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Encyclopedia > Sulfur dioxide
Sulfur dioxide
Other names sulfur(IV) oxide; sulfurous anhydride
Identifiers
CAS number [7446-09-5]
RTECS number WS4550000
Properties
Molecular formula SO2
Molar mass 64.054 g mol−1
Appearance colourless gas
Density 2.551 g/L, gas
Melting point

−72.4 °C (200.75 K) Image File history File links No higher resolution available. ... Image File history File links Download high-resolution version (1100x862, 141 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Sulfur dioxide User:Benjah-bmm27/Gallery User:Ben Mills/Gallery ... CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences, mixtures and alloys. ... RTECS, also known as Registry of Toxic Effects of Chemical Substances, is a database of toxicity information compiled from the open scientific literature that is available for charge. ... A chemical formula is an easy way of expressing information about the atoms that constitute a particular chemical compound. ... This article is about the chemical element. ... This article is about the chemical element and its most stable form, or dioxygen. ... Molar mass is the mass of one mole of a chemical element or chemical compound. ... For other uses, see Density (disambiguation). ... The melting point of a solid is the temperature range at which it changes state from solid to liquid. ...

Boiling point

−10 °C (263 K) Italic text This article is about the boiling point of liquids. ...

Solubility in water 9.4 g/100 mL (25 °C)
Acidity (pKa) 1.81
Structure
Molecular shape Bent 120°[1]
Dipole moment 1.63 D
Hazards
EU classification Toxic
NFPA 704
 
3
 
 
R-phrases R23 R34
S-phrases (S1/2) S9 S26 S36/37/39 S45
Flash point non-flammable
Related compounds
Related compounds Sulfur trioxide; sulfuric acid
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

Sulfur dioxide (also sulphur dioxide) is the chemical compound with the formula SO2. This important gas is the main product from the combustion of sulfur compounds and is of significant environmental concern. SO2 is often described as the "smell of burning sulfur" but is not responsible for the smell of rotten eggs. Solubility is a chemical property referring to the ability for a given substance, the solute, to dissolve in a solvent. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... An acid dissociation constant, denoted by Ka, is an equilibrium constant for the dissociation of a weak acid. ... Four sp3 orbitals. ... The Earths magnetic field, which is approximately a dipole. ... The debye (symbol: D) is a non-SI and non-CGS unit of electrical dipole moment. ... Council Directive 67/548/EEC of 27 June 1967 on the approximation of laws, regulations and administrative provisions relating to the classification, packaging and labelling of dangerous substances (as amended) is the main European Union law concerning chemical safety. ... NFPA 704 is a standard maintained by the U.S. National Fire Protection Association. ... Image File history File links NFPA_704. ... R-phrases are defined in Annex III of European Union Directive 67/548/EEC: Nature of special risks attributed to dangerous substances and preparations. ... S-phrases are defined in Annex IV of European Union Directive 67/548/EEC: Safety advice concerning dangerous substances and preparations. ... For other uses, see Flash point (disambiguation). ... “SO3” redirects here. ... Sulfuric acid, (also known as sulphuric acid) H2SO4, is a strong mineral acid. ... The plimsoll symbol as used in shipping In chemistry, the standard state of a material is its state at 1 bar (100 kilopascals exactly). ... Look up chemical compound in Wiktionary, the free dictionary. ... This article is about the chemical element. ... Hydrogen sulfide (hydrogen sulphide in British English) is the chemical compound with the formula H2S. This colorless, toxic and flammable gas is responsible for the foul odor of rotten eggs and flatulence. ...


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.[2] It can be easily liquefied in a standard home freezer. Cleveland Volcano in the Aleutian Islands of Alaska photographed from the International Space Station For other uses, see Volcano (disambiguation). ... Coal Example chemical structure of coal Coal is a fossil fuel formed in ecosystems where plant remains were saved by water and mud from oxidization and biodegradation. ... Petro redirects here. ... [1] R-phrases , S-phrases , , , , , Supplementary data page Structure and properties n, εr, etc. ... Sulfuric acid, (also known as sulphuric acid) H2SO4, is a strong mineral acid. ... The term acid rain is commonly used to mean the deposition of acidic components in rain, snow, fog, dew, or dry particles. ...

Contents

Preparation

Sulfur dioxide can be prepared by burning sulfur: This article is about the chemical element. ...

