Talk:Sulfur trioxide

Picture of Lewis Structure
Looking at the discussion below, shouldn't the picture be changed to one that shows two single bonds and a double bond? Theislikerice (talk) 14:14, 2 November 2012 (UTC)

Bonding
What is the bond structure of SO3?
 * Not a simple question! The physical fact is that SO3 is trigonal planar with three equivalent sulfur–oxygen bonds. It is usual to describe these bond as double bonds, thus breaching the octet rule. For a more complete description of the theoretical controversy surrounding such breaches of the octet rule, see hypervalent molecule. I would add that IMHO sulfur–oxygen &pi;-bonds have a relatively minor contribution to the overall bonding scheme. Physchim62 08:38, 24 May 2005 (UTC)

Erm... Actually, it's a very simple question. The octet rule only really applies to the 2nd period. Elements in period 3 or lower have access to the d-subshell (the transition metal block). As a result, they have a maximum of 18 outer shell electrons. Hence, for transition metals and lower main group chemistry, the 18 electron rule can be used instead.

So: Sulphur Trioxide... 3 Oxygen atoms which can only be at an oxidation state of -2 (because oxygen doesn't like anything other than -2 or 0), so subtract that leaves 12 outer shell electrons around the sulphur nucleus. Thus sulphur is present in it's +4 oxidation state. All oxidation states comply and the total of 18 electrons is maintained.

Oh, anf FYI, the molecule exhibits sp<sup3 d hybridisation, unless I'm mistaken. I'm a little hazy on the exact bonding structure, however... It's been a couple of years. --Xanthine 12:14, 25 January 2006 (UTC)
 * I've never seen the 18 electron rule applied to main group compounds: it is widely breached for transition metal compounds in any case. And the sulfur in sulfur trioxide is in oxidation state +6... Physchim62 (talk) 14:03, 25 January 2006 (UTC)
 * @Xanthine: It's sp2 hybridization, hence the trigonal planar shape. --Spoon! 08:01, 31 August 2006 (UTC)

The sulfur in SO3 does not need to breach the octet rule. The sulfur trioxide molecule exhibits resonance, with one double and two single bonds to the oxygens. The molecule is trigonal planar, but the bonds are not double bonds. Instead, the molecule exhibits one delocalized pi bond (the molecule has resonant structures). Roznerjs (talk) 03:14, 25 April 2008 (UTC)

Nomenclature
(Transferred from main article and edited for HTML. Physchim62 20:12, 16 September 2005 (UTC))

The nomenclature in the synthesis of SO3 is not correct. Sodium bisulfate = sodium pyrosulfate = NaHSO4. On the contrary, Sodium PERsulfate is something quite different: Na2S2O8. This is probably what is synthesised. 131.174.15.229 10:09, 12 September 2005 (UTC)


 * Sodium bisulphate is NaHSO4, sodium pyrosulphate is Na2S2O7. Historically, this has often been written Na2SO4.SO3 particulally in patents.  This does give off SO3 when strongly heated.


 * To make the Persulphate, a strong oxidising agent, you need another oxidising agent, typically hydrogen peroxide or by electrolysis, though this is not a good method to make sulphur trioxide. Ambix 20:24, 14 December 2005 (UTC)

Cookbook for sulfur trioxide?
What's up with the cookbook recipe-like section on how to make sulfur trioxide? It's pretty funny, the way it's written, to read, though. ;) Bayerischermann 23:53, 2 October 2005 (UTC)
 * There already is a repice for making it from the NaHSO4.
 * I'd like to clarify, that only the sodium bisulfate is suitable for sulfur trioxide preparation, ammonium and potassium won't work (break into O2 and SO2).
 * Here's a reference http://doc.utwente.nl/68103/1/Vries69thermal.pdf

Sigma Aldrich
The link "Sigma Aldrich" does not guide me to a specific page about "Sulfur trioxide". It seems, that this is a spam link.

