[Chemistry Class Notes] on Ammonia Pdf for Exam

Ammonia is a pungent and colorless substance, which is composed of nitrogen and hydrogen. It is one of the simplest stable compounds of these elements, and it serves as a starting material for the formation of several commercially essential nitrogen compounds.

The chemical formula of ammonia is given as NH3.

Structure

The ammonia molecule contains a trigonal pyramidal shape, which is predicted by the VSEPR theory – Valence Shell Electron Pair Repulsion with an experimentally described bond angle of 106.7°. The central nitrogen atom contains 5 outer electrons, including an additional electron from every hydrogen atom. This gives a complete set of four electron pairs of eight electrons that are arranged tetrahedrally. Three of these electron pairs are used as bond pairs, which leave a single lone pair of electrons.

The lone pair repel more strongly compared to the bond pairs; thus, the bond angle is not as expected, 109.5°, for a regular tetrahedral arrangement, but it is 106.7°. This specific shape gives the molecule a dipole moment and makes it polar.

[]

Industrial Production of Ammonia

Industrially, the global production of ammonia in 2018 was listed as 175 million tonnes, with zero significant change relative to 2013’s global industrial production, which is given as 175 million tonnes. Industrial ammonia is sold either in the form of ammonia liquor (generally 28% of ammonia in water) or as refrigerated or pressurized anhydrous liquid ammonia, which is transported in cylinders or tank cars.

NH3 boils at a temperature of −33.34 °C  and at a pressure of one atmosphere, and because of that, the liquid should be stored at low temperature or under pressure. hydroxide or Household ammonia is a solution of NH3 in water. Such concentrated solutions are measured in the Baumé scale units (density), with 26 degrees of Baumé (by weight – about 30% ammonia at 59.9 °F or 15.5 °C) being a typical high-concentration commercial product.

Etymology

Pliny, in a book, refers to a salt produced in the Roman province of Cyrenaica named hammoniacum, so-called due to its proximity to the nearby Temple of Jupiter Amun. However, the description given by Pliny on salt does not conform to the ammonium chloride properties. According to the commentary of Herbert Hoover in his English translation of Georgius Agricola’s De re Metallica, it is more likely to have been common sea salt. Ultimately, in any case, that salt gave ammonium and ammonia compounds their name.

Natural Occurrence

Ammonia can be found chemically in trace quantities in nature, being formed from nitrogenous vegetable and animal matter. Both ammonium and ammonia salts are also found in the fewer quantities in rainwater, whereas ammonium sulfate and ammonium chloride (sal ammoniac) are found in volcanic districts; ammonium bicarbonate crystals have been found in the Patagonia guano. The kidneys secrete ammonia in excess acid neutralization. Ammonium salts can also be found distributed in seawater and through fertile soil.

Amphotericity

The most characteristic properties of ammonia are given as its basicity and is considered to be a weak base. It also combines with acids to produce salts; hence with hydrochloric acid, it forms ammonium chloride, ammonium nitrate, nitric acid, etc. Perfectly dry ammonia will not always combine with perfectly dry hydrogen chloride. Moisture is required to bring about the reaction. Opened bottles of the concentrated hydrochloric and ammonia acid produce clouds of ammonium chloride as a demonstration experiment, which seems to appear “out of nothing” because the salt produces where the two diffusing clouds of molecules meet, at some point between the two bottles.

NH3 + HCl → NH4Cl

The salts, which are produced by the ammonia action on acids, are called ammonium salts, and all contain ammonium ion (NH4+).

Formation of Other Compounds

In organic chemistry, ammonia acts as a nucleophile in substitution reactions. Amines are formed by the ammonia with alkyl halide reaction, although the resulting -NH₂ group is nucleophilic, and the secondary, tertiary amines are often resulting as byproducts. An ammonia excess helps to minimize the multiple substitutions and neutralizes the formed hydrogen halide. 

Methylamine can be commercially prepared by the ammonia with chloromethane reaction, and the ammonia with 2-bromopropanoic acid reaction has been used to prepare the racemic alanine in the yield of 70%. Ethanolamine can be prepared by a ring-opening reaction with ethylene oxide, which sometimes, the reaction is allowed to proceed further to form “di” and triethanolamine.

Ammonia as a Ligand

Ammonia acts as a ligand in the transition metal complexes. In the middle of the spectrochemical series, it is a pure σ-donor and exhibits intermediate hard-soft behavior. The relative donor strength of this acid toward a series of acids versus other Lewis bases can be illustrated by the C-B plots. For historical reasons, ammonia is named as ammine in the coordination compound’s nomenclature.

A few notable ammine complexes are given as tetraamminediaquacopper (II), with the chemical formula [Cu(NH3)4(H2O)2]2+), which is a dark blue complex formed by adding ammonia to a copper(II) salt solution.