Chemical Forums
Specialty Chemistry Forums => Citizen Chemist => Topic started by: NinjaLama on January 06, 2010, 01:11:58 PM
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Hello.
I recently saw a video on how to make sulfuric acid from copper sulfate electrochemically. Here is the video: http://www.youtube.com/watch?v=5dUSF9Gl0xE
This is done be electrolysing copper sulfate using an inert electrode.
I have a small sciene project going on, and it would be very intresting for me if it was possible to use the same or a similar method as the one above to make sulfuric acid from other sulfate salts, like magnesium sulfate. Could this be achieved? One problem that i might think will occur is that the magnesium metal would just redissolve in the acid?
I know making sulfuric acid is probably more expensive and much more time consuming than just buying the acid, but i do this mostly becaues I am intrested in the chemistry, not to get large quantities of sulfuric acid.
Hopefully i will some help here, and find out if it is even doable:)
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This can be done, but you will need to use a partitioned cell. Something such as a sealed off terracotta pot should do the job as far as I know. Keeping the MgSO4 on one side, and an inert electrolyte on the other side - This should allow some the Mg+2 ions to flow over to one part, while leaving the SO4-2 in the solution.. or vice versa -- honestly I am not to sure how it works, but I know a partitioned cell out of a terracotta pot, or tyvek should allow you to produce Mg(OH)2 on one side, and H2SO4(aq) on the other side.. Though I may be wrong..
You might have better luck when it comes to responses if you try indiescience (my site - a few chemists there) or sciencemadness, which has lot of very smart people, but make sure you search first and write well - as well as perhaps come up with a reference or idea about how you might go about doing this.. otherwise you may get some trolling comments.
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Mg reduction potential is higher than that of water, that means you will electrolyze water - and the trick is to remove metal replacing it with H+. As you are reducing water instead of metal, solution becomes more concentrated, but pH doesn't change.
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Hmm, It could be reduced out of ethanol, or THF similar to the method used to make rieke magnesium.
but I am not sure if the magnesium can be taken out and then the solution can be quenched with some water and then distilled to obtain the sulfuric acid.
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Has anyone tried this method yet? Also, the only two electrodes that he used were the carbon and the platinum ones. Why do other metals not work? e.g. Aluminum? Silver?
Also, what percentage of H2SO4 would this produce(before distilling it)? Copper Sulfate is pretty cheap and it would be nice to be able to make 500ml of H2SO4 for a reasonable price.
And thank you for having these forums available!
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Electrolysis of magnesium sulfate wouldn't make sulfuric acid because magnesium is too reactive to be formed at the cathode instead of hydrogen. The magnesium sulfate would stay in solution, with the water being electrolysed into hydrogen at the cathode and oxygen at the anode. Copper sulfate works because copper is less reactive than hydrogen, so copper is formed at the cathode, and the H+ ions combine with the SO42- to make sulfuric acid. Then oxygen is formed at the anode.
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I concur with Jango. I use magnesium sulfate as an electrolyte when producing hydrogen gas from electrolysis for that exact reason.
Also, correct me if I'm wrong here, I think copper sulfate is preferred because the copper metal, which gets reduced at the anode, does not react with sulfuric acid so that reaction isn't in competition with the electrolysis. This is in comparison to perhaps iron sulfate which I would not expect to be capable of producing sulfuric acid for that reason.
As lead is highly resistant to sulfuric acid, I would expect lead sulfate to be capable of producing sulfuric acid during electrolysis but it isn't nearly as soluble in water as copper sulfate is.
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Sorry, I meant to say the copper is reduced at the cathode. I get lysdexic, lol.