Yttrium2
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H2SO4 Drying HCL aq
How exactly does this occur?
does H2SO4 deprotonate into H+ HSO4- have anything to do with it?
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macckone
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Sulfuric acid is hygroscopic.
The solution of water in concentrated acid
Is very exothermic. Because of this the
Thermodynamics push towards dehydration
Of the hydrochloric.
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Yttrium2
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Again, what makes H2SO4 hygroscopic
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Hawkguy
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I don't think that would work if you were using just 35% Hydrochloric Acid since it'd be azeotropic..
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blogfast25
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You can't 'dry' hydrochloric acid solution (HCl(aq)) with H2SO4. But you can dry relatively wet hydrogen chloride gas with conc. H2SO4.
The reason that conc. H2SO4 is hygroscopic is that the solvation energy of pure H2SO4 is very high. See for instance what happens when you pour 98 %
H2SO4 into water: the solution warms up very considerably.
This is due to the formation and solvation of H<sub>3</sub>O<sup>+</sup> ions:
H<sub>2</sub>SO<sub>4</sub>(l) + H<sub>2</sub>O(l) === > H<sub>3</sub>O<sup>+</sup>(aq)
+ HSO<sub>4</sub><sup>-</sup>(aq)
[Edited on 7-2-2015 by blogfast25]
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macckone
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This link has the actual process of dehydrating aqueous HCl.
https://www.erowid.org/archive/rhodium/chemistry/hclgas.argo...
The solution of sulfuric acid does not likely play a role in
this reaction but rather the formation of sulfuric acid hydrates
in the concentrated sulfuric acid.
http://pubs.acs.org/doi/abs/10.1021/ja01486a014
The article gives heats of formation of various hydrates.
The high heats of formation of the hydrates are what make
this possible.
The hemihexahydrate is about 45.6% sulfuric acid by weight.
The above dehydration would only take that to about the
trihydrate based on two volumes of sulfuric acid to one volume
of hydrochloric acid.
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Yttrium2
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Can you explain the last paragraph ^
Please
[Edited on 7-2-2015 by Yttrium2]
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macckone
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If you are doing the method described at erowid in the rhodium archives, then the amount of hydrochloric acid to sulfuric acid
will yield the sulfuric acid trihydrate at the end of the procedure.
The hemihexahydrate would require about twice as much
hydrochloric acid and it is less thermodynamically favorable.
That means that after a certain point you won't get HCl gas.
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Yttrium2
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Won't be doing the method, unless it's the route professionals use. Just was curious about how the drying works. I've never heard of the prefix hemi
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macckone
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Hemihexa - 6.5
Hemi - .5
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Nicodem
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Thread Moved
11-2-2015 at 06:23 |
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