Sulphur Dioxide
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| Names | |
|---|---|
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IUPAC name
Sulfur dioxide
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| Other names
Sulfurous anhydride
Sulfur(IV) oxide |
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| Identifiers | |
7446-09-5 
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| 3D model (Jmol) | Interactive image |
| 3535237 | |
| ChEBI |
CHEBI:18422
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| ChEMBL |
ChEMBL1235997 
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| ChemSpider |
1087
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| ECHA InfoCard | 100.028.359 |
| EC Number | 231-195-2 |
| E number | E220 (preservatives) |
| 1443 | |
| KEGG |
D05961
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| MeSH | Sulfur+dioxide |
| PubChem | 1119 |
| RTECS number | WS4550000 |
| UNII |
0UZA3422Q4
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| UN number | 1079, 2037 |
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| Properties | |
| SO 2 |
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| Molar mass | 64.066 g mol−1 |
| Appearance | Colorless gas |
| Odor | Pungent; similar to a just-struck match |
| Density | 2.6288 kg m−3 |
| Melting point | −72 °C; −98 °F; 201 K |
| Boiling point | −10 °C (14 °F; 263 K) |
| 94 g/L | |
| Vapor pressure | 237.2 kPa |
| Acidity (pKa) | 1.81 |
| Basicity (pKb) | 12.19 |
| −18.2·10−6 cm3/mol | |
| Viscosity | 0.403 cP (at 0 °C) |
| Structure | |
| C2v | |
| Digonal | |
| Dihedral | |
| 1.62 D | |
| Thermochemistry | |
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Std molar
entropy (S |
248.223 J K−1 mol−1 |
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Std enthalpy of
formation (ΔfH |
−296.81 kJ mol−1 |
| Hazards | |
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EU classification (DSD)
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 T |
| R-phrases | R23, R34, R50 |
| S-phrases | (S1/2), S9, S26, S36/37/39, S45 |
| NFPA 704 | |
| Lethal dose or concentration (LD, LC): | |
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LC50 (median concentration)
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3000 ppm (mouse, 30 min) 2520 ppm (rat, 1 hr) |
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LCLo (lowest published)
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993 ppm (rat, 20 min) 611 ppm (rat, 5 hr) 764 ppm (mouse, 20 min) 1000 ppm (human, 10 min) 3000 ppm (human, 5 min) |
| US health exposure limits (NIOSH): | |
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PEL (Permissible)
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TWA 5 ppm (13 mg/m3) |
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REL (Recommended)
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TWA 2 ppm (5 mg/m3) ST 5 ppm (13 mg/m3) |
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IDLH (Immediate danger)
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100 ppm |
| Related compounds | |
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Sulfur monoxide Sulfur trioxide |
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Related compounds
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Ozone |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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 (what is ?) |
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| Infobox references | |
Selenium dioxide
Sulfurous acid
Tellurium dioxide
Sulfur dioxide (also sulphur dioxide) is the chemical compound with the formula SO
2. At standard atmosphere, it is a toxic gas with a pungent, irritating smell. The triple point is 197.69 K and 1.67 kPa. It is released naturally by volcanic activity.
Sulfur dioxide was used by the Romans in winemaking when they discovered that burning sulfur candles inside empty wine vessels kept them fresh and free from vinegar smell.
SO2 is a bent molecule with C2vsymmetry point group. A valence bond theory approach considering just s and p orbitals would describe the bonding in terms of resonance between two resonance structures.
The sulfur–oxygen bond has a bond order of 1.5. There is support for this simple approach that does not invoke d orbital participation. In terms of electron-counting formalism, the sulfur atom has an oxidation state of +4 and a formal charge of +1.
It is found on Earth and exists in very small concentrations and in the atmosphere at about 1 ppm.
On other planets, it can be found in various concentrations, the most significant being the atmosphere of Venus, where it is the third-most significant atmospheric gas at 150 ppm. There, it condenses to form clouds, and is a key component of chemical reactions in the planet's atmosphere and contributes to global warming. It has been implicated as a key agent in the warming of early Mars, with estimates of concentrations in the lower atmosphere as high as 100 ppm, though it only exists in trace amounts. On both Venus and Mars, its primary source, like on Earth, is thought to be volcanic. The atmosphere of Io is 90% sulfur dioxide and trace amounts are thought to also exist in the atmosphere of Jupiter.
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Wikipedia