That was not trying to be a spam link, the MSDS there is a good source of information but I am not sure that it is citable. The main thing is that the NFPA health hazard is a 4 not a 3. If you go to: http://www.sigmaaldrich.com/catalog/ProductDetail.do?lang=en&N4=425478|ALDRICH&N5=SEARCH_CONCAT_PNO|BRAND_KEY&F=SPEC then download the MSDS, the NFPA rating can be seen. ShreadedWheat (talk) 18:19, 2 August 2011 (UTC)ShreadedWheat

More about "chemical suppliers": http://en.wikipedia.org/wiki/User_talk:213.188.227.119

Best regards

Crystal Structure
I believe that the gamma form is hexagonal, but I can't find a reference to verify this. Anybody who can verify this is invited to add the fact to the Crystal Structure paragraph. Karlhahn 17:37 13 August 2006 (UTC)

Structure of Solid
Smokefoot has eliminated the conditions under which the mixed alpha-beta-gamma forms arise. The section as it now stands begs the question of how to get the beta form. Karlhahn 19:15, 21 August 2006 (UTC)
 * I will be re-revising this rapidly changing but important article. I left a note on your Talk page.  --Smokefoot 22:26, 21 August 2006 (UTC)

Reversion of H2SO4 to SO3 and Water
The text currently contains the sentence, "Only upon heating to ~340 °C does sulfuric acid revert to sulfur trioxide and water." This suggests that you can separate H2SO4 into SO3 and water simply by heating it. In reality you end up with a mixture of two gases (actually three gases because thermodynamics requires that some H2SO4 remain no matter how hot you get it) and like any gas mixture, it does not magically separate. So perhaps a qualifier to the sentence is in order -- something like, "although this is not a feasible means of separating H2SO4 into SO3 and water." Karlhahn 01:25, 22 August 2006 (UTC)
 * Yeah, I wrote or re-re-revised the offending bit. You go ahead and edit away. You do it your way. The main problem is specifying the temperature, implying that magically the equilibrium jumps to 100% conversion. Nice catch. --Smokefoot 01:39, 22 August 2006 (UTC)

Stub
Is this page still classified as a stub --Dinna89 12:10, 15 August 2006 (UTC)
 * No, its long enough to be a "start", but still needs some cleanup. Physchim62 (talk) 17:06, 17 August 2006 (UTC)

3-D Bonding Structure
This image should be added to the information box, I just have no idea how to do it. (http://commons.wikimedia.org/wiki/Image:Sulfur-trioxide-3D-vdW.png) —Preceding unsigned comment added by 66.130.16.181 (talk) 22:25, 29 November 2007 (UTC)

Infobox
I'm concerned about several things in the infobox. The density of the gas would be nice in there as its melting point is above room temperature. (The vapor is 2.76 time denser than air see the MSDS in link in the SigmaAldrich section.)

Where it says hydrolyzes to form sulfuric acid, where it actually takes up a water molecule to form sulfuric acid. Hydration would be more appropriate.

ShreadedWheat (talk) 18:43, 2 August 2011 (UTC)

Also the link listed as 3162-58-1 goes to a page that says that number doesn't exist. --81.149.74.231 (talk) 11:16, 24 May 2012 (UTC)

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Contradictory/confusing information about the structure of the SO3 molecule
At the top of the Sulfur trioxide properties table, there is an image of the SO3 molecule shown with three double bonds, implicating a bond order of 2. But suddenly, in the "Molecular structure and bonding" section, it says that the Lewis structure consists of an S=O double bond and two S–O dative bonds, implicating a bond order of 1.3333333333... The two structures contradict to each other. Or... are they? Why not two S=O double bonds and one S–O dative bond? Bernardirfan (talk) 18:13, 6 July 2020 (UTC)


 * I think that this is now addressed. KeeYou Flib (talk) 22:55, 11 February 2022 (UTC)

"Sulfan" listed at Redirects for discussion
A discussion is taking place to address the redirect Sulfan. The discussion will occur at Redirects for discussion/Log/2021 July 19 until a consensus is reached, and readers of this page are welcome to contribute to the discussion. Leyo 08:06, 19 July 2021 (UTC)