Does urea decompose to CO2 and NH3 under acidic conditions?
Only when boiled down to high concentrations and a very high temperature as per the link provided by idrbur.
I suspect your cold pack is not urea based but that it contained a nitrate salt (probably NH4NO3), hence you effectively prepared a dilute
solution of nitric acid when adding sulfuric acid and so this would happily oxidise the copper producing lots of nitric oxide or nitrogen dioxide
(brown gas and toxic) depending on the concentration of the acid. If your solution turned to a very deep blue, then it was probably specifically
ammonium nitrate as the tetraamminecopper(II) complexes have a very intense deep blue colour.
If it formed a precipitate coloured blue by the copper, then it might have been calcium nitrate (thus forming gypsum).
[Edited on 8-7-2015 by deltaH]vmelkon - 8-7-2015 at 10:56
OK, that was a weird thread.
I had done copper + H2SO4 + NH4NO3 before. The solution does go blue but it isn't an intense blue so I don't think tetraminecopper(II) forms under
acidic conditions.
This one was weird since it was at first clear. Bubbles come off the copper but the glass walls are bubbly as well. Shaking it makes it go white since
millions of microscopic bubbles are formed in the liquid. They quickly rise and pop.
The solution did eventually go blue but it isn't intense with respect to the amount of the unknown salt from the cold pack that I added.
I'm doing another test: 3 M H2SO4 + the unknown salt.
//UPDATE:
I think the salt in the cold pack is indeed NH4NO3.
Nothing happens when I add just H2SO4.
I dropped a piece of copper wire and immediately had bubbles on it.
The thing I noticed is that as the bubbles rise, they get smaller. So, that is why when I shake it, it effervesces.
And finally, I smelled it and it does smell like NO2.
[Edited on 8-7-2015 by vmelkon]deltaH - 9-7-2015 at 01:42
