Ammonia

Ammonia is a common nitrogenous waste, especially among aquatic organisms, and it contributes significantly to the nutritional requirements of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia is also a building block for the synthesis of many pharmaceutical products, either directly or indirectly, and is present in several commercial cleaning products.

What is Ammonia?

Ammonia (NH₃), is a component of nitrogen and hydrogen. It is a colourless and pungent gas. It is the simplest stable compound of these elements that help produce various commercially necessary nitrogen compounds as it serves as the starting material. Also, it is known as ammonium hydroxide in its aqueous form. The inorganic compound has a pungent smell. It is harmful and caustic when it is in the concentrated form.

Ammonia at STP is lighter than air with a density of 0.769 kg/m³. It’s commonly used as a fertilizer and also, in the production of explosives such as nitrocellulose and TNT. It is also useful in producing soda ash and the production of nitric acid in the Ostwald process.

Structure of Ammonia (NH₃)

Ammonia is a covalent atom, as the dot structure appears to be. Ammonia particle form by the overlap of three hydrogen orbitals and three hybrid sp₃ orbitals of N in the structure as the central atom. A single pair is involved in the fourth sp₃ hybrid orbital. It gives the ammonia particle a trigonal pyramid form. The bond edge of the H-N-H is 107.3°, which is not a tetrahedral edge of 109°28. It is because the bond pair-lone pair repulsions push the N-H bonds slightly inward. In solid and liquid states, ammonia bounds by hydrogen bonds.

Properties of Ammonia (NH₃)

• The chemical formula of ammonia is NH₃.
• Molecular Weight/ Molar Mass of the ammonia is 17.031 g/mol
• The density of ammonia is lighter than air, which is 0.73 kg/m^³
• It has a boiling point of -33.34 °C and melting point of -77.73 °C

Ammonia is known to act as a weak base because it mixes with several acids to become salt. For example, when reacted with hydrochloric acid, ammonia is converted to ammonium chloride. All the salts that form from such acid-base reactions are known to contain the NH₄+ ammonium cation. It is important to note that ammonia also exhibits weak acidic properties and can thus be considered an amphoteric compound.

The acidic properties of ammonia make it possible to form amides with some alkali metals and alkaline earth metals. An example of such a reaction is when lithium exposes itself to liquid ammonia it induces the formation of lithium amide (a chemical compound with the formula LiNH₂).

Note that the molecule of NH₃ undergoes self-dissociation when dissolved in water. The formation of its conjugate acid (NH₄+) and conjugate base (NH₂-) occurs when ammonia molecule goes under molecular autoionization.

The equilibrium reaction of the autoionization process is as follows:

/(2NH₃ \rightleftharpoons  NH₂– + NH₄+/)

As ammonia usually behaves as a relatively weak base, it can be useful for buffering purposes (for the control of pH changes).

Preparation of Ammonia

Before World War I, ammonia was mostly a product of the dry distillation process of nitrogenous vegetables and animal waste materials, such as camel dung. It undergoes distillation by reducing nitrous acid and nitrite with hydrogen. In fact, the production was by the distillation of coal, and also by the decomposition of ammonia salts by alkaline hydroxides such as quicklime:

\(2 NH_4Cl + 2 CaO \rightarrow  CaCl_2 + Ca(OH)_2 + 2 NH_3(g)\)

For small-scale laboratory synthesis, one can heat the urea along with calcium hydroxide:

\((NH_2)_2CO + Ca(OH)_2 \rightarrow CaCO_3 + 2 NH_3\)

Haber-Bosch Process

The mass production of ammonia primarily uses the Haber-Bosch process, a gas phase reaction between hydrogen (H₂) and nitrogen (N₂) at slightly elevated temperatures (450 °C) and high pressure (100 standard atmospheres (10 MPa))

\({N_2 + 3 H_2 \rightarrow 2 NH_3} \quad \Delta H^{\circ }=-91.8 {{kJ/mol}}\)

This process is both exothermic and results in reduced entropy, which means that the reaction is favourable at lower temperatures and higher pressures.

Natural Occurrence of Ammonia

Ammonia is a chemical present in trace amounts in nature that is derivative from nitrogenous animal wastes and vegetable matter. Ammonia and ammonium salts are also present in rainwater in minor concentrations, while ammonium chloride (sal ammoniac) and ammonium sulphate are abundant in the volcanic regions; ammonium bicarbonate crystals are present in the Patagonia guano. The kidneys secrete ammonia in order to neutralize the excess acid production. Ammonium salts spread through fertile soil and seawater.

Ammonia is also present throughout the Solar System on Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto, among others: on smaller, frozen bodies such as Pluto, ammonia can serve as a geologically significant antifreeze, as a combination of water and ammonia can have a melting point as low as 173K (−100 °C; −148 °F) If the concentration of ammonia is high enough and thereby allows these bodies to maintain internal oceans and active geology at a much lower temperature than would be possible for water alone. Ammonia-containing or similar substances are ammoniacal.

Uses of Ammonia

Ammonia is used:

• As a fertilizer for increasing the yield of crops.
• In the manufacturing of synthetic fabrics such as rayon and nylon.
• As cleaner in the household – NH₃ combined with water for washing stainless steel and glass.
• As fuel for rocket engines.
• In the fermentation in the industrial sector.
• As antimicrobial agents in food products.
• To neutralize pollutants such as nitrogen oxides produced by diesel engines.
• In the textile industry.
• As a pH adjuster during the fermentation process.

FAQs about Ammonia

Q.1. Where can ammonia be found naturally?

Answer. Ammonia can occur naturally in many parts of the environment, such as soil, air and vegetation. Also, note that the human body naturally generates ammonia which breaks down protein-containing food into amino acids. This ammonia later converts into urea. It is important to remember that ammonia and, by extension, ammonium ions are necessary components of many vital human metabolic processes.

Q.2. What are the side effects of ammonia inhalation?

Answer. When one inhales high amounts of ammonia, the most common symptoms include acute inflammation of the throat, nose, and respiratory tract. It may potentially lead to respiratory distress or respiratory failure. If the concentration of ammonia in the atmosphere is low, irritation of the throat and irritation of the nose are common side effects.

Q.3. What are the uses of ammonia?

Answer. There are several uses of ammonia. About 90% of ammonia production is useful in fertilizers to help sustain food production for billions of people across the world. Ammonia has other essential applications, for example, in household cleaning products and in the manufacture of other products.

Q.4. What does ammonia smell like?

Answer. Ammonia has a rather distinct, a pungent smell, described as similar to sweat or cat urine. Strong, brie-like cheeses can smell like ammonia, too. Cheeses also contain trace levels of ammonia in them as a natural by-product of the cheese ageing process.

Q.5. What are the chemical formula and molar mass of ammonia?

Answer. The chemical formula of ammonia is NH₃, and molar mass is 17.031 g/mol.