Sciencemadness Discussion Board

Awkward reaction

Eddygp - 14-11-2012 at 10:34

Lacking sodium carbonate, I tried to react copper sulfate and sodium bicarbonate to make copper carbonate. i then had the idea to add some diluted H2O2 at 5% conc. or so to the mixture.

It almost instantly started fizzing. I could not recognize any smell, but it all changed to a dark brown solution. What have I created? Some sort of weird sodium cuprate?

EDIT: Actually, it was a suspension of incredibly fine black particles in a greenish solution. I believe the blackish powder is cupric oxide, but... the green solution?

[Edited on 14-11-2012 by Eddygp]

Eddygp - 14-11-2012 at 14:01

Green-bluish solution. Not quite the colour of CuSO4.

bbartlog - 14-11-2012 at 18:16

Stoichiometry? Was there any precipitate prior to the addition of H2O2? I would expect some sort of cupric carbonate (blue) to precipitate. As for the green color, no idea. Maybe the dissolution of other ions (sodium sulfate etc.) changes the color chemistry of the copper somehow.

chemrox - 14-11-2012 at 19:06

http://en.wikipedia.org/wiki/Copper
you oxidized it with the peroxide as you might have expected

CHRIS25 - 15-11-2012 at 03:25

You can also get sodium carbonate by simply heating the sodium bicarbonate in an oven, it will drive off the water. Then that's it.

vmelkon - 15-11-2012 at 06:57

There is this thread from 2005
http://www.sciencemadness.org/talk/viewthread.php?tid=4866

Eddygp - 15-11-2012 at 14:33

Th solution was actually blue, meaning there is some unreacted CuSO4.
And by the way, I searched for topics bearing the name CuSO4. I am sorry if I opened a topic similar to that one, but as I found any of these characteristic having CuSO4 in its name or text... :cool:

[Edited on 15-11-2012 by Eddygp]

UnintentionalChaos - 15-11-2012 at 14:41

When I last tried to precipitate CuSO4 solution with NaHCO3, the solution turned a dark blue- darker than the original CuSO4. Presumably, this was a soluble carbonato complex of some sort. I'm unsure about following the H2O2 addition, though.

tetrahedron - 15-11-2012 at 14:47

carbonayto, carbonahto

sargent1015 - 15-11-2012 at 15:13

If you heat the CuSO4 and bicarb while mixed in solution, you will get the carbonate.

vmelkon - 16-11-2012 at 06:47

You don't need to heat it. CuCO3 forms right away while CO2 bubbles off. Most bicarbonate are unstable and decompose to carbonate and CO2.
The alkali metal bicarbonates are stable, in solution and solid form.
The alkali earth metal bicarbonates are stable in solution (cold) but I think they can't be isolated in solid form.

CuSO4 + 2 NaHCO3 -> CuCO3 + Na2SO4 + CO2 + H2O

Eddygp - 16-11-2012 at 11:35

By the way, any method to test for SO2?

tetrahedron - 16-11-2012 at 13:14

allegedly SO2 reacts with MnO2 to give MnSO4.

ElectroWin - 17-11-2012 at 12:47

SO2 gas is also smelly.. it has that brimstone smell. it should be obvious if you make some.

Eddygp - 17-11-2012 at 13:15

Yes, I mean, it emits a really pungent odor, choke-like

tetrahedron - 19-11-2012 at 06:22

Quote: Originally posted by Eddygp  
it emits a really pungent odor, choke-like

that can be said of almost any useful compound in amateur chemistry =D

Eddygp - 19-11-2012 at 09:06

Lol

barley81 - 19-11-2012 at 13:28

A common test is to hold a stirring rod with a drop of dilute KMnO4 solution over the vessel. If there is SO2, the drop will become colorless.