What is the chemical formula for ammonia



Structural formula
General
Surname ammonia
other names
Molecular formula NH3
CAS number 7664-41-7[1] (Gas)
1336-21-6 (ammonium hydroxide)
Brief description Colorless, pungent smelling gas
properties
Molar mass 17 g mol−1
Physical state gaseous
density 0.7198 kg m−3[1]
Melting point −77.7 ° C[1]
boiling point −33 ° C[1]
Vapor pressure

8.5737 bar[1] (20 ° C)

pKa value

23

solubility

541 g l−1 in water (20 ° C)[1], readily soluble in alcohol, acetone, poorly in hexane

safety instructions
MAK

14 mg m−3[1]

LD50

350 mg kg−1

As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions.

ammonia is a chemical compound of nitrogen and hydrogen with the empirical formula NH3. It is named after the Ammonium saltAmmonium chloride from the Ammon's oasis, today Siwa oasis. Ammonia is a colorless and poisonous gas with a strong pungent smell that causes tears and is suffocating. The density of ammonia gas is less than the density of air. Ammonia is designated with the UN numbers 1005 (gaseous) or 2073 (aqueous solution).

Other properties


Ammonia is very soluble in water; 90.7 g (≙ 120 l) dissolve in 100 ml of water at 0 ° C. An ammonia solution is called salmiakgeist (ammonium hydroxide). It has an alkaline reaction. Ammonia has a pungent odor.

Ammonia-air mixtures are explosive in the range of 15.5 to 30% by volume of ammonia. On hot surfaces above 630 ° C it can decompose into nitrogen and hydrogen; this decomposition reaction is catalyzed by metals, so that in large-scale plants there is the possibility of explosive decomposition at surface temperatures from 300 ° C. It burns quickly and completely, so that afterwards there is no NH3 is more noticeable.

Ammonia has a corrosive effect on moist body surfaces. Moist skin, mucous membranes, lungs and eyes in particular are therefore corroded. If swallowed, it causes bloody vomiting with severe pain and if inhaled, it causes lung damage, possibly with fatal outcome. An ammonia content of 0.5% (5000 ppm) in the air is fatal after 30 to 60 minutes.

Acid-base properties

Ammonia is amphoteric and forms ionic ammonium salts as a base with protonation, and as an acid with strong bases it forms ionic amides with deprotonation. There is therefore an equilibrium in liquid ammonia that can be described by an ionic product.

structure

The ammonia molecule is not built flat, but corresponds to a three-sided pyramid (trigonal-pyramidal). It is derived from a tetrahedron in which the free (non-binding) electron pair of nitrogen occupies a corner. Due to the charge repulsion between the N – H bond electrons and the nitrogen lone pair of electrons, which also takes up space, the three hydrogen atoms are not in one plane with the nitrogen atom. In this way, the N – H bond electrons and the lone pair of electrons are as far apart as possible. Because of the higher electronegativity of nitrogen compared to hydrogen and because of the angulation, the molecule is polarized: there is a higher negative charge density in the vicinity of the lone pair of electrons. This is therefore the preferred target for electrophiles, for example H.+. The ammonia molecule is not rigid at room temperature. The lone pair of electrons can shift to the opposite side, whereby the hydrogen atoms also move to the other side. This caused the molecule to “swing through”, which can be clearly compared to folding down an umbrella. This property also applies to the compounds derived from ammonia (for example amines), provided they are not prevented from “swinging through” by the rigid geometry of the remaining molecule.

proof

Manufacturing

The production takes place today on an industrial scale for the most part (approx. 90% of world production) from hydrogen and nitrogen using the Haber-Bosch process.

Alternative manufacturing processes are extraction from calcium cyanamide (Rothe-Frank-Caro calcium cyanamide process) or by hydrolysis of nitrides (Serpek process).

Both processes are of no technical significance to speak of, since synthesis using the Haber-Bosch process is cheaper.

Another way of NH3- Generation is the reduction of nitrogen monoxide (NO) with hydrogen (H.2).

It can also be extracted from salmia salt (ammonium chloride) with sodium hydroxide solution (displacement reaction; at the same time detection reaction for ammonium salts)

use

Ammonia is one of the most important and common products in the chemical industry. Today the world annual production of ammonia is about 125 million tons. Around 3% of the energy produced worldwide is used for the production of ammonia. Most of this production is used as a raw material for nitrogen fertilizers. In addition:

  • Liquid ammonia is used in refrigeration machines because of its high heat of vaporization (refrigerant designation R717).
  • Ammonia is used in textile finishing, for plasticizing wood and as a non-aqueous solvent
  • Gaseous ammonia is used as a distraction agent.
  • In anhydrous, liquefied form, ammonia is used as a reagent and solvent for the Birch reduction in organic chemical synthesis.
  • In the metal industry, ammonia is used as ammonia cracking gas for nitriding and as a protective gas for heat treatment, also for bright annealing.
  • Ammonia water is used for cleaning and pickling purposes. It is also used to render chlorine and formaldehyde harmless after disinfection measures.
  • Ammonia can also be used to desulphurise flue gas. This forms ammonium sulphate, which is used as a fertilizer.
  • For a long time, concentrated ammonia (approx. 35% in water) was used to develop blueprints.
  • Ammonia is used for denitrification in both the flue gas cleaning of power plants and the exhaust gas cleaning of diesel engines (SCR process).
  • Ammonia is also used to make medicines and explosives.
  • Ammonia water is used in chlorine gas systems for leak testing. At leaks there is fog formation due to ammonium chloride [NH4Cl]
  • In liquid and supercritical form, it is becoming more and more important as a non-oxidative solvent, among other things because of its physical-chemical similarity to water (hydrogen bonds, self-dissociation 2NH3 → NH4+ + NH2, etc.)
  • Ammonia is produced by bacteria Helicobacter pylori produced in the stomach with the help of the enzyme urease from the urea contained in the stomach in order to neutralize the gastric acid and thus to be able to survive in the stomach. This bacterium is the number one cause of stomach ulcers.
  • Ammonia is one of the most important basic chemicals in the chemical industry. Numerous other preliminary products are made from it. The following are to be mentioned in particular:
ammonia _________ | ________________________________ | | | Oxidation | | all | (NH2)2CO (urea) further | / | organic nitric acid synthetic resins | and / / | | \ Fertilizers of inorganic nitrates / | | \ Nitrogen / | | \ / / | \ Fertilizers / | \ Hydroxylamine / | Nitriles / | \ / | / Adipic acid nitroaromatics amines hydrazine explosives \ aniline (derivatives)

swell

  1. abcdefG BGIA-Gestis hazardous substance database

literature

  • Robert Schlögl: Catalytic Ammonia Synthesis - A "Neverending Story"? Angewandte Chemie 115 (18), pp. 2050-2055 (2003), ISSN 0044-8249

Categories: Toxic Substance | Environmentally hazardous substance