Sulfur trioxide

Sulfur trioxide
	; Resonance structures
	; Space-filling model
Names
	Preferred IUPAC name Sulfur trioxide
	Systematic IUPAC name Sulfonylideneoxidane
	Other names Sulfuric anhydride, Sulfur(VI) oxide
Identifiers
CAS Number	7446-11-9 ;
3D model (JSmol)	monomer: Interactive image; γ-trimer: Interactive image; α/β polymer: Interactive image; (monohydrate): Interactive image;
ChEBI	CHEBI:29384 ;
ChemSpider	23080 ;
ECHA InfoCard	100.028.361
EC Number	231-197-3;
Gmelin Reference	1448
PubChem CID	24682; 22235242 ; (hemihydrate); (monohydrate): 23035042;
RTECS number	WT4830000;
UNII	HH2O7V4LYD ;
UN number	UN 1829
CompTox Dashboard (EPA)	DTXSID1029673 ;
	InChI InChI=1S/O3S/c1-4(2)3 Key: AKEJUJNQAAGONA-UHFFFAOYSA-N ; InChI=1/O3S/c1-4(2)3 Key: AKEJUJNQAAGONA-UHFFFAOYAX; (monohydrate): InChI=1S/O3S.H2O/c1-4(2)3;/h;1H2 Key: DEUOBQUHDSDIFY-UHFFFAOYSA-N;
	SMILES monomer: O=S(=O)=O; γ-trimer: O=S0(=O)OS(=O)(=O)OS(=O)(=O)O0; α/β polymer: OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)O; (monohydrate): O.O=S(=O)=O;
Properties
Chemical formula	SO3
Molar mass	80.066 g/mol
Appearance	Colorless to white crystalline solid which will fume in air. Colorless liquid and gas.
Odor	Varies. Vapor is pungent; like sulfur dioxide. Mist is odorless.
Density	1.92 g/cm3, liquid
Melting point	16.9 °C (62.4 °F; 290.0 K)
Boiling point	45 °C (113 °F; 318 K)
Solubility in water	Reacts to give sulfuric acid
Thermochemistry
Std molar; entropy (S⦵298)	256.77 JK−1mol−1
Std enthalpy of; formation (ΔfH⦵298)	−395.7 kJ/mol
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	Highly corrosive, extremely strong dehydrating agent
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H314, H335
Precautionary statements	P261, P280, P305+P351+P338, P310
NFPA 704 (fire diamond)	3 0 3 W; OX
Flash point	Non-flammable
	Lethal dose or concentration (LD, LC):
LC50 (median concentration)	rat, 4 hr 375 mg/m3[citation needed]
Safety data sheet (SDS)	ICSC 1202
Related compounds
Other cations	Selenium trioxide; Tellurium trioxide; Polonium trioxide
Related sulfur oxides	Sulfur monoxide; Sulfur dioxide
Related compounds	Sulfuric acid
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Sulfur trioxide (alternative spelling sulphur trioxide) is the chemical compound with the formula SO₃. It has been described as "unquestionably the most [economically] important sulfur oxide".^[1] It is prepared on an industrial scale as a precursor to sulfuric acid.

Sulfur trioxide exists in several forms: gaseous monomer, crystalline trimer, and solid polymer. Sulfur trioxide is a solid at just below room temperature with a relatively narrow liquid range. Gaseous SO₃ is the primary precursor to acid rain.^[6]

^ ^a ^b Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 703–704. ISBN 978-0-08-037941-8.
^ "SULFUR TRIOXIDE CAMEO Chemicals NOAA". Cameochemicals.noaa.gov.
^ ^a ^b Lerner, L. (2011). Small-Scale Synthesis of Laboratory Reagents with Reaction Modeling. CRC Press. p. 10. ISBN 9781439813133. LCCN 2010038460.
^ "Substance:Sulfur trioxide - Learn Chemistry Wiki". Rsc.org.
^ "Sulfur trioxide 227692" (PDF). SO3. Archived from the original on 2020-09-01. Retrieved 1 September 2020.
^ Thomas Loerting; Klaus R. Liedl (2000). "Toward elimination of descrepancies between theory and experiment: The rate constant of the atmospheric conversion of SO₃ to H₂SO₄". Proceedings of the National Academy of Sciences of the United States of America. 97 (16): 8874–8878. Bibcode:2000PNAS...97.8874L. doi:10.1073/pnas.97.16.8874. PMC 16788. PMID 10922048.

