Sciencemadness Discussion Board - copper ammonium sulfate

copper ammonium sulfate

Lithium - 11-5-2012 at 02:17

hello

several months ago (possibly a year) i got a 1.5L soda bottle, cut the top off ( cone bit )and filled it with ammonium sulfate crystals to 1/4 of the way. i then added several teaspoons of copper powder(0-5% CuO impurity, no other metal ions) and poured in water until it was full to the brim. ( i was not using the right amounts, i just was excited that 5kg of (NH4)2SO4 turned up, so i played with it a bit )

today it is a deep blue solution, with blue crystals ( 4 or 5 ) from 3-5cm in diameter. the liquid level is down to 1/4 of the way. I understand that CuSO4 has formed, but has the formed ammonia concentrated and formed a complex?

Cu + (NH4)2SO4 ---> CuSO4 + 2NH3

CuSO4 + 2NH3 ----> CuSO4(NH3)2SO4

i know that amine complexes do form with addition of conc. NH3 solution to CuSO4, but i am unsure if it crystalises out.

thanks for replies,
Li

[Edited on 11-5-2012 by Lithium]

weiming1998 - 11-5-2012 at 02:46

Quote: Originally posted by Lithium

hello

several months ago (possibly a year) i got a 1.5L soda bottle, cut the top off ( cone bit )and filled it with ammonium sulfate crystals to 1/4 of the way. i then added several teaspoons of copper powder(0-5% CuO impurity, no other metal ions) and poured in water until it was full to the brim. ( i was not using the right amounts, i just was excited that 5kg of (NH4)2SO4 turned up, so i played with it a bit )

today it is a deep blue solution, with blue crystals ( 4 or 5 ) from 3-5cm in diameter. the liquid level is down to 1/4 of the way. I understand that CuSO4 has formed, but has the formed ammonia concentrated and formed a complex?

Cu + (NH4)2SO4 ---> CuSO4 + 2NH3

CuSO4 + 2NH3 ----> CuSO4(NH3)2SO4

i know that amine complexes do form with addition of conc. NH3 solution to CuSO4, but i am unsure if it crystalises out.

thanks for replies,
Li

[Edited on 11-5-2012 by Lithium]

I am almost certain that it is an ammonium bisulfate contamination, as neither Cu nor CuO can dissolve in (NH4)2SO4 in any way, but CuO (formed by the slow oxidation of Cu in air) might dissolve in a solution of NH4HSO4 according to the following equation:
2NH4HSO4+CuO===>CuSO4+(NH4)2SO4+H2O.
Is the solution a deep copper sulfate blue? Or is it much darker than that?

Lithium - 11-5-2012 at 03:02

you never fail me weiming

the solution is a dark blue colour, but not as dark as the crystals of tetra amine copper sulfate on the wiki page. the solution colour is like a super sat. sol. of CuSO4, i can take a picture if you want, but i would have to use my ipod.

the crystals are not as dark as the solution, and are slightly lighter in colour than my bought CuSO4.

does CuSO4 and (NH4)2SO4 ( or NH4HSO4 ) co-crystalize, because the crysatls look 100% pure, like there are no impurities

there is also some bluish ppt, which i am presuming is Cu(OH)2

CuSO4 + 2NH4OH ----> Cu(OH)2 + (NH4)2SO4

Li

weiming1998 - 11-5-2012 at 05:57

Quote: Originally posted by Lithium

you never fail me weiming

the solution is a dark blue colour, but not as dark as the crystals of tetra amine copper sulfate on the wiki page. the solution colour is like a super sat. sol. of CuSO4, i can take a picture if you want, but i would have to use my ipod.

the crystals are not as dark as the solution, and are slightly lighter in colour than my bought CuSO4.

does CuSO4 and (NH4)2SO4 ( or NH4HSO4 ) co-crystalize, because the crysatls look 100% pure, like there are no impurities

there is also some bluish ppt, which i am presuming is Cu(OH)2

CuSO4 + 2NH4OH ----> Cu(OH)2 + (NH4)2SO4

Li

Hmmm...strange. How could Cu(OH)2 have formed? The impurity NH4HSO4 would have reacted with it. Even if there isn't any more NH4HSO4, no free OH- would exist in solution. I think you should test the precipitate by putting a bit of it in water and boiling it dry. If it was Cu(OH)2, it would turn black.

