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Author: Subject: Something strange happened to my CuSO4 solution
burgies1229
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[*] posted on 10-2-2021 at 06:52
Something strange happened to my CuSO4 solution


I am a beginner to chemistry and decided to make some CuSO4 crystals.
I started by dissolving 300g of CuSO4 into about 400ml of distilled water.
I then boiled the solution down to about 175ml. After letting it cool there was a strange precipitate that formed in the solution.
It is insoluble and sank to the bottom. Crystals are growing on this substance.
Does anyone have an idea of what it is and why it formed?

EDIT: After letting the solution sit all of the substance was gone and had turned into CuSO4 crystals

[Edited on 11-2-2021 by burgies1229]
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draculic acid69
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[*] posted on 10-2-2021 at 07:24


Did U make this from copper wire and sulfuric acid?
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clearly_not_atara
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[*] posted on 10-2-2021 at 07:32


^to what he said, it sounds like an impurity in your CuSO4, assuming you really did use distilled water.

Can you describe the "strange precipitate"? Was it colorless? Brown? Some interesting color?




[Edited on 04-20-1969 by clearly_not_atara]
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Bedlasky
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[*] posted on 10-2-2021 at 07:38


Commercial copper(II) sulfate often contain some insoluble residue, which is probably mixture of copper(II) hydroxide and basic copper(II) carbonate.



If you are interested in aqueous inorganic chemistry look at https://colourchem.wordpress.com/main-page/

I can offer GC analysis of samples. Just U2U to me for more info.

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burgies1229
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[*] posted on 10-2-2021 at 11:14


Quote: Originally posted by clearly_not_atara  
^to what he said, it sounds like an impurity in your CuSO4, assuming you really did use distilled water.

Can you describe the "strange precipitate"? Was it colorless? Brown? Some interesting color?



I used some CuSO4 I bought online.
Reading other replies I think its safe to say it is some impurity.
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Maurice VD 37
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[*] posted on 10-2-2021 at 13:38


Your precipitate may be partially dehydrated copper sulfate. I see that you have concentrated you solution to a huge degree. Commercial copper sulfate has the formula CuSO4·5H2O. But it looses 4 H2O at 110°C to form CuSO4·H2O which is nearly white, pale blue. That is probably what you have obtained.
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DraconicAcid
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[*] posted on 10-2-2021 at 15:09


Quote: Originally posted by Maurice VD 37  
Your precipitate may be partially dehydrated copper sulfate. I see that you have concentrated you solution to a huge degree. Commercial copper sulfate has the formula CuSO4·5H2O. But it looses 4 H2O at 110°C to form CuSO4·H2O which is nearly white, pale blue. That is probably what you have obtained.


After he dissolved it in distilled water? Not a chance.

It's more likely that he's formed some basic copper(II) sulphate just from hydrolysis of the copper 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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burgies1229
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[*] posted on 12-2-2021 at 17:58


Quote: Originally posted by DraconicAcid  
Quote: Originally posted by Maurice VD 37  
Your precipitate may be partially dehydrated copper sulfate. I see that you have concentrated you solution to a huge degree. Commercial copper sulfate has the formula CuSO4·5H2O. But it looses 4 H2O at 110°C to form CuSO4·H2O which is nearly white, pale blue. That is probably what you have obtained.


After he dissolved it in distilled water? Not a chance.

It's more likely that he's formed some basic copper(II) sulphate just from hydrolysis of the copper ion.

I have a few beginner questions here

1. After letting the solution sit, the substance turned into CuSO4 crystals. I am just a beginner but could it have been dehydrated CuSO4 that rehydrated after I let it sit?

2. How does me dissolving it in distilled water make a difference?
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Maurice VD 37
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[*] posted on 13-2-2021 at 03:18


1. Dehydrated copper sulfate can of course rehydrate in the presence of water.
2. Dissolving copper sulfate into distilled water makes a clear solution. Dissolving it into tap water makes a cloudy solution, as tap water contains some HCO3^- ions that reacts with copper ions, producing some basic copper carbonate which is not soluble into water.
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RustyShackleford
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[*] posted on 13-2-2021 at 04:18


Commercial/garden grade copper sulfate has carbonate and sometimes a waxy residue (of yellow apperance) that has to be filtered out for crystallization
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TriiodideFrog
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[*] posted on 14-2-2021 at 21:11


Online chemicals are usually not very pure. I suggest buying from some reputable chemical suppliers.
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draculic acid69
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[*] posted on 15-2-2021 at 06:04


Quote: Originally posted by TriiodideFrog  
Online chemicals are usually not very pure. I suggest buying from some reputable chemical suppliers.


At ten times the price.
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[*] posted on 20-2-2021 at 15:52


Quote: Originally posted by TriiodideFrog  
Online chemicals are usually not very pure. I suggest buying from some reputable chemical suppliers.
Normally I would suggest that too, but not for copper sulfate. It's too easy to purify. The stuff I've bought OTC as root killer hasn't even been noticeably impure, and if it was, a quick recrystallization should remove anything undesirable that would be present.



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