MosinNOUGAT
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So what the hell happened?
Hey,
I was making some copper (II) nitrate by tossing some copper into nitric acid. Everything is going fine until I evaporate all the water off with a hot
plate.
A bunch of NO2 came off the beaker, and I was eventually left with a dry crust of a light, sky blue color. I believe it is "basic" copper nitrate, but
I can't tell for sure.
There was also a black, hard crust at the bottom.
Could I still use this to make copper hydroxide?
Thanks!
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elementcollector1
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That's copper(II) oxide, CuO. It forms as a result of decomposition by heat of your copper nitrate, which is probably the sky blue crust.
Generally speaking, it's considered good practice when crystallizing something out from solution to get to saturation (boil it down pretty far, but
not all the way), leave a bit of water in the hot flask and let it cool, unless you're trying to dehydrate/decompose your target as well. Once cooled,
the saturation concentration will drop and you'll get a precipitate of whatever it is you were going for, as well as possibly some leftover liquid
that you can then repeat the process on. Good math beforehand will always help you pinpoint the exact volume left at which you can turn off the heat
(though it's not strictly necessary and I'm pretty sure most, including me, don't bother).
As for making copper hydroxide from this, the sky blue nitrate is still fine (assuming it's not insoluble from being 'basic'-ified, in which case just
add a bit more acid in with the water) - just dissolve it in fresh, distilled water, put some dilute NaOH, NH4OH or KOH solution in there,
and be sure to keep it away from air (copper hydroxide decomposes to copper oxide and water upon exposure to air for a while). The black oxide,
though, is a step too far - and you can't exactly rehydrate it to the hydroxide. You'll have to put some more nitric acid in and start over for that
stuff.
EDIT: Noticed it was your first post - welcome to ScienceMadness, by the way!
[Edited on 3/12/2019 by elementcollector1]
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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Amos
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Is there something you actually require copper(II) hydroxide for? Usually we know of other routes for preparing copper(II) compounds here, often from
something a little less clumsy than such an unstable compound.
If you really want to isolate copper(II) nitrate here, filter out any insolubles from your mixture and then dry it in a desiccator over an alkali
metal hydroxide (NaOH or KOH).
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diddi
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it seems you have cooked it.
also can i suggest adding the nitric acid slowly once you are almost out of copper. i think you probably had way too much acid.
Beginning construction of periodic table display
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phlogiston
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Why would you even want to crystallize the copper(II)nitrate? You could precipitate the hydroxide from the initial solution (add enough hydroxide to
neutralize the excess acid ).
The only reason I can think if is that you were hoping to purify the copper salt by crystallization, but if that was the purpose, you'd probably
better pick another salt than the nitrate (which is unstable/very unconvenient to work with). And it does not match with your plan to evaporate to
dryness (which you'd not do if you were recrystallizing).
Also, it would be much easier to use copper of good purity to start with, which is not very difficult to acquire.
[Edited on 12-3-2019 by phlogiston]
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"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
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XeonTheMGPony
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Long story short you decomposed your product.
Copper Nitrate is near Impossible to dry, it likes water way too much, to dry it with out decomposing takes a good deal of effort, I'd say vacuum
desiccation
You can return to Copper Nitrate by adding dilute nitric acid and warming on the hot plate, most copper pipe is pretty pure so doubt that is of any
issue!
I just keep my Nitrate in liquid form in the freezer (Unnecessary really) I make tons of it as a useful way of getting rid of weak nitric acid
solutions and to recover any Mercury from making Mercury nitrate.
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maldi-tof
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Quote: Originally posted by XeonTheMGPony  | Long story short you decomposed your product.
Copper Nitrate is near Impossible to dry, it likes water way too much, to dry it with out decomposing takes a good deal of effort, I'd say vacuum
desiccation
You can return to Copper Nitrate by adding dilute nitric acid and warming on the hot plate, most copper pipe is pretty pure so doubt that is of any
issue!
I just keep my Nitrate in liquid form in the freezer (Unnecessary really) I make tons of it as a useful way of getting rid of weak nitric acid
solutions and to recover any Mercury from making Mercury nitrate. |
Hi,
Why do you say that? I mean, the drying part. I have made several times this product, and after centrifugation of the solution, the crystals were
dried without incidences.
Or, as copper nitrate crystallizes with 3 water molecules, you mean get rid of them and obtain the anhydrous form?
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DraconicAcid
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Copper(II) nitrate trihydrate will crystallize from nitric acid solution, but it's very difficult to crystallize from water. I've had some crystals
of it melt on a warm, humid day, and they never resolidified.
Getting it anhydrous is not possible without decomposition.
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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WGTR
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I recently made some copper nitrate with leftover nitric acid and copper wire. Our weather is too humid for drying out this kind of a salt; it never
solidifies. In a desiccator, however, it did crystallize. After several days the atmosphere in the desiccator turned brown from NO2
fumes, and brown traces of decomposition were becoming apparent in the salt, as it was drying out too much. I agree with DraconicAcid that the salt
decomposes before it will go anhydrous under those conditions.
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