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Ramium
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Copper hydroxide synthesis question
I am trying to make copper hydroxide.
In the electrolysis method i saw on youtube, they used a 16 v 3 amp power pack. What is the minimum voltage needed for this to work ( eg could i use a
12 v battery?)
[Edited on 4-12-2014 by Ramium]
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Bert
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Thread Moved
3-12-2014 at 23:02 |
Bert
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gdflp
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http://www.sciencemadness.org/talk/viewthread.php?tid=24174 This might be useful for you. To answer your question directly, yes a 12V battery
would provide a high enough voltage.
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Ramium
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Thank you!
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Ramium
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I made copper hydroxide by adding a solution of NAOH to a solution of CUSO4 i dried the pricipitated Copper hydroxide in the sun but it turned to
copper oxide. I read somewhere that copper hydroxide when heated turns to copper oxide so i thought when i try the experiment again I could evaporate
it in a cold place and it shouldent turn to copper oxide is this so???????????????
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woelen
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A much lower voltage than 12 V is better. Use 5 V. That will give better results. With 12 V you could put 2 cells in series in order to have double
speed. With 16 V you even could put 3 cells in series. Use bigger electrodes if you use cells in series in order to keep the resistance sufficiently
low.
Copper hydroxide is only marginally stable. It very easily loses water and then it forms CuO. Even when stored under water, it can lose water. In
practice, I would forget about copper hydroxide. Isolating the dry pure material is very difficult and it certainly will turn dark due to partial loss
of water. Even when stored at room temperature, it will slowly turn to copper oxide.
So, you could also turn your project into making pure copper oxide. If you want to do that, then make copper hydroxide, suspended in water and rinse
this to get rid of all kinds of other ions and then heat, while stiull under water. The precipitate then turns black and becomes more coarse and
easier to separate from the water. You should even boil it some time. This makes the precipitate more compact and the boiling also assures that more
other ions are leached out of the solid material. Then finally, you can filter and dry the black material.
This black material is a great source for other copper compounds. It dissolves easily in nearly every acid. Copper(II) oxide is one of the few metal
oxides which does not become inert on heating and on storage.
[Edited on 22-1-15 by woelen]
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Ramium
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The electrolysis product seems quite stable but the predipitate product sounds unstable from what you described but it's the same chemical isn't it?
So how can they be different in stability??????
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Ramium
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The copper hydroxide in this video is quite stable as it is not turning even slightly black
http://youtu.be/YsZodLOJnX8
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Amos
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I've found that the precipitate from using sodium hydroxide and a copper salt is very unstable, but if aqueous ammonia is used instead with an excess
of copper sulfate, the product is stable pretty much indefinitely and is quite thermally stable too.
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DraconicAcid
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I have a big jar of it that the college bought from Sigma or Aldrich. It seems perfectly stable as a dry powder.
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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Ramium
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Could you tell me how i could make copper hydroxide without it decomposing and with out electrolysis????
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Ramium
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Quote: Originally posted by No Tears Only Dreams Now  | | I've found that the precipitate from using sodium hydroxide and a copper salt is very unstable, but if aqueous ammonia is used instead with an excess
of copper sulfate, the product is stable pretty much indefinitely and is quite thermally stable too. |
Aqueous ammonia used instead of what?
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DraconicAcid
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| Quote: Originally posted by Ramium | | Quote: Originally posted by No Tears Only Dreams Now | | I've found that the precipitate from using sodium hydroxide and a copper salt is very unstable, but if aqueous ammonia is used instead with an excess
of copper sulfate, the product is stable pretty much indefinitely and is quite thermally stable too. |
Aqueous ammonia used instead of what?
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Instead of sodium hydroxide. Just don't add an excess, or it will dissolve as a complex ion.
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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Amos
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I must also add that copper(II) chloride should not be used as the copper salt, or copper oxychloride will also form. Best to stick with good ol'
copper sulfate.
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blogfast25
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Freeze or vac dried, I'm guessing.
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Amos
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Not necessarily. Like I said, the kind I make with ammonia is light blue and very easily dries under a fan at 90C, or more slowly in air.
[Edited on 1-26-2015 by No Tears Only Dreams Now]
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blogfast25
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Can you describe your experimental procedure more accurately? Have you determined your product's composition?
[Edited on 26-1-2015 by blogfast25]
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Ramium
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| Quote: Originally posted by No Tears Only Dreams Now | | I've found that the precipitate from using sodium hydroxide and a copper salt is very unstable, but if aqueous ammonia is used instead with an excess
of copper sulfate, the product is stable pretty much indefinitely and is quite thermally stable too. |
What are the quanties of ammonia and copper sulphate?
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blogfast25
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If you use fairly dilute NH3 and make sure not to exceed the NH3 stoichiometry of:
Cu2+ + 2 NH3 + 2 H2O === > Cu(OH)2(s) + 2 NH4+
... then only cupric hydroxide will form.
But with strong ammonia in excess then:
Cu(OH)2(s) + 4 NH3 === > [Cu(NH3)4]<sup>2+</sup>(aq) + 2 OH-
... will occur.
So keeping the molar ratio NH3/Cu2+ below 2 should result in Cu(OH)2 only.
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Ramium
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I brought some Ammonia at the supermarket i looked on the back and it said it was ammonium hydroxide could i use ammonium hydroxide instead of
ammonia???????????
Sorry if this is a stupid question
[Edited on 27-1-2015 by Ramium]
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blogfast25
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| Quote: Originally posted by Ramium | I brought some Ammonia at the supermarket i looked on the back and it said it was ammonium hydroxide could i use ammonium hydroxide instead of
ammonia???????????
Sorry if this is a stupid question
[Edited on 27-1-2015 by Ramium] |
There is no such thing as 'ammonium hydroxide', that is an old and obsolete term you'll still find (but increasingly rarely) in some technical
documentation.
What you bought was a solution of ammonia (NH<sub>3</sub> in water (you
did not specify any concentration although the bottle normally will).
When ammonia is dissolved in water the following chemical equilibrium is established:
NH3(aq) + H2O(l) < === > NH4<sup>+</sup>(aq) + OH<sup>-</sup>(aq)
... because ammonia is a weak alkali. Most ammonia in the solution is present as actual NH3, only a very small proportion of it is present as
NH4<sup>+</sup>(aq) + OH<sup>-</sup>(aq).
[Edited on 27-1-2015 by blogfast25]
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Ramium
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Its 18 grams ammonia per litre of water. Would it work in the experiment?????
[Edited on 27-1-2015 by Ramium]
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blogfast25
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Tell me EXACTLY what it says on the label. Taking the value you cite at face value would mean a NH3 molarity of about 0.5 mol NH3 / litre of solution.
That's very low for a commercial NH3 solution (but not impossible)
Describe the experiment you are planning to conduct.
[Edited on 27-1-2015 by blogfast25]
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Ramium
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It says ammonium hydroxide approximately 18/L.
I plan react it with copper sulphate to produce copper hydroxide
So would it work in the experiment??????
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Amos
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Yes, that would work, and be sure to use stirring while the ammonia is being added(you must add ammonia to copper sulfate, not the other way around)
to keep any complex from forming. You should use small amount less ammonia(you'll need to do your own calculations there) than would be needed to
fully react with the copper sulfate, leaving behind a dilute solution of copper sulfate on top of your precipitate.
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