Sulfur dioxide

Sulfur dioxide (also sulphur dioxide) is the chemical compound with the formula SO₂. It is a gas. It smells like burnt matches or rotten eggs. It can also cause suffocation. Sulfur dioxide is produced by volcanoes and in various industrial processes. It is also used to protect wine from oxygen and bacteria. It can be produced by burning sulfur. It dissolves in water to produce sulfurous acid. It can be oxidized to trioxide, which is dissolved in sulfuric acid to make more sulfuric acid. It is used to make sulfites.

Sulfur dioxide

Names
IUPAC name Sulfur dioxide
Other names Sulfurous anhydride Sulfur(IV) oxide
Identifiers
CAS Number	7446-09-5 Y
3D model (JSmol)	Interactive image
Beilstein Reference	3535237
ChEBI	CHEBI:18422 Y
ChEMBL	ChEMBL1235997 N
ChemSpider	1087 Y
ECHA InfoCard	100.028.359
EC Number	231-195-2
E number	E220 (preservatives)
Gmelin Reference	1443
KEGG	D05961 Y
MeSH	Sulfur+dioxide
PubChem CID	1119
RTECS number	WS4550000
UNII	0UZA3422Q4 Y
UN number	1079, 2037
CompTox Dashboard (EPA)	DTXSID6029672
SMILES O=S=O
Properties
Chemical formula	SO 2
Molar mass	64.066 g mol−1
Appearance	Colorless gas
Odor	Pungent; similar to a just-struck match[1]
Density	2.6288 kg m−3
Melting point	−72 °C; −98 °F; 201 K
Boiling point	−10 °C (14 °F; 263 K)
Solubility in water	94 g/L[2] forms sulfurous acid
Vapor pressure	237.2 kPa
Acidity (pKa)	1.81
Basicity (pKb)	12.19
Magnetic susceptibility (χ)	−18.2·10−6 cm3/mol
Viscosity	0.403 cP (at 0 °C)
Structure
Point group	C2v
Coordination geometry	Digonal
Molecular shape	Dihedral
Dipole moment	1.62 D
Thermochemistry
Std enthalpy of formation ΔfHo298	−296.81 kJ mol−1
Standard molar entropy So298	248.223 J K−1 mol−1
Hazards
NFPA 704	0 3 0
U.S. Permissible exposure limit (PEL)	TWA 5 ppm (13 mg/m3)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references