artemov
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HCl acid in situ
Is it possible to make HCl acid in situ from sulphuric acid and common salt?
From my calculation (hopefully it's correct), battery acid (37% sulfuric acid) would stoichiometrically give me 30.4% HCl acid. I can put it in the
freezer to precipitate out the sodium sulfate and also ensure the HCl gas stays dissolved. Either decant or cold filter afterwards to get my HCl acid.
Would this work?
So far everything I have read involved generating HCl gas which is then dissolve in water.
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Fery
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HCl pKa = some sources -6.3, other sources -8
H2SO4 pKa1 = some sources -10, other sources -3, other sources -2...
H2SO4 pKa2 = +1.9
so no Na2SO4 formed when mixing 37% H2SO4 with common salt like NaCl
NaHSO4 formed instead
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PirateDocBrown
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Quote: Originally posted by Fery  | HCl pKa = some sources -6.3, other sources -8
H2SO4 pKa1 = some sources -10, other sources -3, other sources -2...
H2SO4 pKa2 = +1.9
so no Na2SO4 formed when mixing 37% H2SO4 with common salt like NaCl
NaHSO4 formed instead |
Hmm, where do you think the chlorine goes?
Phlogiston manufacturer/supplier.
For all your phlogiston needs.
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artemov
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So the reaction is
H2SO4 + NaCl -> NaHSO4 + HCl ?
But isn't NaHSO4 + NaCl -> Na2SO4 + HCl used to make HCl as well?
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Fery
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yes
you can neglect the second reaction because pKa2 of H2SO4 = 1.9 and you have very strong acidic solution with pH certainly less than 0
the direction of the reaction is not from left to right but from right to
left
solubility of NaHSO4 in water is higher than Na2SO4 so putting your solution into freezer is not the right way to go
perhaps BaCl2 could be better (BaSO4 very low solubility) but why to waste BaCl2 when HCl is much more cheaper than BaCl2 and you should also
recalculate whether ever Ksp of BaSO4 overpowers pKa2 of H2SO4 so BaSO4 (s) would be formed and not only Ba(HSO4)2
or if your goal is to obtain HCl for some organic reaction maybe you can extract it from the mixture using some organic solvent in which HCl is
soluble and which is immiscible with water?
or maybe NaHSO4 present in the solution would not cause any problem for the reaction for which you want to obtain HCl (aq) ?
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artemov
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Thanks Fery. Either I will distil off the HCl or use it as it is ... I want to make CrCl3 from chromium metal and HCl, eventually leading to
chromate/dichromate.
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