[G&E-1] Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 703–704. ISBN 978-0-08-037941-8.

[2] "SULFUR TRIOXIDE CAMEO Chemicals NOAA". Cameochemicals.noaa.gov.

[Lerner-3] Lerner, L. (2011). Small-Scale Synthesis of Laboratory Reagents with Reaction Modeling. CRC Press. p. 10. ISBN 9781439813133. LCCN 2010038460.

[4] "Substance:Sulfur trioxide - Learn Chemistry Wiki". Rsc.org.

[5] "Sulfur trioxide 227692" (PDF). SO3. Archived from the original on 2020-09-01. Retrieved 1 September 2020.

[6] Thomas Loerting; Klaus R. Liedl (2000). "Toward elimination of descrepancies between theory and experiment: The rate constant of the atmospheric conversion of SO₃ to H₂SO₄". Proceedings of the National Academy of Sciences of the United States of America. 97 (16): 8874–8878. Bibcode:2000PNAS...97.8874L. doi:10.1073/pnas.97.16.8874. PMC 16788. PMID 10922048.

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Names
Resonance structures
Space-filling model^[1]
Preferred IUPAC name Sulfur trioxide
Systematic IUPAC name Sulfonylideneoxidane
Other names Sulfuric anhydride, Sulfur(VI) oxide
Identifiers
CAS Number	7446-11-9^Y
3D model (JSmol)	monomer: Interactive image γ-trimer: Interactive image α/β polymer: Interactive image (monohydrate): Interactive image
ChEBI	CHEBI:29384^Y
ChemSpider	23080^Y
ECHA InfoCard	100.028.361
EC Number	231-197-3
Gmelin Reference	1448
PubChem CID	24682 22235242 (hemihydrate) (monohydrate): 23035042
RTECS number	WT4830000
UNII	HH2O7V4LYD^N
UN number	UN 1829
CompTox Dashboard (EPA)	DTXSID1029673
InChI InChI=1S/O3S/c1-4(2)3^Y Key: AKEJUJNQAAGONA-UHFFFAOYSA-N^Y InChI=1/O3S/c1-4(2)3 Key: AKEJUJNQAAGONA-UHFFFAOYAX (monohydrate): InChI=1S/O3S.H2O/c1-4(2)3;/h;1H2 Key: DEUOBQUHDSDIFY-UHFFFAOYSA-N
SMILES monomer: O=S(=O)=O γ-trimer: O=S0(=O)OS(=O)(=O)OS(=O)(=O)O0 α/β polymer: OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)OS(=O)(=O)O (monohydrate): O.O=S(=O)=O
Properties
Chemical formula	SO₃
Molar mass	80.066 g/mol
Appearance	Colorless to white crystalline solid which will fume in air.^[2] Colorless liquid and gas.^[3]
Odor	Varies. Vapor is pungent; like sulfur dioxide.^[4] Mist is odorless.^[3]
Density	1.92 g/cm³, liquid
Melting point	16.9 °C (62.4 °F; 290.0 K)
Boiling point	45 °C (113 °F; 318 K)
Solubility in water	Reacts to give sulfuric acid
Thermochemistry
Std molar entropy (S^⦵₂₉₈)	256.77 JK⁻¹mol⁻¹
Std enthalpy of formation (Δ_fH^⦵₂₉₈)	−395.7 kJ/mol
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Highly corrosive, extremely strong dehydrating agent
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H314, H335
Precautionary statements	P261, P280, P305+P351+P338, P310^[5]
NFPA 704 (fire diamond)	3 0 3 W OX
Flash point	Non-flammable
Lethal dose or concentration (LD, LC):
LC₅₀ (median concentration)	rat, 4 hr 375 mg/m³^{[citation needed]}
Safety data sheet (SDS)	ICSC 1202
Related compounds
Other cations	Selenium trioxide Tellurium trioxide Polonium trioxide
Related sulfur oxides	Sulfur monoxide Sulfur dioxide
Related compounds	Sulfuric acid
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