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Jai Ganesh

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Ammonia

Ammonia

Gist

Ammonia (NH3 is a colorless, pungent gas composed of nitrogen and hydrogen, commonly used in household cleaners and fertilizers. It is a natural byproduct in the human body from protein breakdown but can be toxic at high concentrations. Ammonia's properties include being highly soluble in water, having a strong odor, and being highly alkaline.  

Ammonia is used primarily in agriculture to make fertilizers, and also for industrial purposes like producing plastics, dyes, explosives, and synthetic fibers. It is also found in household products like glass and surface cleaners, and used in applications such as refrigeration and as a fuel for some rockets. 

Summary

Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the formula NH3. A stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pungent smell. It is widely used in fertilizers, refrigerants, explosives, cleaning agents, and is a precursor for numerous chemicals. Biologically, it is a common nitrogenous waste, and it contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to fertilisers. Around 70% of ammonia produced industrially is used to make fertilisers in various forms and composition, such as urea and diammonium phosphate. Ammonia in pure form is also applied directly into the soil.

Ammonia, either directly or indirectly, is also a building block for the synthesis of many chemicals. In many countries, it is classified as an extremely hazardous substance. Ammonia is toxic, causing damage to cells and tissues. For this reason it is excreted by most animals in the urine, in the form of dissolved urea.

Ammonia is produced biologically in a process called nitrogen fixation, but even more is generated industrially by the Haber process. The process helped revolutionize agriculture by providing cheap fertilizers. The global industrial production of ammonia in 2021 was 235 million tonnes. Industrial ammonia is transported by road in tankers, by rail in tank wagons, by sea in gas carriers, or in cylinders. Ammonia occurs in nature and has been detected in the interstellar medium.

Ammonia boils at −33.34 °C (−28.012 °F) at a pressure of one atmosphere, but the liquid can often be handled in the laboratory without external cooling. Household ammonia or ammonium hydroxide is a solution of ammonia in water.

Details

Ammonia (NH3) is a colourless, pungent gas composed of nitrogen and hydrogen. It is the simplest stable compound of these elements and serves as a starting material for the production of many commercially important nitrogen compounds.

Uses of ammonia

The major use of ammonia is as a fertilizer. In the United States, it is usually applied directly to the soil from tanks containing the liquefied gas. The ammonia can also be in the form of ammonium salts, such as ammonium nitrate, NH4NO3, ammonium sulfate, (NH4)2SO4, and various ammonium phosphates. Urea, (H2N)2C=O, is the most commonly used source of nitrogen for fertilizer worldwide. Ammonia is also used in the manufacture of commercial explosives (e.g., trinitrotoluene [TNT], nitroglycerin, and nitrocellulose).

In the textile industry, ammonia is used in the manufacture of synthetic fibres, such as nylon and rayon. In addition, it is employed in the dyeing and scouring of cotton, wool, and silk. Ammonia serves as a catalyst in the production of some synthetic resins. More important, it neutralizes acidic by-products of petroleum refining, and in the rubber industry it prevents the coagulation of raw latex during transportation from plantation to factory. Ammonia also finds application in both the ammonia-soda process (also called the Solvay process), a widely used method for producing soda ash, and the Ostwald process, a method for converting ammonia into nitric acid.

Ammonia is used in various metallurgical processes, including the nitriding of alloy sheets to harden their surfaces. Because ammonia can be decomposed easily to yield hydrogen, it is a convenient portable source of atomic hydrogen for welding. In addition, ammonia can absorb substantial amounts of heat from its surroundings (i.e., one gram of ammonia absorbs 327 calories of heat), which makes it useful as a coolant in refrigeration and air-conditioning equipment. Finally, among its minor uses is inclusion in certain household cleansing agents.