S8 + 8 O2 → 8 SO2

The combustion of hydrogen sulfide and organosulfur compounds proceeds similarly. Hydrogen sulfide (hydrogen sulphide in British English) is the chemical compound with the formula H2S. This colorless, toxic and flammable gas is responsible for the foul odor of rotten eggs and flatulence. ...

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: The mineral pyrite, or iron pyrite, is iron disulfide, FeS2. ... Sphalerite sample Another sphalerite sample The unit cell of sphalerite Sphalerite (ZnS) is a gay mineral that is the chief ore of zinc. ... Cinnabar, sometimes written cinnabarite, is a name applied to red mercury(II) sulfide (HgS), or native vermilion, the common ore of mercury. ...

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 cement: CaSiO3 and CaSO4 is heated with coke and sand in this process: General Name, symbol, number iron, Fe, 26 Chemical series transition metals Group, period, block 8, 4, d Appearance lustrous metallic with a grayish tinge Standard atomic weight 55. ... General Name, symbol, number zinc, Zn, 30 Chemical series transition metals Group, period, block 12, 4, d Appearance bluish pale gray Standard atomic weight 65. ... For other uses, see Cement (disambiguation). ... Calcium silicate, otherwise known as slag, has a low bulk density and high physical water absorption. ... Calcium sulphate is a common laboratory and industrial chemical. ... Coke Coke is a solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal. ...

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. Sulfuric acid, (also known as sulphuric acid) H2SO4, is a strong mineral acid. ... Various examples of swarf, including a block of compressed swarf Swarf (or turnings) is shavings and chippings of metal -- the debris or waste resulting from metalworking operations. ...

Cu(s) + 2H2SO4(aq) → CuSO4(aq) + SO2(g) + 2H2O(l)

Structure 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. Group theory is that branch of mathematics concerned with the study of groups. ... Electron counting is a formalism used for classifying compounds and for explaining or predicting electronic structure and bonding. ... In chemistry, the oxidation state is an indicator of the degree of oxidation of an atom in a chemical compound. ... In chemistry, a formal charge (FC) on an atom in a molecule is defined as: FC = number of valence electrons of the atom - number of Lone pair electrons on this atom - half the total number of electrons participating in covalent bonds with this atom. ... A lone pair is an electron pair without bonding or sharing with other atoms. ... A hypervalent molecule is a molecule that contains one or more typical elements (group 1, 2, 13-18) formally bearing more than eight electrons in their valence shells. ... In chemistry, molecular orbital theory (MO theory) is a method for determining molecular structure in which electrons are not assigned to individual bonds between atoms, but are treated as moving under the influence of the nuclei in the whole molecule. ...

three resonance structures of sulfur dioxide

The S-O bonds are shorter in SO2 (143.1 pm) than in sulfur monoxide, SO (148.1 pm), whereas the O-O bonds are longer in O3 (127.8 pm) than in dioxygen, O2 (120.7 pm). The mean bond energy is greater in SO2 (548 kJ mol−1) than in SO (524 kJ mol−1), whereas its is less in O3 (297 kJ mol−1) than in O2 (490 kJ mol−1). These pieces of evidence lead chemists to conclude that the S-O bonds in sulfur dioxide have a bond order of at least 2, unlike the O-O bonds in ozone, which have a bond order of 1.5[3] For other uses, see Resonance (disambiguation). ... In chemistry, Sulfur monoxide (formula: SO) is an unstable species that forms when monatomic oxygen O reacts with sulfur S2. ... Dioxygen, O2, is the most common form of the element oxygen in normal conditions. ... Bond order is the number of bonds between a pair of atoms. ... For other uses, see Ozone (disambiguation). ...


Reactions

Treatment of basic solutions with sulfur dioxide affords sulfite salts: Sulfites (also sulphite) are compounds that contain the sulfite ion SO32−. They are often used as preservatives in wines (to prevent spoilage and oxidation), dried fruits, and dried potato products. ...

SO2 + 2 NaOH → Na2SO3 + H2O

Featuring sulfur in the +4 oxidation state, sulfur dioxide is a reducing agent. It is oxidized by halogens such as chlorine to give the sulfuryl halides: A reducing agent (also called a reductant or reducer) is the element or a compound in a redox (reduction-oxidation) reaction (see electrochemistry) that reduces another species. ...

