia in industry is produced by direct interaction of hydrogen and nitrogen:
N2 + 3H2 ↔ 2NH3 (kat = porous iron with admixtures of Al2O3 and K2O, t = 500 ºc, p = 350 bar).
Due to the high pressure equilibrium of said reaction is shifted towards ammonia. This so-called Haber process. German physicist Fritz Haber, developed a physico-chemical basis of this method.
– in refrigeration as a refrigerant R717, R – Refrigerant (refrigerant), 7 – type of refrigerant (inorganic compound), 17 – molecular weight,
– in medicine as a lotion. 10 % aqueous solution of ammonia is known as ammonia,
– in the chemical industry for the production of nitrogen fertilizers (nitrate and ammonium sulphate, urea),
– as a raw material in the chemical industry for the production of explosives, polymers, nitric acid, soda (ammonia method), nylon, nylon and other chemical industry products
– liquid ammonia is used as solvent.
– in agriculture as fertilizer in the form of ammonia water.
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