Upsilon
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Aluminum foil not reacting with CuSO4 solution
I made a fairly concentrated solution of copper(ii) sulfate, and threw some aluminum foil into it. After 2 days, basically nothing has happened. I
added some sulfuric acid to help speed it along, and it greatly sped up the process but only for a minute or so, then it went back to its inactive
state. What is the reason for this?
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DraconicAcid
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Add a chloride source to prevent passivation of the aluminum.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Upsilon
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Ah, thanks, some NaCl really got things going. Why does the presence of chloride ions prevent the aluminum from passivating?
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AJKOER
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OK, this actually is an electrochemical reaction and you need an electrolyte. Salt, NaCl, is a good electrolyte. It can participate in the reaction
but must remain available to aid in ion transfers. In the current context,
2 Al + 3 CuSO4 ----) 3 Cu + Al2(SO4)3
where the Al2(SO4)3 can coat the Aluminum hindering the continuation of the reaction. But, it is dissolved by salt as:
6 NaCl + Al2(SO4)3 = 2 AlCl3 + 3 Na2SO4
and:
2 AlCl3 + 3 H2O = Al2O3 (s) + 6 HCl
so the Sodium and Chloride ions remain in the solution.
[Edited on 27-3-2014 by AJKOER]
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Steam
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I know you got it to work but just so you know when doing chemistry with Al foil to use the cheapest thinnest foil you can find. The thick heavy duty
stuff often contains a thin layer of coating to make it more "non-stick". It also makes it difficult to use as a reducing agent.
DISCLAIMER: The information in this post is provided for general informational purposes only and may not reflect the current law in your jurisdiction.
No information contained in this post should be construed as legal advice from the individual author, nor is it intended to be a substitute for legal
counsel on any subject matter. No reader of this post should act or refrain from acting on the basis of any information included in, or accessible
through, this post without seeking the appropriate legal or other professional advice on the particular facts and circumstances at issue from a lawyer
licensed in the recipient’s state, country or other appropriate licensing jurisdiction.
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macckone
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Quote: Originally posted by Steam  | | I know you got it to work but just so you know when doing chemistry with Al foil to use the cheapest thinnest foil you can find. The thick heavy duty
stuff often contains a thin layer of coating to make it more "non-stick". It also makes it difficult to use as a reducing agent.
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Heavy duty generic brands are seldom non-stick. That non-stick coating adds
cost and generic brands simply don't add it. At least in my experience anything
with a non-stick coating will be clearly labelled as non-stick. Of course your
mileage may vary.
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Steam
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| Quote: Originally posted by macckone | | Quote: Originally posted by Steam | | I know you got it to work but just so you know when doing chemistry with Al foil to use the cheapest thinnest foil you can find. The thick heavy duty
stuff often contains a thin layer of coating to make it more "non-stick". It also makes it difficult to use as a reducing agent.
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Heavy duty generic brands are seldom non-stick. That non-stick coating adds
cost and generic brands simply don't add it. At least in my experience anything
with a non-stick coating will be clearly labelled as non-stick. Of course your
mileage may vary. |
sorry about that, I wasn't clear. The more expensive "Heavy-duty" foils don't react as well has the generic foil does. I am sure there are generic
heavy duty foils that are just fine, but just as a good rule of thumb buy the most simple, plain, generic foil you can find.
In my experience "heavy duty" reynolds has been notorious for giving inconsistent results.
[Edited on 27-3-2014 by Steam]
DISCLAIMER: The information in this post is provided for general informational purposes only and may not reflect the current law in your jurisdiction.
No information contained in this post should be construed as legal advice from the individual author, nor is it intended to be a substitute for legal
counsel on any subject matter. No reader of this post should act or refrain from acting on the basis of any information included in, or accessible
through, this post without seeking the appropriate legal or other professional advice on the particular facts and circumstances at issue from a lawyer
licensed in the recipient’s state, country or other appropriate licensing jurisdiction.
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