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Topic: Reduction and Electrochemistry  (Read 11211 times)

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budullewraagh

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Reduction and Electrochemistry
« on: July 10, 2004, 05:32:55 PM »
can anybody here tell me an effective way to take Mg+2 ions out of a solution of MgSO4?  i am looking for a way to do this using electrochemistry, rather than replacing the Mg+2.

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Re:Reduction and Electrochemistry
« Reply #1 on: July 10, 2004, 08:24:17 PM »
I'm not sure but I think you could do electrolysis on molten MgSO4 but it makes sulfur trioxide gas as well as plating magnesium onto the electrode. Sulfur trioxide is nasty stuff, it forms sulfuric acid on contact with moisture such as mucous membranes, in the air it combines with water vapor to make a very fine sulfuric acid mist and is a component in acid rain. I wouldn’t suggest doing this at home but that’s how they produce magnesium industrially.
« Last Edit: July 10, 2004, 08:25:27 PM by Scratch- »
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budullewraagh

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Re:Reduction and Electrochemistry
« Reply #2 on: July 10, 2004, 08:50:30 PM »
to add to that i would need to melt MgSO4.  that's 1124 celcius anyway so i dont suppose it would work.  aside from your method, is there ANY way to reduce Mg2+(aq) without using replacement?

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Re:Reduction and Electrochemistry
« Reply #3 on: July 10, 2004, 08:56:58 PM »
Only using electrolysis? I think you might be able to do electrolysis on the salt while keeping the two electrodes separate with a conductive barrier such as a piece of paper soaked in the solution and then melt and do electrolysis to the MgOH that would be produced, that would lower the melting temperature and get rid of the sulfur trioxide....  I'm not sure it would work though. Perhaps one of the more chemistry literate people here could clear this up.
« Last Edit: July 10, 2004, 08:59:32 PM by Scratch- »
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budullewraagh

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Re:Reduction and Electrochemistry
« Reply #4 on: July 10, 2004, 09:49:15 PM »
i'm just looking for a way to take Mg+2(aq) out of solution that doesnt involve replacement.  any other way conceivable works.  of course, i am only 15 and thus have limited resources in my basement lab...

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Re:Reduction and Electrochemistry
« Reply #5 on: July 11, 2004, 12:33:46 PM »
giving magenesium relatively high reactivity, it would be hard to even displace magnesium cations from solution. An alternative is to precipitate or something that can faciliate cation exchange with the solution..
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Re:Reduction and Electrochemistry
« Reply #6 on: July 11, 2004, 01:20:47 PM »
I think NaOH would work right? That’s fairly commonly used in drain cleaners and would be available to use without a trip to a chemistry store.
« Last Edit: July 11, 2004, 01:21:53 PM by Scratch- »
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Offline Mitch

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Re:Reduction and Electrochemistry
« Reply #7 on: July 12, 2004, 07:34:38 PM »
Obtain MgOH and do the electrolysis from there. MgSO4 is way to inert.
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budullewraagh

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Re:Reduction and Electrochemistry
« Reply #8 on: July 17, 2004, 05:19:43 PM »
eh, i can't find Mg(OH)2 (you said MgOH but i assume you mean Mg(OH)2) anywhere.  i know that NH3 solutions can reduce alkali metals to form anions.  is it possible to reduce aqueous group 1 and/or 2 metals using a solution of NH3?

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Re:Reduction and Electrochemistry
« Reply #9 on: July 17, 2004, 05:52:37 PM »
eh, i can't find Mg(OH)2 (you said MgOH but i assume you mean Mg(OH)2) anywhere.  i know that NH3 solutions can reduce alkali metals to form anions.  is it possible to reduce aqueous group 1 and/or 2 metals using a solution of NH3?

You will NEVER be able to reduce group 1 metals, as well as the heaver group 2 metals, if they are in an aqeuous solution.  Just think about what you were saying.  Do you think that sodium metal, which reacts violently with water, will be able to exist in its pure state if coming from an aqeuous solution?  As soon as it is formed, it will violently react with the water and go back into solution.  So no; you'll never be able to reduce any of the group 1 and most of the group 2 metals from an aqueous solution using an NH3 solution.   ;D
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budullewraagh

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Re:Reduction and Electrochemistry
« Reply #10 on: July 17, 2004, 06:53:11 PM »
sorry, it's liquid NH3, not NH3 solutions.  none the less, i suppose i could use an alcohol as a solvent, although it would be difficult extracting the NH3 without inhaling anhydrous NH3, no?

Limpet Chicken

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Re:Reduction and Electrochemistry
« Reply #11 on: July 17, 2004, 07:31:17 PM »
Group 1 and 2 metals can be made electrolytically by elecrtolysis of a halide salt in pyridine, lithium can be prepared by doing the same in amyl alcohol I have heard, although I have never tried this, for magnesium the best bet would probably be to fine a very low melting point eutectic salt mix and fuse it, then go electrolyse it from there.

You could probably reduce with Na maybe in a higher alcohol to get Mg,  sodium an be electrolysed out of fused anhydrous NaOH, or better yet find a eutectic, I hear some of the gallium/sodium eutectics melt at an extremely low temperature, about 80 C or something like that :)  

When isolating from fused NaOH, take care to keep the temperature almost EXACTLY the melting point of the hydroxide, do it on a hotplate, i've done it with an ordinary blowtorch because I don't currently have a hotplate and am too lazy to buy one ;D

About 5-10 C above the melting point of NaOH, instead of metallic Na forming, a mettalloid alloy type material of Na dissolved in NaOH can be formed, but if done right, beads of metallic sodium will be formed that can be dug out of the NaOH with a bit of metal/knife or have a looped bit of wire dipped into them while molten, withdraw the wire and flick the beads of sodium into mineral oil for storage.

Eye protection and preferably gloves are a must, don't be scared of the pops and bangs of the beads of sodium that you arent quick enough to flick into oil, the electrolysis calms down somewhat after an initial few minutes ;D

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