Maybe some sort of double salt did form between the reaction of CuO and NH4HSO4.

barley81 - 11-5-2012 at 12:18

Ammonium and copper (II) form a double sulfate salt: (NH4

2Cu(SO4

2 · 6H2O.
http://scripts.iucr.org/cgi-bin/paper?S0365110X6500169X

Nicodem - 12-5-2012 at 08:54

Quote: Originally posted by weiming1998

Weiming1998, I would very much prefer it, if you would please stop posting unreferenced and clueless speculative replies (in general, not just this thread!). What exactly is the purpose of your posts? Have you ever considered that members posting in the Beginnings section might not have enough knowledge to comprehend the difference between an unreferenced speculation and a referenced educational explanation? It is thus of utmost importance to provide references (just like barley81 did), rather than post unreasonable speculations like you did. You don't even have any basic knowledge of proton transfer chemistry as your post above demonstrates, yet you don't feel any restrains from posting idle speculation and unreferenced assumptions based on acid/base reactions. Please constrain yourself until you have adopted the forum guidelines for posting.

weiming1998 - 12-5-2012 at 16:28

Quote: Originally posted by Nicodem

Quote: Originally posted by weiming1998

Ok, it is my bad that I did not post any references and speculated instead, but you really don't need to flame like that. I will try and post references instead of speculations in the future.

Edit: I based my claims on the production of the ferrous ammonium sulfate double salt, which is very similar to the copper ammonium sulfate double salt. References: http://www.scienceforums.net/topic/51996-making-copperii-amm...
The production of the ferrous ammonium sulfate salt involves the combination of ammonium sulfate with a littlesulfuric acid, which indicates that ammonium bisulfate has a role to play in this reaction: Reference: http://en.wikipedia.org/wiki/Ammonium_iron(II)_sulfate
Copper (II) oxide certainly reacts to form copper sulfate with ammonium bisulfate, or indeed, any bisulfate. That part is so obvious it requires no references (ok, would posting that water is H2O require any references?)
The copper sulfate doesn't combine with the ammonium sulfate in aqueous solution, being just a a mix of Cu2+, NH4+ and SO4- ions, but when crystallized (as the original poster indicated), it forms a double salt (again Wikipedia article as reference)

I am sorry I did not post any proper scientific journals as references, but that is because they require money, contact with services or cracking off the net in order to read. I am not yet an adult, and my family is poor, so I do not want to spend money off these (also the reason I do not have shelf loads of chemistry books, which can be used as references), so I am stuck with using crappy references off the net (unfortunately)

And one more thing, the angry flame was very much unappreciated.

Edit again: Ok, now I have seen the free resources from the forum guidelines thread. I will attempt to use them in the future.

[Edited on 13-5-2012 by weiming1998]

[Edited on 13-5-2012 by weiming1998]

Lithium - 12-5-2012 at 23:45

the ppt has redissolved for some reason, and i took the crystals out, dried them and stored them in a small plastic container.

they are now sitting on my table ( they look nice )

you can use the books in the library for references ( i have them downloaded onto my ipod and read them when i can )

maybe the ppt was an intermediate such as:

Cu + 2H2O ---) Cu(OH)2 + H2

this rxn is slow, hence the time it took for sol. to turn light blue

Cu(OH)2 + 2NH4HSO4 ----) CuSO4 + 2H2O + (NH4)2SO4

Li

weiming1998 - 13-5-2012 at 00:03

Quote: Originally posted by Lithium

the ppt has redissolved for some reason, and i took the crystals out, dried them and stored them in a small plastic container.

they are now sitting on my table ( they look nice )

you can use the books in the library for references ( i have them downloaded onto my ipod and read them when i can )

maybe the ppt was an intermediate such as:

Cu + 2H2O ---) Cu(OH)2 + H2

this rxn is slow, hence the time it took for sol. to turn light blue

Cu(OH)2 + 2NH4HSO4 ----) CuSO4 + 2H2O + (NH4)2SO4

Li

Copper cannot ever reduce H+ ions to H2, especially if a weak acid like H2O is utilized! I am now combining CuSO4 with (NH4)2SO4 under acidic conditions and see if a double salt can be crystallized out. It is strange that a precipitate would stay intact for several months, but when you observe it, it's gone. Have you changed the temperature or the amount of sunlight the container is exposed to?

Lithium - 13-5-2012 at 02:54

"Copper cannot ever reduce H+ ions to H2, especially if a weak acid like H2O is utilized"

ha, weimming1998, remember that long talk with nicodem about providing references, even with something as obvious as this!

the ppt did not just all turn up, wait, then leave, at first the Cu powder was slowly taken into sol. , it was replaced with the ppt, and the ppt has slowly been diminishing. i only look at the sol. every month or so, but lately have been keeping an eye on it. i was saying the ppt had formed judged on the prevous month's observation. the sol. has not moved for at least half a year, and , as you may have noticed, it has been cooling down at the moment as winter sets in. lowest temp so far is 7-10 degrees celsius.

i might test for a complex by weighing, heating to white ( anhydrous ), forming the pentahydrate, and reweighing. the NH3 lost would be evident in weight difference.

maybe next weekend

Li

[Edited on 13-5-2012 by Lithium]