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#Post#: 422--------------------------------------------------
Laboratory preparation of hydrogen chloride gas
DIR By: Chris
Date: July 20, 2012, 6:30 pm
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So in my textbook the equation is
H2SO4 + 2NaCl => Na2SO4 + 2HCl
I know this method works, but my question is why the HCl dosen't
dissolve in the reaction mixture (since it is a solution and
contains water?)
Why does the HCl go off as gas.
Thanks
#Post#: 431--------------------------------------------------
Re: Laboratory preparation of hydrogen chloride gas
DIR By: Edward
Date: July 26, 2012, 3:53 am
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Hello.
As you know the equation is[H2SO4 + NaCl--->NaHSO4 + HCl]
-although there are other theories for this equation- but The
products are NaHSO4 and HCl. what is important here is one of
the products is NaHSO4 and it desires high high[!] heating to
form. As you know in very high temperatures water has a bit
solution and HCl can't dissolve in water(to form acid) and in
fact it even exits as gas .
Hint: HCl(aq) -contains water- is called Hydrochloric acid and
is an strong acid. whereas HCl(g) is Hydrogen-Chloride and it
obviously is a Chloride.
You won't get concentrated hydrochloric if any of your hydrogen
chloride escapes the water at the end before being absorbed. And
hydrogen chloride be more prone to escaping the higher the
concentration gets; as it's solubility decreases.
Eventually I enlighten we can make this equation give us
Hydrochloric, The gas should be bubbled into water using an
inverted funnel to avoid suck-back. but it's not used in
practice for obvious reasons! ;)
Thanks.
#Post#: 433--------------------------------------------------
Re: Laboratory preparation of hydrogen chloride gas
DIR By: Michel
Date: July 26, 2012, 10:21 am
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--- Quote from: Edward link ---
>
> Hello.
> As you know the equation is[H2SO4 + NaCl--->NaHSO4 + HCl]
-although there are other theories for this equation- but The
products are NaHSO4 and HCl.
>
>
--- End Quote ---
depending on the mass ratio of the reactants, the acid salt can
eventually react with more NaCl to produce the normal salt and
more HCl.
#Post#: 435--------------------------------------------------
Re: Laboratory preparation of hydrogen chloride gas
DIR By: PIRAH SALEEM
Date: July 26, 2012, 2:05 pm
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may be due to difference in specific gravity
#Post#: 446--------------------------------------------------
Re: Laboratory preparation of hydrogen chloride gas
DIR By: Chris
Date: July 28, 2012, 4:10 am
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Thanks for replies, but I'm still confused.
--- Quote from: PIRAH SALEEM link ---
>
> may be due to difference in specific gravity
>
>
--- End Quote ---
How does specific gravity affect this? NaCl is denser than
water, yet it always dissolves in water.
My question is:
Since all the reactants are dissolved in water, why dosen't any
HCl produced immediately dissolve in the water?
Thanks in advance for replies
#Post#: 447--------------------------------------------------
Re: Laboratory preparation of hydrogen chloride gas
DIR By: PIRAH SALEEM
Date: July 28, 2012, 1:30 pm
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I think due to state, NaCl is solid and HCl is liquid......am
not sure about this but may be
#Post#: 448--------------------------------------------------
Re: Laboratory preparation of hydrogen chloride gas
DIR By: Michel
Date: July 28, 2012, 2:28 pm
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--- Quote from: Chris link ---
>
>
> My question is:
> Since all the reactants are dissolved in water, why dosen't
any HCl produced immediately dissolve in the water?
> Thanks in advance for replies
>
--- End Quote ---
The reactants are all dissolved in water, true, but due to the
Concentrated sulfuric acid, most of the H2O molecules are
attached to the H+ ion to form the H3O+ ion, so the actual
concentration of H2O is low.
Also, HCl is a volatile product and its solubility at high
temperatures is low. And then if you consider the equilibrium
HCl + H2O <==> H3O+ + Cl-
At the start of this reaction, the H3O+ concentration is very
high, due to the concentrated sulfuric acid present, and the Cl-
concentration is also very high due to the Sodium Chloride
present, hence you would expect the Kc of the reaction to be
very high, and much HCl as a gas won't dissolve.
Finally, the reaction itself has a % yield, so in practice, you
won't get the exact stoichiometric amount of HCl(g) as a
product.
#Post#: 467--------------------------------------------------
Re: Laboratory preparation of hydrogen chloride gas
DIR By: Chris
Date: August 2, 2012, 4:31 am
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Thanks Michel
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