Ammonia is a compound that is the most important source of nitrogen for living organisms, as well as found application in various industries. What is ammonia, what are its properties? Let's figure it out.
What is ammonia: main characteristics
Ammonia (hydrogen nitride) is a nitrogen compound with hydrogen having the chemical formula NH 3 . The shape of the molecule resembles a trigonal pyramid, at the top of which there is a nitrogen atom.
Ammonia is a gas that has no color but has a sharp specific odor. The density of ammonia is almost half that of air. At a temperature of 15 o C it is 0.73 kg / m 3 . The density of liquid ammonia under normal conditions is 686 kg / m 3 . The molecular weight of the substance is 17.2 g / mol. A distinctive feature of ammonia is its high solubility in water. So, at a temperature of 0 ° C its value reaches about 1200 volumes in the volume of water, at 20 ° C - 700 volumes. The ammonia-water solution (ammonia water) is characterized by a slightly alkaline reaction and a rather unique property compared to other alkalis: with increasing concentration, the density decreases.
How is ammonia formed?
What is ammonia in the human body? This is the end product of nitrogen metabolism. Liver converts most of it to urea (urea), a less toxic substance.
Ammonia under natural conditions is formed as a result of decomposition of organic compounds containing nitrogen. For industrial use, this substance is obtained artificially.
Ammonia production in industrial and laboratory conditions
In industrial conditions, ammonia is obtained by catalytic synthesis from nitrogen and hydrogen:
N 2 + 3H 2 → 2NH3 + Q.
The process of obtaining substances is carried out at a temperature of 500 ° C and a pressure of 350 atm. Porous iron is used as a catalyst . The resulting ammonia is removed by cooling. Nitrogen and hydrogen that have not reacted are returned to synthesis.
In laboratory conditions, ammonia is obtained mainly by slightly heating a mixture consisting of ammonium chloride and hydrated lime:
2NH 4 Cl + Ca (OH) 2 → CaCl 2 + 2NH 3 ↑ + 2H 2 O.
For drainage, the finished compound is passed through a mixture of lime and caustic soda. Pretty dry ammonia can be obtained by dissolving metallic sodium in it and subsequent distillation.
Where is ammonia used?
Hydrogen nitride is widely used in various industries. Its huge quantities are used for the production of nitric acid and various fertilizers (urea, ammonium nitrate, etc.), polymers, hydrocyanic acid, soda, ammonium salts and other types of chemical products.
In light industry, the properties of ammonia are used in the cleaning and dyeing of fabrics such as silk, wool and cotton. In the steel industry, it is used to increase the hardness of steel by saturating its surface layers with nitrogen. In the petrochemical industry, acid wastes are neutralized using hydrogen nitride.
Due to its thermodynamic properties, liquid ammonia is used as a refrigerant in refrigeration equipment.
A solution of hydrogen nitride (ammonia) is used in medicine to remove from a swoon, stimulate vomiting, to treat the hands of medical staff, with insect bites, etc.
Some chemical properties of ammonia
Hydrogen nitride is characterized by a fairly high chemical activity and is able to react with many substances.
In the interaction of ammonia with acids, the corresponding ammonium salts are formed. So, for example, as a result of a reaction with nitric acid, ammonium nitrate is formed :
NH 3 + HNO 3 → NH 4 NO 3.
When interacting with HCl, ammonium chloride is formed:
NH 3 + HCl → NH 4 Cl.
Ammonium salts are solid crystalline substances that decompose in water and have properties inherent to metal salts. Solutions of compounds formed as a result of the interaction of ammonia and strong acids have a slightly acid reaction.
Due to nitrogen atoms, hydrogen nitride is an active reducing agent. Its reducing properties are manifested when heated. When burned in an oxygen atmosphere, it forms nitrogen and water. In the presence of catalysts, reaction with oxygen gives nitric oxide. Hydrogen nitride has the ability to reduce metals from oxides.
Halogens as a result of reaction with ammonia form nitrogen halides - hazardous explosives. When interacting with carboxylic acids and their derivatives, hydrogen nitride forms amides. In reactions with coal (at 1000 ° C) and methane, it gives hydrocyanic acid.
With metal ions, ammonia forms aminocomplexes, or ammonia (complex compounds), which have a characteristic feature: the nitrogen atom is always bound to three hydrogen atoms. As a result of complexation, the color of the substance changes. So, for example, the blue solution of copper sulfate upon the addition of hydrogen nitride acquires an intense blue-violet color. Many of the amino complexes are sufficiently stable. Due to this, they can be obtained in solid form.
In liquid ammonia, both ionic and nonpolar inorganic and organic compounds dissolve well.
Sanitary characteristics
Ammonia is classified as a fourth hazard class. The maximum permissible maximum one-time concentration (MPC) in the air of settlements is 0.2 mg / m 3 , and the daily average is 0.04. In the air of the working area, the ammonia content should not be higher than 20 mg / m³. At such concentrations, the smell of the substance is not felt. It begins to be fixed by human smell at 37 mg / m³. That is, if the smell of ammonia is felt, this means that the permissible norms for the substance in the air are significantly exceeded.
Effects on the human body
What is ammonia in terms of human exposure? This is a toxicant. It is attributed to substances capable of exerting a choking and neurotropic effect, inhalation poisoning of which can lead to pulmonary edema and damage to the nervous system.
Ammonia fumes irritate the skin, mucous membranes of the eyes and respiratory organs. The concentration of the substance at which irritation of the pharynx is manifested is 280 mg per cubic meter. meter, eye - 490 mg per cubic meter meter. Depending on the amount of hydrogen nitride in the air, a sore throat, shortness of breath, coughing, eye pain, profuse lacrimation, chemical burn of the cornea, and vision loss may occur. With an ammonia content of 1.5 g per cubic meter. within an hour toxic pulmonary edema develops. Upon contact of liquid ammonia and its solutions (in high concentrations) with the skin, redness, itching, burning, and dermatitis are possible. Since liquefied hydrogen nitride absorbs heat during evaporation, frostbite of various degrees is possible.
Symptoms of Ammonia Poisoning
Poisoning with this toxicant can cause a decrease in the auditory threshold, nausea, dizziness, headache, etc. Changes in behavior are possible, in particular severe excitement, delirium. The manifestation of symptoms in some cases is intermittent. They can stop for a while, and then renew with renewed vigor.
Given all the possible consequences of exposure to ammonia, it is very important to observe safety precautions when working with this substance and not to allow its concentration in the air to be exceeded.