Ammonia

Introduction

Ammonia is a 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 characteristic pungent smell. It is a common nitrogenous waste, particularly among aquatic organisms, and it contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers.

Properties

Ammonia is a compound with a trigonal pyramidal shape, a shape that would be impossible to achieve with a simple, linear arrangement of the three hydrogen atoms and the nitrogen atom. The nitrogen atom in the molecule has a lone electron pair, which makes ammonia a base, a proton acceptor. This shape gives the molecule a dipole moment and makes it polar. This polarity allows it to form hydrogen bonds, and makes it highly soluble in water.

A photograph of a 3D model of an ammonia molecule, showing one nitrogen atom (blue) and three hydrogen atoms (white) arranged in a trigonal pyramidal shape.

Production and synthesis

Ammonia is naturally produced in the nitrogen cycle and also synthetically, most commonly through the Haber process. This process involves the direct reaction of nitrogen gas and hydrogen gas under conditions of high temperature and pressure in the presence of a metal catalyst. The Haber process produces up to 450 million tonnes of ammonia annually.

Uses

Ammonia is used in numerous areas, including the production of fertilizers, cleaning products, and industrial applications. It is also used in the production of nitric acid, which is a precursor for the synthesis of many explosives, and in various pharmaceutical applications.

Health and safety

Ammonia is both caustic and hazardous in its concentrated form and can cause burns to the skin and eyes. Inhalation of ammonia can cause respiratory distress or failure. However, the widespread use of ammonia means that it is commonly found in low concentrations, which are not harmful to humans.

Environmental impact

Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. However, excess ammonia can lead to a host of negative environmental impacts, including eutrophication of aquatic systems, acidification of soils, and contributing to the formation of fine particulate matter in the atmosphere.