Preparation of ammonia

Pure ammonia was first prepared by English physical scientist Joseph Priestley in 1774, and its exact composition was determined by French chemist Claude-Louis Berthollet in 1785. Ammonia is consistently among the top five chemicals produced in the United States. The chief commercial method of producing ammonia is by the Haber-Bosch process, which involves the direct reaction of elemental hydrogen and elemental nitrogen.
N2 + 3H2 → 2NH3

This reaction requires the use of a catalyst, high pressure (100–1,000 atmospheres), and elevated temperature (400–550 °C [750–1020 °F]). Actually, the equilibrium between the elements and ammonia favours the formation of ammonia at low temperature, but high temperature is required to achieve a satisfactory rate of ammonia formation. Several different catalysts can be used. Normally the catalyst is iron containing iron oxide. However, both magnesium oxide on aluminum oxide that has been activated by alkali metal oxides and ruthenium on carbon have been employed as catalysts. In the laboratory, ammonia is best synthesized by the hydrolysis of a metal nitride.
Mg3N2 + 6H2O → 2NH3 + 3Mg(OH)2

Physical properties of ammonia

Ammonia is a colourless gas with a sharp, penetrating odour. Its boiling point is −33.35 °C (−28.03 °F), and its freezing point is −77.7 °C (−107.8 °F). It has a high heat of vaporization (23.3 kilojoules per mole at its boiling point) and can be handled as a liquid in thermally insulated containers in the laboratory. (The heat of vaporization of a substance is the number of kilojoules needed to vaporize one mole of the substance with no change in temperature.) The ammonia molecule has a trigonal pyramidal shape with the three hydrogen atoms and an unshared pair of electrons attached to the nitrogen atom. It is a polar molecule and is highly associated because of strong intermolecular hydrogen bonding. The dielectric constant of ammonia (22 at −34 °C [−29 °F]) is lower than that of water (81 at 25 °C [77 °F]), so it is a better solvent for organic materials. However, it is still high enough to allow ammonia to act as a moderately good ionizing solvent. Ammonia also self-ionizes, although less so than does water.

Additional Information

Ammonia is a colorless, poisonous gas with a familiar noxious odor. It occurs in nature, primarily produced by anaerobic decay of plant and animal matter; and it also has been detected in outer space. Some plants, mainly legumes, in combination with rhizobia bacteria, “fix” atmospheric nitrogen to produce ammonia.

Ammonia has been known by its odor since ancient times. It was isolated in the 18th century by notable chemists Joseph Black (Scotland), Peter Woulfe (Ireland), Carl Wilhelm Scheele (Sweden/Germany), and Joseph Priestley (England). In 1785, French chemist Claude Louis Berthollet determined its elemental composition.

Ammonia is produced commercially via the catalytic reaction of nitrogen and hydrogen at high temperature and pressure. The process was developed in 1909 by German chemists Fritz Haber and Carl Bosch. Both received the Nobel Prize in Chemistry for their work, but in widely separated years: Haber in 1918 and Bosch in 1931. The fundamental Haber–Bosch process is still in use today.

In 2020, the worldwide ammonia production capacity was 224 million tonnes (Mt). Actual production was 187 Mt. It ranks ninth among chemicals produced globally.

Most ammonia production—≈85%—is used directly or indirectly in agriculture. Chemical fertilizers made from ammonia include urea, ammonium phosphate, ammonium nitrate, and other nitrates. Other important chemicals produced from ammonia include nitric acid, hydrazine, cyanides, and amino acids.

Ammonia was once used widely as a refrigerant. It has largely been displaced by chlorofluorocarbons and hydrochlorofluorocarbons, which are also under environmental scrutiny. Probably the most familiar household use of ammonia is in glass cleaners.

Ammonia is highly soluble in water; its exact solubility depends on temperature. Aqueous ammonia is also called ammonium hydroxide, but that molecule cannot be isolated. When ammonia is used as a ligand in coordination complexes, it is called “ammine”.

Currently ammonia is made from fossil fuel–derived hydrogen and is therefore not a “green” product, despite its widespread use in agriculture. But environmentally green ammonia may be on the horizon if the hydrogen is made by other means, such as wind- or solar-powered electrolysis of water.

Ammonia can be burned as a fuel in standard engines. A study by the catalyst company Haldor Topsoe (Kongens Lyngby, Denmark) concluded that replacing conventional ship fuels with green ammonia would be cost-efficient and would eliminate a significant source of greenhouse gases. It potentially can be used in aircraft fuels as well. During a transition period, ammonia could be mixed with conventional fuels.

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