Ammonia


Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the formula. 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 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.

Etymology

The name ammonia is derived from the name of the Egyptian deity Amun since priests and travelers of those temples would burn soils rich in ammonium chloride, which came from animal dung and urine. Pliny, in Book XXXI of his Natural History, refers to a salt named hammoniacum, so called because of the proximity of its source to the Temple of Jupiter Amun in the Roman province of Cyrenaica. However, the description Pliny gives of the salt does not conform to the properties of ammonium chloride. According to Herbert Hoover's commentary in his English translation of Georgius Agricola's De re metallica, it is likely to have been common sea salt. In any case, that salt ultimately gave ammonia and ammonium compounds their name.
Substances containing ammonia, or those that are similar to it, are called ammoniacal.

Natural occurrence (abiological)

Ammonia is found throughout the Solar System on Earth, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto, among other places: on smaller, icy bodies such as Pluto, ammonia can act as a geologically important antifreeze, as a mixture of water and ammonia can have a melting point as low as if the ammonia concentration is high enough and thus allow such bodies to retain internal oceans and active geology at a far lower temperature than would be possible with water alone.

Atmospheric occurrence

Ammonia arises in the atmosphere from both anthropogenic and natural sources. The prevalent source is agriculture at around 80%. This includes fertilizers, urea produced by livestock, and manure in order of contribution. Biomass burning also contributes to atmospheric ammonia, with forest fires and agricultural waste burning emitting roughly the same amount of ammonia into the atmosphere. Ammonia can be emitted naturally from soils and plants when the concentration of ammonia in the soil or plant is higher than the concentration of ammonia in the air. This is known as one part of the bi-directional exchange model.
The dominant sink for atmospheric ammonia is rain. In soil, ammonia-oxidizing archaea and ammonia-oxidizing bacteria convert ammonia into nitrite. The atmospheric lifetime of ammonia through these processes vary from 12 to 48 hours.

Reactions of atmospheric ammonia

Atmospheric ammonia gives sulfate-nitrate aerosols through reactions with sulfuric acid and nitric acid, with ammonium sulfate being prominent in this process due to its low vapor pressure. These aerosols affect the climate and can impact [|human health]. Atmospheric ammonia can also be oxidized itself by the hydroxyl radical:
The lifetime of ammonia through oxidization is much longer than through deposition, with it being as low as 30 days. The amino radical then can be oxidized by multiple compounds to form greenhouse gases such as nitrous oxide. The oxidation of ammonia may also result in the production of nitric oxide, increasing NOx levels significantly in rural areas where relative levels are typically lower compared to urban areas.

Properties

Ammonia is a colourless gas with a characteristically pungent smell. It is lighter than air, its density being 0.589 times that of air. It is easily liquefied due to the strong hydrogen bonding between molecules. Gaseous ammonia turns to a colourless liquid, which boils at, and freezes to colourless crystals at. Little data is available at very high temperatures and pressures, but the liquid-vapor critical point occurs at 405 K and 11.35 MPa.

Solid

The crystal symmetry is cubic, Pearson symbol cP16, space group P213 No.198, lattice constant 0.5125 nm.

Liquid

ammonia possesses strong ionising powers reflecting its high ε of 22 at. Liquid ammonia has a very high standard enthalpy change of vapourization and can be transported in pressurized or refrigerated vessels; however, at standard temperature and pressure liquid anhydrous ammonia will vaporize.

Solvent properties

Ammonia readily dissolves in water. In an aqueous solution, it can be expelled by boiling. The aqueous solution of ammonia is basic, and may be described as aqueous ammonia or ammonium hydroxide. The maximum concentration of ammonia in water has a specific gravity of 0.880 and is often known as '.880 ammonia'.
Temperature
Density
Specific heat
Kinematic
viscosity
Thermal
conductivity
Thermal
diffusivity
Prandtl
Number		Bulk modulus
−50703.694.4634.35×10−70.5471.74×10−72.6
−40691.684.4674.06×10−70.5471.78×10−72.28
−30679.344.4763.87×10−70.5491.80×10−72.15
−20666.694.5093.81×10−70.5471.82×10−72.09
−10653.554.5643.78×10−70.5431.83×10−72.07
0640.14.6353.73×10−70.5401.82×10−72.05
10626.164.7143.68×10−70.5311.80×10−72.04
20611.754.7983.59×10−70.5211.78×10−72.022.45×10−3
30596.374.893.49×10−70.5071.74×10−72.01
40580.994.9993.40×10−70.4931.70×10−72
50564.335.1163.30×10−70.4761.65×10−71.99

Temperature
Temperature Density
Specific heat
Dynamic
viscosity
Kinematic
viscosity
Thermal
conductivity
Thermal
diffusivity
Prandtl
Number
273−0.150.79292.1779.35×10−61.18×10−50.02201.31×10−50.90
32349.850.64872.1771.10×10−51.70×10−50.02701.92×10−50.88
37399.850.5592.2361.29×10−51.30×10−50.03272.62×10−50.87
423149.850.49342.3151.47×10−52.97×10−50.03913.43×10−50.87
473199.850.44052.3951.65×10−53.74×10−50.04674.42×10−50.84
480206.850.42732.431.67×10−53.90×10−50.04924.74×10−50.822
500226.850.41012.4671.73×10−54.22×10−50.05255.19×10−50.813
520246.850.39422.5041.80×10−54.57×10−50.05455.52×10−50.827
540266.850.37952.541.87×10−54.91×10−50.05755.97×10−50.824
560286.850.37082.5771.93×10−55.20×10−50.06066.34×10−50.827
580306.850.35332.6132.00×10−55.65×10−50.06386.91×10−50.817

Liquid ammonia is a widely studied nonaqueous ionising solvent. Its most conspicuous property is its ability to dissolve alkali metals to form highly coloured, electrically conductive solutions containing solvated electrons. Apart from these remarkable solutions, much of the chemistry in liquid ammonia can be classified by analogy with related reactions in aqueous solutions. Comparison of the physical properties of with those of water shows has the lower melting point, boiling point, density, viscosity, dielectric constant and electrical conductivity. These differences are attributed at least in part to the weaker hydrogen bonding in. The ionic self-dissociation constant of liquid at −50 °C is about 10−33.
Solubility
Ammonium acetate253.2
Ammonium nitrate389.6
Lithium nitrate243.7
Sodium nitrate97.6
Potassium nitrate10.4
Sodium fluoride0.35
Sodium chloride157.0
Sodium bromide138.0
Sodium iodide161.9
Sodium thiocyanate205.5

Liquid ammonia is an ionising solvent, although less so than water, and dissolves a range of ionic compounds, including many nitrates, nitrites, cyanides, thiocyanates, metal cyclopentadienyl complexes and metal bisamides. Most ammonium salts are soluble and act as acids in liquid ammonia solutions. The solubility of halide salts increases from fluoride to iodide. A saturated solution of ammonium nitrate contains 0.83 mol solute per mole of ammonia and has a vapour pressure of less than 1 bar even at. However, few oxyanion salts with other cations dissolve.
Liquid ammonia will dissolve all of the alkali metals and other electropositive metals such as Ca, Sr, Ba, Eu and Yb. At low concentrations, deep blue solutions are formed: these contain metal cations and solvated electrons, free electrons that are surrounded by a cage of ammonia molecules.
These solutions are strong reducing agents. At higher concentrations, the solutions are metallic in appearance and in electrical conductivity. At low temperatures, the two types of solution can coexist as immiscible phases.