SO2 + Cl2SO2Cl2

However, on rare occasions, it can also act as an oxidising agent: in the Claus process, sulfur dioxide is reduced by hydrogen sulfide to give elemental sulfur: Sulfuryl chloride is SO2Cl2, a compound composed of sulfur, oxygen, and chlorine. ... An oxidizing agent is a substance that oxidizes another substance in electrochemistry or redox chemical reactions in general. ... This article needs to be cleaned up to conform to a higher standard of quality. ...

SO2 + 2 H2S → 3 S + 2 H2O

Sulfur dioxide can act as a metal binding ligand, typically where the transition metal is in oxidation state 0 or +1.[4] Up to 9 different bonding modes have been determined which include[4]: In chemistry, a ligand is an atom, ion, or molecule (see also: functional group) that generally donates one or more of its electrons through a coordinate covalent bond to, or shares its electrons through a covalent bond with, one or more central atoms or ions (these ligands act as a...

  • S donation -planar and pyramidal η1
  • O donation η1
  • π donation- side on η2
  • S bridging across two metal centres or two ends of a metal-metal bon
  • O-S bridging to two metal centres
  • bridging- one metal centre π donation- side on, the other metal center O donation
  • bridging over three metal centres

// η-bonding The Greek letter η (eta) is used to denote the number of atoms of a ligand that bind to a metal center. ... // η-bonding The Greek letter η (eta) is used to denote the number of atoms of a ligand that bind to a metal center. ... // η-bonding The Greek letter η (eta) is used to denote the number of atoms of a ligand that bind to a metal center. ...

Uses

As a preservative

Sulfur dioxide is sometimes used as a preservative for dried apricots and other dried fruits due to its antimicrobial properties, it is sometimes called E220 when used in this way. The preservative is used to maintain the appearance of the fruit and prevent rotting. Its presence can give fruit a distinctive chemical taste. This article does not cite any references or sources. ... Binomial name Prunus armeniaca L. For other uses, see Apricot (disambiguation). ... Dried fruit is fruit that has been dried, either naturally or through use of a machine, such as a dehydrator. ... An antimicrobial is a substance that kills or inhibits the growth of microbes such as bacteria. ... For other uses, see Decomposition (disambiguation). ... For the social and aesthetic aspects of taste, see taste (sociology). ...


In winemaking

Sulfur dioxide is a very important compound in winemaking, and is designated as parts per million in wine, E number: E220.[5] It is present even in so-called unsulphurated wine at concentrations of up to 10 milligrams per litre.[6] It serves as an antibiotic and antioxidant, protecting wine from spoilage by bacteria and oxidation. It also helps to keep volatile acidity at desirable levels. Sulfur dioxide is responsible for the words "contains sulfites" found on wine labels. Wines with SO2 concentrations below 10ppm do not require "contains sulfites" on the label by US and EU laws. The upper limit of SO2 allowed in wine is 350ppm in US, in the EU is 160 ppm for red wines and 210 ppm for white and rosé wines. In low concentrations SO2 is mostly undetectable in wine, but at over 50ppm, SO2 becomes evident in the nose and taste of wine. For the mathematical constant see: E (mathematical constant). ... For the song by The Feeling, see Rosé (song). ...


SO2 is also a very important element in winery sanitation. Wineries and equipment must be kept very clean, and because bleach cannot be used in a winery, a mixture of SO2, water, and citric acid is commonly used to clean hoses, tanks, and other equipment to keep it clean and free of bacteria.


As a reducing bleach

Sulfur dioxide is also a good reductant. In the presence of water, sulfur dioxide is able to decolorize substances. Specifically it is a useful reducing bleach for papers and delicate materials such as clothes. This bleaching effect normally does not last very long. Oxygen in the atmosphere reoxidizes the reduced dyes, restoring the color. A reducing agent (also called a reductant or reducer) is the element or a compound in a redox (reduction-oxidation) reaction (see electrochemistry) that reduces another species. ... This article is about the chemical whitener. ... For other uses, see Paper (disambiguation). ... This article is about the chemical element and its most stable form, or dioxygen. ...


Precursor to sulfuric acid

Sulfur dioxide is also used to make sulfuric acid, being converted to sulfur trioxide, and then to oleum, which is made into sulfuric acid. Sulfur dioxide for this purpose is made when sulfur combines with oxygen. The method of converting sulfur dioxide to sulfuric acid is called the contact process. “SO3” redirects here. ... Oleum refers to a solution of sulfur trioxide in sulfuric acid or sometimes more specifically to pyrosulfuric acid, disulfuric acid. ... Sulfuric acid, (also known as sulphuric acid) H2SO4, is a strong mineral acid. ... This article or section does not cite its references or sources. ...


