Ammonia

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For  NH+4, see  Ammonium. For other uses, see Ammonia (disambiguation).

Ammonia

Names

IUPAC name

Ammonia[1]

Systematic IUPAC name

Azane

Other names

Hydrogen nitride

R-717, R717 (refrigerant)

Identifiers

CAS Number  7664-41-7 

3D model  Interactive image

(JSmol)

3DMet  B00004

Beilstein 3587154
Reference

ChEBI  CHEBI:16134 

ChEMBL  ChEMBL1160819 

ChemSpider  217 

ECHA 100.028.760 

InfoCard

EC Number  231-635-3

Gmelin 79
Reference

KEGG  D02916 

MeSH Ammonia

PubChem CID  222

RTECS  BO0875000

number

UNII  5138Q19F1X 

UN number 1005

CompTox  DTXSID0023872 
Dashboard (EP
A)

show

InChI

show

SMILES

Properties

Chemical NH3
formula

Molar mass 17.031 g/mol 

Appearance Colourless gas

Odor strong pungent odour

Density 0.86 kg/m3 (1.013 bar at boiling point)

0.769  kg/m3 (STP)[2]

0.73 kg/m3 (1.013 bar at 15 °C)

681.9 kg/m3 at −33.3 °C (liquid)[3] See also Ammonia

 (data page)

817 kg/m3 at −80 °C (transparent solid)[4]

Melting point −77.73 °C (−107.91 °F; 195.42 K) (Triple point at

6.060 kPa, 195.4 K)

Boiling point −33.34 °C (−28.01 °F; 239.81 K)

Critical point ( 132.4 °C (405.5 K), 111.3 atm (11,280 kPa)

T, P)

Solubility in 47% w/w (0 °C)

water
31% w/w (25 °C)

18% w/w (50 °C)[5]

Solubility soluble in chloroform, ether, ethanol, methanol

Vapor pressure 857.3 kPa

Acidity (pKa) 32.5 (−33 °C),[6] 9,24 (of ammonium)

Basicity (pKb) 4.75

Conjugate acid Ammonium

Conjugate base Amide

Magnetic −18.0·10−6 cm3/mol
susceptibility (
χ)

Refractive 1.3327
index(nD)

Viscosity  10.07 µPa·s (25 °C)[7]

 0.276 mPa·s (−40 °C)

Structure

Point group C3v

Molecular Trigonal pyramid

shape

Dipole moment 1.42 D

Thermochemistry

Std molar 193 J·mol−1·K−1[8]

entropy (S o
298 )
Std enthalpy of −46 kJ·mol−1[8]
formation(ΔfH
⦵
298 )

Hazards

GHS labelling:[10]

Pictograms

   

Signal word Danger

Hazard H280, H314, H331, H410
statements

Precautionar P260, P273, P280, P303+P361+P353, P304+P340+P3
y statements
11, P305+P351+P338+P310

NFPA

704(fire diamo

nd)

3
1
0
COR

Flash point 132 °C (270 °F; 405 K)

Autoignition 651 °C (1,204 °F; 924 K)

temperature

Explosive 15,0–33,6%

limits

Lethal dose or concentration (LD, LC):

LD50 (media 0.015 mL/kg (human, oral)

n dose)

LC50 (media 40,300 ppm (rat, 10 min)

n
28,595 ppm (rat, 20 min)
concentratio
n) 20,300 ppm (rat, 40 min)

11,590 ppm (rat, 1 hr)

7338 ppm (rat, 1 hr)

4837 ppm (mouse, 1 hr)

 9859 ppm (rabbit, 1 hr)

9859 ppm (cat, 1 hr)

2000 ppm (rat, 4 hr)

4230 ppm (mouse, 1 hr)[9]

LCLo (lowest 5000 ppm (mammal, 5 min)

published)
5000 ppm (human, 5 min)[9]

NIOSH (US health exposure limits):[11]

PEL(Permis 50 ppm (25 ppm ACGIH- TLV; 35 ppm STEL)

sible)

REL(Recom TWA 25 ppm (18 mg/m3) ST 35 ppm (27 mg/m3)

mended)

IDLH (Imm 300 ppm

ediate
danger)

Safety data ICSC 0414 (anhydrous)

sheet(SDS)

Related compounds

Other cations Phosphine

Arsine

Stibine

Bismuthine

Related Hydrazine
nitrogen
Hydrazoic acid
hydrides

Related Ammonium hydroxide

compounds

Supplementary data page

Ammonia (data page)

Except where otherwise noted, data are given for materials in

their standard state (at 25 °C [77 °F], 100 kPa).
 verify (what is   ?)

Infobox references

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 distinct
pungent smell. Biologically, 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 45 percent of the world's food[12] and fertilizers. Ammonia, either
directly or indirectly, is also a building block for the synthesis of many pharmaceutical
products and is used in many commercial cleaning products. It is mainly collected by
downward displacement of both air and water.
Although common in nature—both terrestrially and in the outer planets of the Solar System
—and in wide use, ammonia is both caustic and hazardous in its concentrated form. In many
countries it is classified as an extremely hazardous substance, and is subject to strict reporting
requirements by facilities which produce, store, or use it in significant quantities.[13]
The global industrial production of ammonia in 2018 was 175 million tonnes,[14] with no
significant change relative to the 2013 global industrial production of 175 million tonnes.[15] In
2021 this was 235 million tonnes, with very little being made within the United States.[16]
[17]
 Industrial ammonia is sold either as ammonia liquor (usually 28% ammonia in water) or as
pressurized or refrigerated anhydrous liquid ammonia transported in tank cars or cylinders.[18]
NH3 boils at −33.34 °C (−28.012 °F) at a pressure of one atmosphere, so the liquid must be
stored under pressure or at low temperature. Household ammonia or ammonium hydroxide is
a solution of NH3 in water. The concentration of such solutions is measured in units of
the Baumé scale (density), with 26 degrees Baumé (about 30% (by weight) ammonia at
15.5 °C or 59.9 °F) being the typical high-concentration commercial product.[19]

