Sulfur dioxide

Sulfur dioxide

Chembox new
Name = Sulphur dioxide
ImageFileL1 = Sulfur-dioxide-2D.svg
ImageSizeL1 = 120
ImageFileR1 = Sulfur-dioxide-3D-vdW.png OtherNames = sulfur(IV) oxide; sulfurous anhydride
Section1 = Chembox Identifiers
CASNo = CASRN|7|4|4|6|0|9|5
ChemSpiderID = 1087
RTECS = WS4550000
Section2 = Chembox Properties
Formula = SO2
MolarMass = 64.07 g mol−1
Appearance = colourless gas
Density = 2.551 g/L, gas
1.354 g/cm³ at -30°C
1.434 g/cm³ at 0°C
1.25 g/mL at 25°C
Solubility = 9.4 g/100 mL (25 °C)
MeltingPt = −72.4 °C (200.75 K)
BoilingPt = −10 °C (263 K)
VaporPressure = –10°C : 1.013 bar
20°C : 3.3 bar
40°C : 4.4 bar
pKa = 1.81
Section3 = Chembox Structure
MolShape = Bent 120° [ [http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch8/table.php Table of Geometries based on VSEPR ] ]
Dipole = 1.63 D
Section7 = Chembox Hazards
FlashPt = non-flammable
EUClass = Toxic
RPhrases = R23 R34
SPhrases = S1/2 S9 S26 S36/37/39 S45LC503000 ppm/30 min mouse inhalation
NFPA-H = 3
Section8 = Chembox Related
OtherCpds = Sulfur trioxide; sulfuric acid

Sulfur dioxide (also sulphur dioxide) is the chemical compound with the formula SO2. SO2 is produced by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide. Further oxidation of SO2, usually in the presence of a catalyst such as NO2, forms H2SO4, and thus acid rain. [Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.] This is one of the causes for concern over the environmental impact of the use of these fuels as power sources.

Preparation

Sulfur dioxide can be prepared by burning sulfur::S8 + 8 O2 → 8 SO2The combustion of hydrogen sulfide and organosulfur compounds proceeds similarly.:2 H2S(g) + 3 O2(g) → 2 H2O(g) + 2 SO2(g)

The roasting of sulfide ores such as iron pyrites, sphalerite (zinc blende) and cinnabar (mercury sulfide) also releases SO2::4 FeS2(s) + 11 O2(g) → 2 Fe2O3(s) + 8 SO2(g):2 ZnS(s) + 3 O2(g) → 2 ZnO(s) + 2 SO2(g):HgS(s) + O2(g) → Hg(g) + SO2(g)

Sulfur dioxide is a by-product in the manufacture of calcium silicate cement: CaSO4 is heated with coke and sand in this process::2 CaSO4(s) + 2SiO2(s) + C(s) → 2 CaSiO3(s) + 2 SO2(g) + CO2(g)

Action of hot sulfuric acid on copper turnings produces sulfur dioxide.:Cu(s) + 2H2SO4(aq) → CuSO4(aq) + SO2(g) + 2H2O(l)

tructure and bonding

SO2 is a bent molecule with C2v symmetry point group. In terms of electron-counting formalisms, the sulfur atom has an oxidation state of +4, a formal charge of 0, and is surrounded by 5 electron pairs and can be described as a hypervalent molecule. From the perspective of molecular orbital theory, most of these valence electrons are engaged in S-O bonding.


* The values are tabulated for 101.3 kPa partial pressure of SO2. Solubility of gas in a liquid depends on the gas partial pressure according to Henry's law.
* The solubility is given for "pure water", i.e., water that contains only SO2 in the amount at equilibrium with the gas phase. This "pure water" is going to be acidic. The solubility of SO2 in neutral (or alkaline) water is generally going to be higher because of the pH-dependent speciation of SO2 in the solution with the production of bisulfite and some sulfite ions.

Threats to Health

Sulfur dioxide acts as an acid. Inhalation results in labored breathing, coughing, and/or a sore throat and may cause permanent pulmonary damage. When mixed with water and contacted by skin, frostbite may occur. When it makes contact with eyes, redness and pain will occur. [ [http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc00/icsc0074.htm SULPHUR DIOXIDE] , International Labour Organization.]

References

ee also

* Sulfur trioxide
* Sulfur-iodine cycle
* National Ambient Air Quality Standards
* Homer City Generating Station
*

External links

* [http://www.epa.gov/air/airtrends/sulfur.html United States Environmental Protection Agency Sulfur Dioxide page]
* [http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc00/icsc0074.htm International Chemical Safety Card 0074]
* [http://www-cie.iarc.fr/htdocs/monographs/vol54/02-sulfur-dioxide.htm IARC Monograph "Sulfur Dioxide and some Sulfites, Bisulfites and Metabisulfites"]
* [http://www.cdc.gov/niosh/npg/npgd0575.html NIOSH Pocket Guide to Chemical Hazards]
* [http://www.fedupwithfoodadditives.info/factsheets/Factsulphites.htm Food Intolerance Network] - Sulfite factsheet
* [http://www.chm.bris.ac.uk/motm/so2/so2h.htm Sulfur Dioxide, Molecule of the Month]


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Look at other dictionaries:

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  • sulfur dioxide — n. a heavy, colorless, suffocating gas, SO2, easily liquefied and used as a bleach, disinfectant, preservative, etc …   English World dictionary

  • sulfur dioxide — Chem. a colorless, nonflammable, water soluble, suffocating gas, SO2, formed when sulfur burns: used chiefly in the manufacture of chemicals such as sulfuric acid, in preserving fruits and vegetables, and in bleaching, disinfecting, and… …   Universalium

  • sulfur dioxide — sieros(IV) oksidas statusas T sritis chemija formulė SO₂ atitikmenys: angl. sulfur dioxide; sulfur(IV) oxide rus. сернистый ангидрид; сернистый газ; серы двуокись; серы диоксид; серы(IV) оксид ryšiai: sinonimas – sieros dioksidas …   Chemijos terminų aiškinamasis žodynas

  • sulfur dioxide — sulfur di oxide the American spelling of ↑sulphur dioxide …   Dictionary of contemporary English

  • sulfur dioxide — noun a colorless toxic gas (SO2) that occurs in the gases from volcanoes; used in many manufacturing processes and present in industrial emissions; causes acid rain • Syn: ↑sulphur dioxide • Hypernyms: ↑dioxide, ↑gas, ↑pollutant * * * (US) (or… …   Useful english dictionary

  • sulfur dioxide — noun (U) the American spelling of sulphur dioxide …   Longman dictionary of contemporary English

  • sulfur dioxide — sul′fur diox′ide n. chem. a colorless, nonflammable, water soluble, suffocating gas, SO2, formed when sulfur burns: used chiefly in the manufacture of chemicals such as sulfuric acid, in preserving fruits and vegetables, and in bleaching,… …   From formal English to slang

  • sulfur dioxide — noun Date: 1869 a heavy pungent toxic gas SO2 that is easily condensed to a colorless liquid, is used especially in making sulfuric acid, in bleaching, as a preservative, and as a refrigerant, and is a major air pollutant especially in industrial …   New Collegiate Dictionary

  • sulfur dioxide — noun A toxic gas, of molecular formula SO that is found in the emissions of volcanos and those of burning coal or petroleum; dissolves in water to form sulfurous acid and, in the presence of oxygen, sulfuric acid, and is thus responsible for …   Wiktionary

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