Biochemical and biomedical roles

Sulfur dioxide is toxic in large amounts. It or its conjugate base bisulfite is produced biologically as an intermediate in both sulfate-reducing organisms and in sulfur oxidizing bacteria as well. Sulfur dioxide has no role in mammalian biology. Sulfur dioxide blocks nerve signals from the pulmonary stretch receptors (PSR's) and abolishes the Hering-Breuer inflation reflex. Pulmonary stretch receptors are mechanoreceptors found in the lungs. ... The Hering-Breuer reflex is a reflex triggered to prevent overinflation of the lungs. ...


As a refrigerant

Being easily condensed and with a high heat of evaporation, sulfur dioxide is a candidate material for refrigerants. Prior to the development of freons, sulfur dioxide was used as a refrigerant in home refrigerators. Tetrafluoroethane (a haloalkane) is a clear liquid which boils well below room temperature (as seen here) and can be extracted from common canned air canisters by simply inverting them during use. ... A refrigerant is a compound used in a heat cycle that undergoes a phase change from a gas to a liquid and back. ...


As a reagent and solvent

Sulfur dioxide is a versatile inert solvent that has been widely used for dissolving highly oxidizing salts. It is also used occasionally as a source of the sulfonyl group in organic synthesis. Treatment of aryldiazonium salts with sulfur dioxide affords the corresponding aryl sulfonyl chloride.[7] Organic synthesis is the construction of organic molecules via chemical processes. ... In chemistry, azo compounds generally have a molecular formula of the form R-N=N-R, in which R and R can be either aromatic or aliphatic. ...


Emissions

Sulfur dioxide emissions from the Halema`uma`u vent, glows at night
Sulfur dioxide emissions from the Halema`uma`u vent, glows at night

According to the U.S. EPA (as presented by the 2002 World Almanac or in chart form[8]), the following amount of sulfur dioxide was released in the U.S. per year, measured in thousands of short tons: EPA redirects here. ... For other uses, see United States (disambiguation) and US (disambiguation). ... The short ton is a unit of mass equal to 2000 lb (exactly 907. ...

*1999 18,867
*1998 19,491
*1997 19,363
*1996 18,859
*1990 23,678
*1980 25,905
*1970 31,161

Due largely to the US EPA’s Acid Rain Program, the U.S. has witnessed a 33 percent decrease in emissions between 1983 and 2002. This improvement resulted from flue gas desulfurization, a technology that enables SO2 to be chemically bound in power plants burning sulfur-containing coal or oil. In particular, calcium oxide (lime) reacts with sulfur dioxide to form calcium sulfite: For other uses of terms redirecting here, see US (disambiguation), USA (disambiguation), and United States (disambiguation) Motto In God We Trust(since 1956) (From Many, One; Latin, traditional) Anthem The Star-Spangled Banner Capital Washington, D.C. Largest city New York City National language English (de facto)1 Demonym American... The Acid Rain Program is a market-based initiative taken by the United States Environmental Protection Agency in an effort to reduce overall atmospheric levels of sulfur dioxide and nitrogen oxides, which cause acid rain [1]. The program is an implementation of emissions trading that primarily targets coal-burning power... Flue gas desulfurization is technology that employs a sorbent, usually lime or limestone, to remove sulfur dioxide(SO2) from the gases produced by burning fossil fuels. ... A power station (also power plant) is a facility for the generation of electric power. ... Coal Example chemical structure of coal Coal is a fossil fuel formed in ecosystems where plant remains were saved by water and mud from oxidization and biodegradation. ... Petro redirects here. ... Calcium oxide (CaO), commonly known as lime, quicklime or burnt lime, is a widely used chemical compound. ...

CaO + SO2 → CaSO3

Aerobic oxidation converts this CaSO3 into CaSO4, gypsum. Most gypsum sold in Europe comes from flue gas desulfurization. For other uses, see Gypsum (disambiguation). ...


New fuel additive catalysts, such as ferox, are being used in gasoline and diesel engines in order to lower the emission of sulfur oxide gases into the atmosphere. This is also done by forcing the sulfur into stable mineral salts and mixed mineral sulfates as opposed to sulfuric acid and sulfur oxides. Ferox is a fuel additive. ...


