chornedsnorkack
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Fluoroantimonic acid azeotrope
What is the azeotropic boiling point and composition of fluoroantimonic acid?
The pure substances, to remind, are:
HF boils at +19,5 degrees, and obviously very resistant to any thermal decomposition
SbF5 boils at +149,5 degrees. And also resistant to thermal decomposition.
So... do HF and SbF5 release any heat on adding HF to excess of SbF5, like happens on e. g. mixing H2O and SO3, or H2O and HCl?
Do HF and SbF5 form a high boiling azeotrope?
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blogfast25
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I hope you don't plan on messing with that kind of stuff!
Since as HF + SbF5 ===> HSbF6 is spontaneous, ΔG < 0.
ΔG = ΔH - TΔS, so it's a reasonable expectation that ΔH < 0.
Stuff about a HSbF6/HF azeotrope belongs in specialist literature, I think.
Actually it's H2F[SbF6]... Any phase diagram would be between that and HF.
[Edited on 24-2-2015 by blogfast25]
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chornedsnorkack
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Quote: Originally posted by blogfast25  |
Stuff about a HSbF6/HF azeotrope belongs in specialist literature, I think.
Actually it's H2F[SbF6]... Any phase diagram would be between that and HF.
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Phase diagram should go all the way to SbF5. After all, it is SbF5 which boils only at 149,5 degrees.
When you want to mess with HF, with its inconveniently low boiling point and noxious character of its vapours, your options include a dilute solution
of HF in H2O, boiling point 100 degrees against HF-s 19,5. Well, turns out that HF actually interacts so strongly with water that it forms an
azeotrope boiling at 111 degrees and containing 36 % HF.
So... does SbF5 hold on to small amounts of HF? And does it do so well as to form an azeotrope boiling even higher than the 149,5 degrees of pure
SbF5?
Also, how about the HF complexes with low-boiling fluorides? HF boils at 19,5 degrees, but for example BF3 at -100 degrees. Does BF3 dissolve in HF
and manage to raise its boiling point at least somewhat from that 19,5 degrees?
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chemister2015
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Mixture SbF5 with HF is nonazeotrope.
Information from the book: Azeotropic Data II. - 1962
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