Ammonia (NH₃) — Properties, Uses & Safety

Overview

Ammonia (NH3) is a colorless gas with a sharp, pungent odor that is instantly recognizable — it is the smell of smelling salts and many household cleaners. With a molar mass of 17.03 g/mol, ammonia is one of the most important industrial chemicals and the most produced synthetic chemical compound in the world. Its molecular structure is trigonal pyramidal with a bond angle of approximately 107°, slightly less than the tetrahedral angle due to the lone pair of electrons on nitrogen. This lone pair makes ammonia a Lewis base and gives it the ability to form hydrogen bonds, explaining its high solubility in water and relatively high boiling point (-33 °C) for such a small molecule. Ammonia is produced industrially by the Haber-Bosch process (N2 + 3 H2 ⇌ 2 NH3), which combines atmospheric nitrogen with hydrogen gas at high temperature (400-500 °C) and high pressure (150-300 atm) using an iron catalyst. This process, developed by Fritz Haber and Carl Bosch in the early 1900s, is arguably the most important chemical reaction in human history — it enabled the mass production of nitrogen fertilizers that now support food production for roughly half of the world's population. Both Haber and Bosch received Nobel Prizes for this work. The primary use of ammonia (about 80%) is in fertilizer production, either directly as anhydrous ammonia or as the precursor to urea, ammonium nitrate, and ammonium phosphate fertilizers. Other uses include production of nitric acid (via the Ostwald process), manufacture of explosives, refrigeration (as a coolant), household cleaning products, and production of synthetic fibers like nylon. In nature, ammonia is produced by the decomposition of organic matter and is part of the nitrogen cycle. Safety considerations include its toxicity at high concentrations (it is corrosive to the respiratory tract and eyes), its flammability in certain concentration ranges, and its environmental impact when released into waterways (causing eutrophication). GHS pictograms include the corrosion, gas cylinder, skull and crossbones, and environment symbols. For chemistry students, ammonia is a treasure trove of learning: it illustrates VSEPR theory and molecular geometry, Lewis base behavior, hydrogen bonding, chemical equilibrium and Le Chatelier's principle (the Haber process is the classic example), industrial chemistry, and the nitrogen cycle. Understanding ammonia connects classroom chemistry to global food security.

IUPAC Name

azane

CAS Number

7664-41-7

PubChem CID

222

Molecular Formula

NH₃

Molar Mass

17.031 g/mol

State at STP

gas

Appearance

Colorless gas with pungent odor