As of 2006, China is the world's largest sulfur dioxide polluter, with 2005 emissions estimated to be 25.49 million tons. This amount represents a 27% increase since 2000, and is roughly comparable with U.S. emissions in 1980[9].


Al-Mishraq, an Iraqi sulfur plant, was the site of a 2003 disaster resulting in the release of massive amounts of sulfur dioxide into the atmosphere. Al-Mishraq is a state run sulphur plant near Mosul, Iraq. ...


Temperature dependence of aqueous solubility

22 g/100ml (0 °C) 15 g/100ml (10 °C)
11 g/100ml (20 °C) 9.4 g/100 ml (25 °C)
8 g/100ml (30 °C) 6.5 g/100ml (40 °C)
5 g/100ml (50 °C) 4 g/100ml (60 °C)
3.5 g/100ml (70 °C) 3.4 g/100ml (80 °C)
3.5 g/100ml (90 °C) 3.7 g/100ml (100 °C)
  • 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 solublity 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 solublity 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.

In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. ... Solubility is a chemical property referring to the ability for a given substance, the solute, to dissolve in a solvent. ... In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. ... In chemistry, Henrys law is one of the gas laws, formulated by William Henry. ... For other uses, see PH (disambiguation). ... The bisulfite ion is the HSO3- ion. ... Sulfites (also sulphite) are compounds that contain the sulfite ion SO32−. They are often used as preservatives in wines (to prevent spoilage and oxidation), dried fruits, and dried potato products. ...

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.[10]


References

  1. ^ Table of Geometries based on VSEPR
  2. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
  3. ^ Greenwood, N. N.; Earnshaw, A. (1997). Chemistry of the Elements, 2nd Edition, Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.  p. 700
  4. ^ a b Greenwood, N. N.; Earnshaw, A. (1997). Chemistry of the Elements, 2nd Edition, Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4. 
  5. ^ Current EU approved additives and their E Numbers, The Food Standards Agency website.
  6. ^ Sulphites in wine, MoreThanOrganic.com.
  7. ^ R. V. Hoffman “m-Trifluoromethylbenzenesulfonyl chloride” Organic Syntheses, Collected Volume 7, p.508 (1990). http://www.orgsyn.org/orgsyn/pdfs/CV7P0508.pdf.
  8. ^ National Trends in Sulfur Dioxide Levels, United States Environmental Protection Agency.
  9. ^ China has its worst spell of acid rain, United Press International.
  10. ^ SULPHUR DIOXIDE, International Labour Organization.

EPA redirects here. ... Front of UPI Headquarters, Washington, D.C. “UPI” redirects here. ... The International Labour Organization (ILO) is a specialized agency of the United Nations that deals with labour issues. ...

See also

Wikimedia Commons has media related to:
sulfur dioxide

“SO3” redirects here. ... The sulfur-iodine cycle is a series of thermochemical processes used to produce hydrogen. ... The National Ambient Air Quality Standards (NAAQS) are standards established by the United States Environmental Protection Agency that apply for outdoor air throughout the country. ... Homer City Generating Station is a large coal fired power station at Minersville, Pennsylvania, USA. The Unit 3 of the Homer City Generating Station has a 371 metre tall chimney, which was built in 1977. ... Image File history File links Commons-logo. ...

External links


  Results from FactBites:
 
ATSDR - MMG: Sulfur Dioxide (4569 words)
Sulfur dioxide gas is released primarily from the combustion of fossil fuels (75% to 85% of the industrial sources), the smelting of sulfide ores, volcanic emissions, and several other natural sources.
Sulfur dioxide poisoning is not known to pose additional risk during the use of bronchial or cardiac sensitizing agents.
Sulfur dioxide is a severe irritant to the respiratory tract, eyes, mucous membranes, and skin.
sulfur dioxide - Encyclopedia.com (1235 words)
SO Sulfur dioxide is used in bleaching and in chemical manufacture and as a refrigerant and a food preservative, e.g., for fumigating fruit.
It may be produced by reaction of sulfur with oxygen, e.g., by burning sulfur in air, and it is often produced during the roasting of sulfide ores, e.g., in zinc smelting.
Sulfur dioxide is a dangerous air pollutant because of its corrosive properties; it irritates the eyes, nose, and lungs.
  More results at FactBites »

 
 

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