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woelen
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| Quote: | Originally posted by unionised
Phone NASA and tell them to cancel the next shuttle- perchlorates aren't fast oxidisers any more. |
Please read this thread more carefully  . We are talking here about redox
reactions in solution, in the cold, not about reactions of solids at high temperatures. So your comparison is not a valid one.
Perchlorates in the cold, dissolved in water, simply are NOT good oxidizing agents, evan at concentrations as high as 60%. Try it yourself!
And the list I compiled can be useful. E.g. a compound like Na2S2O8 can be very useful for analysis purposes, but for synthesis purposes it is less
useful (although not useless), simply because its reactions are so sluggish.
The list indeed must not be regarded as a scientificly founded list as the electrochemical series, it is more an indicative list. With some chemical
reactions, the positions of individual chemicals can be swapped, but the list gives a fairly good overall impression. That is all what I claim, not
more, not less.
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unionised
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I read this far
"I have made my own classification of oxidizer in speed of reaction. Speed of reaction is not the same as strength of oxidation. E.g. persulfate
is the strongest oxidizer I have, but also a rather sluggish one.
Mn2O7 (not aqueous, but very reactive)
"
and came to the conclusion that you were not talking about aqueous solutions any more so I'm not the one who moved the goalposts.
I'm not sure what colour pills I would have to be on to conclude that "aqueous solutions" and "not aqueous" were the same
thing but I guess some of you could tell me.
As for "Not really, given that oxidation and reduction are two sides of the same coin." I still think its a bizare state of affairs where
Li+ pops up in a list of oxidisers, technically it is one, and I dare say I could come up with circumstances where Li++ (the doubly charged ion) is an
oxidant too- but it certainly wouldn't be in aqueous solution.
Make up you minds folks- if this thread is is aqueous conditions then Mn2O7 shouldn't be here and nor should Li. If it isn't about aqueous
solutions then my comments about the space shuttle are legitimate.
If you are taking a rather relaxed view on the presence or absence of water, then both comments still stand.
Once you sort that out you might want to think a bit harder about who should be taking the pills.
[Edited on 29-11-2005 by unionised]
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BromicAcid
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But... but... how, if you read non-aqeuous but very reactive next to dimanganese heptoxide did you then read the rest of the list as though all the
reagents were anhydrous even though some specifically say "(sluggish in aqueous media, works only in acidic media)" Perchloric acid is
specifically stated at a concentration of 60% so you couldn't be thinking anhydrous and you probably know from experience the stability of the
perchlorate anion in aqueous solutions. To me it was completely obvious what Woelen ment by his listing although in retrospect looking at it from
your vantage point I could see where the Mn<sub>2</sub>O<sub>7</sub> could complicate things. But I believe there were enough
other pointers in his post that pointed to an aqueous enviorment that would lead many to conclude they were aqueous reactions over non-aqueous
reactions.
Thank's Woelen for that practical list by the way!
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Dr. Beaker
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I must agree with what unionised says, since redox, like many other types of reactions, are highly dependant upon conditions such as gasous or
condensed phas, solvent (water or other) temp and concentrations.
my example on Li+ as oxidizer further strenthen the above mentioned. I speculate that in uncoordinative solvent the naked Li+ ion might be less
stabilized and therefore more prone to reduction.
nevertheless, being right does'nt mean you can be rude. ("call NASA etc."
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unionised
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I read the comments about non aqueous solutions and aqueous ones in the same post as evidence that people were not exclusively dealing with aqueous
(or, indeed, non aqueous) reactions.
What else would I have done?
OK, the joke about 'phoning nasa might have been seen as a bit harsh, but, when it comes down to it I wasn't the first to talk about non
aqueous systems and I was using it to illustrate the fact that reaction rates are so vastly dependent on circumstances that compiling a table of them
is difficult, if not pointless.
On the subject of being rude I'm interested in how else (other than as being rude) one might interpret the "joke" about forgetting the
pills.
