Charles Boyle
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Synthesis of HCl (acid) and NaOH through electrolysis of NaCl solution.
Hello ScienceMadness community.
I am an aspiring home-chemist who is interested in the chemistry involved in electrolysis.
I performed a quick forum search and found no definite answer to my specific questions.
I am interested in the chemistry involved in synthesizing these two key components in many reactions as well as for other processes involved in
chemistry such as hygroscopic chemicals (like NaOH) for desiccating purposes.
Now to the meat of the thread, I was wanting to inquire how viable it is to reverse the common reaction of HCL + NaOH --> NaCL + H2O and do 2NaCL +
2H2O --> H2 + Cl2 + 2NaOH instead.
I know it is not the most efficient way to obtain either chemical, but I am more interested in the chemistry than obtaining a large amount of either.
Here comes the first obstacle, from my research on the electrolysis of sodium chloride solution, unless the electrodes are spaced far apart, or
separated by an ion membrane, the chlorine gas tends to bond with the NaOH to produce NaClO. To prevent NaCLO formation, the advice I have read was to
cool down the sodium chloride solution beforehand, but wouldn't that likely produce more NaCLO since the solubility of Cl2 in water increases as
temperature decreases (as with most gases)?
The second obstacle comes with collecting both the H2 gas and the Cl2 gas (in a well ventilated area of course) and having them form the notoriously
reactive covalent bond, and then having a way to capture the HCl and pass it through some distilled water to create hydrochloric acid.
Any help in my understanding of these concepts would be greatly appreciated.
I don't fully understand how Cl- ions would react with Na+ ions and the OH- ions to produce NaCLO.
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hissingnoise
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When chlorine dissolves in water, it reacts to form two acids; Cl<sub>2</sub> + H<sub>2</sub>O ---> HCl + HOCl.
Sodium reacts to neutralise both acids, obviously, and the salts; NaCl and NaClO are produced!
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Charles Boyle
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Okay, that makes perfect sense.
Wouldn't heating up the NaCl solution prevent some Cl2 gas from redissolving back into the solution?
Also, what would be a safe way to isolate the H2 and Cl2 gases and then have them react with each other?
From what I've read and seen, the reaction is rather violent.
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Bot0nist
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An equal molar mix of hydrogen and chlorine will react to form HCl in an extremely violent explosion when exposed to light, I believe. I can't find
the post right now, but I have read on this site that an experiment was done with Cl<sub>2</sub> and H<sub>2</sub> mixes being
exposed to different wavelengths of light and that some wavelengths resulted in the explosive formation of HCl and some did not provoke the reaction.
I will try to search for it.
I doubt it is a feasible or sane way to synthesize HCl, if that's what your going for...
[Edited on 15-10-2011 by Bot0nist]
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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Polverone
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Look up electrodialysis. It can perform the separation of neutral salts into acidic and basic components without the roundabout trip through gaseous
products.
PGP Key and corresponding e-mail address
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ThePhDChemist
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I will do just that, I tried it and it works!!
Just subscribe to me on youtube
youtube.com/thephdchemist
I am manafacturing hydrochloric acid, sodium hydroxide, hypochlorite, chlorate, perchlorate andchlorine every day with that, i will record soon.
So subscribe 
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Charles Boyle
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So the production of HCl this specific way is not really an option for the average home chemist without access to ion-exchange membranes?
But it is still a viable method of obtaining NaOH, correct?
As long as you keep chlorine gas from dissolving back into solution.
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Imran
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What about this:
Make SO2 and then bubble and dissolve it in the water. Then electrolyse NaCl and bubble Cl2 gas into SO2 solution. You will get sulfuric acid and hcl.
Than distill hcl and u will have HCl and H2SO4.
Cl2+SO2+2H2O=H2SO4+2HCl
PS: English is not my 1. language so there are maybe some mistakes in the text above
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jsc
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Doing this is a pain in the ass. If you are interested in this kind of process go to Google books and find old chemistry texts which will show you an
apparatus.
A much easier way to synthesize sulfuric acid, purify it, then use it to generate HCL by reacting with salt. You can also get sulfuric acid from auto
parts or battery stores because it is used to refill batteries.
The apparatus to synthesize sulfuric acid is complicated, but a lot easier than an electrochemical setup for HCL. The following book describes how to
prepare sulfuric acid in the laboratory:
Laboratory methods of inorganic chemistry
By Heinrich Biltz, Wilhelm Biltz, William Thomas Hall, Arthur Alphonzo Blanchard (1909) pp 49-53. Get on Google Books.
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