Contents

 1Etymology
 2Natural occurrence
 3Properties
o 3.1Structure
o 3.2Amphotericity
o 3.3Self-dissociation
o 3.4Combustion
o 3.5Formation of other compounds
o 3.6Ammonia as a ligand
 4Detection and determination
o 4.1Ammonia in solution
o 4.2Gaseous ammonia
o 4.3Ammoniacal nitrogen (NH3-N)
 5History
 6Applications
o 6.1Solvent
o 6.2Fertilizer
o 6.3Precursor to nitrogenous compounds
o 6.4Cleansing agent
o 6.5Fermentation
o 6.6Antimicrobial agent for food products
o 6.7Other
o 6.8Toxicity
o 6.9Storage information
o 6.10Laboratory
o 6.11Laboratory use of anhydrous ammonia (gas or liquid)
 7Production
o 7.1Haber–Bosch
o 7.2Electrochemical
 8Role in biological systems and human disease
o 8.1Biosynthesis
 o 8.2Physiology
o 8.3Excretion
 9Beyond Earth
o 9.1Interstellar space
 10See also
 11Notes
 12References
o 12.1Works Cited
 13Further reading
 14External links

Etymology[edit]
Pliny, in Book XXXI of his Natural History, refers to a salt produced in the Roman province
of Cyrenaica named hammoniacum, so called because of its proximity to the nearby Temple
of Jupiter Amun (Greek Ἄμμων Ammon).[20] However, the description Pliny gives of the salt
does not conform to the properties of ammonium chloride. According to Herbert
Hoover's commentary in his English translation of Georgius Agricola's De re metallica, it is
likely to have been common sea salt.[21] In any case, that salt ultimately
gave ammonia and ammonium compounds their name.

Natural occurrence[edit]
Ammonia is a chemical found in trace quantities in nature, being produced from nitrogenous
animal and vegetable matter. Ammonia and ammonium salts are also found in small
quantities in rainwater, whereas ammonium chloride (sal ammoniac), and ammonium
sulfate are found in volcanic districts; crystals of ammonium bicarbonate have been found
in Patagonia guano.[22] The kidneyssecrete ammonia to neutralize excess acid.[23] Ammonium
salts are found distributed through fertile soil and in seawater.
Ammonia is also found throughout the Solar
System on Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto, among other places: on
smaller, icy bodies such as Pluto, ammonia can act as a geologically important antifreeze, as
a mixture of water and ammonia can have a melting point as low as 173 K (−100 °C;
−148 °F) if the ammonia concentration is high enough and thus allow such bodies to retain
internal oceans and active geology at a far lower temperature than would be possible with
water alone.[24][25] Substances containing ammonia, or those that are similar to it, are
called ammoniacal.

Properties[edit]
Ammonia is a colourless gas with a characteristically pungent smell. It is lighter than air, its
density being 0.589 times that of air. It is easily liquefied due to the strong hydrogen
bonding between molecules; the liquid boils at −33.1 °C (−27.58 °F), and freezes to white
crystals[22] at −77.7 °C (−107.86 °F).
Solid
The crystal symmetry is cubic, Pearson symbol cP16, space group P213 No.198,
lattice constant 0.5125 nm.[26]
Liquid
Liquid ammonia possesses strong ionising powers reflecting its high ε of 22. Liquid
ammonia has a very high standard enthalpy change of
vaporization (23.35 kJ/mol, cf. water 40.65 kJ/mol, methane
8.19 kJ/mol, phosphine 14.6 kJ/mol) and can therefore be used in laboratories in
uninsulated vessels without additional refrigeration. See liquid ammonia as a solvent.
Solvent properties
Ammonia readily dissolves in water. In an aqueous solution, it can be expelled by
boiling. The aqueous solution of ammonia is basic. The maximum concentration of
ammonia in water (a saturated solution) has a density of 0.880 g/cm3 and is often
known as '.880 ammonia'.
Combustion
Ammonia does not burn readily or sustain combustion, except under narrow fuel-to-
air mixtures of 15–25% air. When mixed with oxygen, it burns with a pale yellowish-
green flame. Ignition occurs when chlorine is passed into ammonia, forming nitrogen
and hydrogen chloride; if chlorine is present in excess, then the highly
explosive nitrogen trichloride (NCl3) is also formed.
Decomposition
At high temperature and in the presence of a suitable catalyst or in a pressurized
vessel with constant volume and high temperature (e.g. 1,100 °C (2,010 °F)),
ammonia is decomposed into its constituent elements.[27] Decomposition of ammonia is
a slightly endothermic process requiring 23 kJ/mol (5.5 kcal/mol) of ammonia, and
yields hydrogen and nitrogen gas. Ammonia can also be used as a source of hydrogen
for acid fuel cells if the unreacted ammonia can be
removed. Ruthenium and platinum catalysts were found to be the most active,
whereas supported Ni catalysts were less active.