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Hydrogen sulfide

chemical compound

Hydrogen sulfide (British English: hydrogen sulphide) is the chemical compound with the formula H
2
S
, is a colorless, toxic, flammable gas that is responsible for the foul smell of rotten eggs and flatulence. It often results when bacteria break down organic matter in the absence of oxygen. This happens in swamps, and sewers (alongside the process of anaerobic digestion). It also occurs in volcanic gases, natural gas and some well waters. This is the smell that people often think to be that of sulfur. But sulfur itself does not smell.

Hydrogen sulfide
Ball-and-stick model of hydrogen sulfide
Spacefill model of hydrogen sulfide
Names
Systematic IUPAC name
Hydrogen sulfide[1]
Other names
  • Dihydrogen monosulfide
  • Dihydrogen sulfide
  • Sewer gas
  • Sulfane
  • Sulfurated hydrogen
  • Sulfureted hydrogen
  • Sulfuretted hydrogen
  • Sulfur hydride
  • Hydrosulfuric acid
  • Hydrothionic acid
  • Thiohydroxic acid
  • Sulfhydric acid
Identifiers
3D model (JSmol)
3DMet {{{value}}}
Beilstein Reference 3535004
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.029.070
EC Number 231-977-3
Gmelin Reference 303
KEGG
MeSH {{{value}}}
PubChem {{{value}}}
RTECS number MX1225000
UNII
UN number 1053
SMILES {{{value}}}
Properties
H2S
Molar mass 34.08 g·mol−1
Appearance Colorless gas
Odor Rotten eggs
Density 1.363 g dm−3
Melting point −82 °C (−116 °F; 191 K)
Boiling point −60 °C (−76 °F; 213 K)
4 g dm−3 (at 20 °C)
Vapor pressure 1740 kPa (at 21 °C)
Acidity (pKa) 7.0[2][3]
Conjugate acid Sulfonium
Conjugate base Bisulfide
−25.5·10−6 cm3/mol
1.000644 (0 °C)[4]
Structure
C2v
Bent
0.97 D
Thermochemistry
Std enthalpy of
formation
ΔfHo298
−21 kJ mol−1[5]
Standard molar
entropy
So298
206 J mol−1 K−1[5]
Specific heat capacity, C 1.003 J K−1 g−1
Hazards
EU classification Flammable F+ Very Toxic T+ Dangerous for the Environment (Nature) N
Main hazards Flammable and highly toxic
NFPA 704

NFPA 704.svg

4
4
0
 
R-phrases R12, R26, R50
S-phrases (S1/2), S9, S16, S36, S38, S45, S61
Explosive limits 4.3–46%
U.S. Permissible
exposure limit (PEL)
C 20 ppm; 50 ppm [10-minute maximum peak]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Hydrogen sulfide is also known as sulfane, sulfur hydride, sour gas, sulfurated hydrogen, hydrosulfuric acid, sewer gas and stink damp. IUPAC accepts the names "hydrogen sulfide" and "sulfane". When people speak of more complicated compounds they always use the term "sulfane".

OccurrenceEdit

 
Deposit of sulfur on a rock, caused by volcanic gases containing hydrogen sulfide

Small amounts of hydrogen sulfide can be found in crude petroleum. Sour natural gas can contain up to 28%. But, sour natural gas must be cleaned before it can enter a long distance pipeline. Pipelines limit hydrogen sulfide to 3 grains per thousand cubic feet of natural gas.[6] Volcanoes and hot springs give off some H2S, where it probably is made by the hydrolysis of sulfide minerals, i.e. MS + H2O to give MO + H2S.

Normal average concentration in clean air is about 0.0001-0.0002 ppm.

SafetyEdit

Hydrogen sulfide is a highly toxic and flammable gas. Because it is heavier than air it tends to accumulate at the bottom of poorly ventilated spaces.

ToxicityEdit

Hydrogen sulfide is considered a broad-spectrum poison, meaning that it can poison several different systems in the body, although the nervous system is most affected. The toxicity of H2S is comparable with that of hydrogen cyanide.

ReferencesEdit

  1. "Hydrogen Sulfide - PubChem Public Chemical Database". The PubChem Project. USA: National Center for Biotechnology Information.
  2. Perrin, D.D. (1982). Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution (2nd ed.). Oxford: Pergamon Press.
  3. Bruckenstein, S.; Kolthoff, I.M., in Kolthoff, I.M.; Elving, P.J. Treatise on Analytical Chemistry, Vol. 1, pt. 1; Wiley, NY, 1959, pp. 432–433.
  4. Patnaik, Pradyot (2002). Handbook of Inorganic Chemicals. McGraw-Hill. ISBN 0-07-049439-8.
  5. 5.0 5.1 Zumdahl, Steven S. (2009). Chemical Principles (6th ed.). Houghton Mifflin Company. p. A23. ISBN 0-618-94690-X.
  6. "Southern Natural Gas Company Tariff, General Terms and Conditions Section 3.1(b)". Retrieved October 18, 2011.
  • "Hydrogen Sulfide", Committee on Medical and Biological Effects of Environmental Pollutants, University Park Press, 1979, Baltimore. ISBN 0-8391-0127-9

Other websitesEdit