The fundamental point I made - that a table of redox potentials gives both the reactant and the product, in addition to defining the conditions
whereas a "speed of reactions" does none of these and will thereore be of limited value doesn't seem to have been addressed.
Of course, I look forward to a reply that addresses this tricky aspect of a ranking by rate of reaction.
[Edited on 30-11-2005 by unionised]
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Dr. Beaker
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I'll not waste my time any more on the issue of who's rude and what is a joke and what is a "joke". and on the subject:
"table of redox potentials gives both the reactant and the product, in addition to defining the conditions whereas a "speed of
reactions" does none of these and will thereore be of limited value"
as I see it "strength" is dependent on:
1. if the reaction is termodinamically spontenious at all under the given conditions (i.e negative delta G)
2. even if we have negative delta G kinetics also play significant role. if only redox potential matter (which are only dependent on delta G since
delta G = -nFE) then the wooden chair you are sitting on will start to burn since combustion of wood is termodinamically favoured... but the
activation energy prevents it.
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neophyte
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Thanks woelen , that is a wonderful list : i have looked for such a list for a long time . It gives me several ideas as to how some natural reactions
occure . With that being said I would expect that one of the titanium salts would be near the top as a very strong oxidizers ( that is just from
observations of where titanium is found in natural mineralogical reactions).
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chemister2015
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My list oxidizers:
fluorine-based
KrF+ > NiF3+ > BrF6+ > AgF2+ > PtF6 > ClF6+
oxygen-based
XeO6(4-) > O3 > S2O8(2-) > Cu2O3 > NpO3 > AmO3 > FeO4(2-) > BrO4(-) > XeO3 > Bi2O5
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AJKOER
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Quote: Originally posted by neophyte  | | Thanks woelen , that is a wonderful list : i have looked for such a list for a long time . It gives me several ideas as to how some natural reactions
occure . With that being said I would expect that one of the titanium salts would be near the top as a very strong oxidizers ( that is just from
observations of where titanium is found in natural mineralogical reactions). |
Actually, in the presence of sunlight and H2O, I recall reading that TiO2 is a source of hydroxyl radicals!
Now, one albeit bias source (they are selling a product generating the OH radical, see http://www.hydrogenlink.com/hydroxylradicalsreactivity ) actually describes the hydroxyl radical as the ultimate oxidation tool!
So, I do agree with Neophyte comment.
Source: See, one of many for example: http://pubs.acs.org/doi/abs/10.1021/jp9505800
[Edited on 12-7-2015 by AJKOER]
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unionised
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It seems unlikely that neophyte will see your reply nearly 10 years after they posted .
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AJKOER
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I guess, we will see.
The reference I cited was actual published in 1996, but internet access was probably latter, so I may have a poor excuse on being late.
I should also note that nano particles of TiO2 are particularly active. See, for example, "Hydroxyl radicals (.OH) are associated with titanium
dioxide (TiO2) nanoparticle-induced cytotoxicity and oxidative DNA damage in fish cells", with abstract available at http://www.sciencedirect.com/science/article/pii/S0027510707... .
I did find his mineralogical viewpoint on possibly assessing chemical reactivity interesting.
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The Chemistry Shack
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I don't know if anyone has responded to you yet, if they have I'm sorry for repeating what they probably said.
Mn2O7 can easily be prepared as long as you have KMnO4 and 98% H2SO4.
Just add enough of the acid to cover the permanganate and you will get the oily green liquid of Mn2O7. It will be difficult to purify and will contain
KMnO4 and H2SO4 impurities. D
An important note is NOT TO STROE THIS COMPOUND. Just make it when you need it. It is nasty stuff, instantly ignites room temperaure organics on fire
on contact, explodes with sulfur on contact, burns plastics...nasty stuff
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chemister2015
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Can anyone check ignite Mn2O7 pyridine, acetonitrile or not?
Sorry for my english.
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ave369
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Where does one put Cu2O3, ferrates and perbromates in the topic's main table?
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DraconicAcid
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It *will* ignite dichloromethane, which is generally considered less flammable than those.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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