Talk:Dichlorine heptoxide

CAS number

According to [1] (retrieved 2009-05-27), the CAS number for chlorine heptoxide (Cl
₂O
₇) is 10294-48-1, but this article currently lists it as 12015-53-1. Which one is the right one??—Tetracube (talk) 16:55, 27 May 2009 (UTC)

Found another reference for 10294-48-1: Yaws, Carl L. (1998). Chemical properties handbook: physical, thermodynamic, environmental, transport, safety, and health related properties for organic and inorganic chemicals. McGraw-Hill Professional. p. 667. ISBN 0070734011. I'll go ahead and fix the number.—Tetracube (talk) 17:19, 27 May 2009 (UTC)

rocket fuel?

why doesn't somebody use this as a rocket fuel? It's got almost twice the energy density of lox. — Preceding unsigned comment added by 2600:8801:0:1530:B479:48D0:6B69:DDE9 (talk) 13:41, 9 February 2017 (UTC)

In chapter 6 of "Ignition! An Informal History of Liquid Rocket Propellants" by John Drury Clark, on pages 78 and 79, it says: "While the preliminary work with CTF was going on, and people were trying to come up with a good fuel for it, they were also looking very hard at the oxides of chlorine and their derivatives. Cl₂O₇, with an endothermic heat of formation of +63.4 kcal/mole, was one of the most powerful liquid oxidizers known in the early 50's, and preliminary calculations showed that it should give a remarkably high performance with any number of fuels. It had, however, one slight drawback — it would detonate violently at the slightest provocation or none at all. From first to last, at least five laboratories tried to domesticate it, with no success at all. The approach was to hunt for additives which would desensitize or stabilize it — Olin Mathieson, alone, tried some seventy — and was a dismal failure." DubleH (talk) 12:40, 3 March 2021 (UTC)

How is it endergonic?

Because fordecomposition, it says ΔH = 135 kJ/mol, which indicates exergonicity. Alfa-ketosav (talk) 20:55, 17 November 2018 (UTC)

Someone seems to have corrected it to -135 kJ/mol (presumably that's correct), but I want to point out that having a positive ΔH of decomposition makes forming the compound exo*thermic*, not necessarily exer*gonic*. Whether it is depends on the entropy of the products and reactants. Cl₂O₇ almost certainly has less specific entropy than the Cl₂ + 3.5O₂ form, since one is a liquid and the other is a gas, thus decomposition could still be exergonic/spontaneous (making the compound "endergonic"), even if the decomposition process were endothermic (so that making the compound from the elements would be exothermic.) Endothermic exergonic decomposition processes (such as of "exothermic" "endergonic" compounds to their component elements) are actually very common and are how many compounds break down when you increase the temperature, for example.DubleH (talk) 21:49, 29 November 2020 (UTC)

Phosphorous Pentoxide vs Octoxide

Someone seems to have recently changed "phosphorus pentoxide" to "phosphorus octoxide". The latter could refer to P₄O₈, but the equation below clearly uses phosphorus pentoxide (P₄O₁₀), which is a more common drying agent. The source in inaccessible to me, though, so I don't want to change it back and cite the same source, since the change might have been to make the article match what the source actually described.DubleH (talk) 21:36, 29 November 2020 (UTC)