[Firam]

I read popular science and it showed how HCl and Zn react and how this can be used to isolate copper in a penny. So I tried this and got some good results. A final penny was left and I decided to cover it with the top of the petri dish. This morning it is green. I wonder what I made. The reaction only requires HCl + Zn = H2 + ZnCl. There is no oxygen or air in the equation. I also thought that hydrogen is colorless. My only idea is that I formed chlorine gas somehow, it that is true I need to be careful. But I should be ok with a wet rag over my mouth and gloves when I open it. What else could it be?

 

[Binaural Fusion]

Copper rusts green.

 

[ex0du5]

Yep probably just oxidation on the copper....my chemistry skills are rusty though (pun intended).

 

[Firam]

That would turn the whole dish green from one penny? But doesn't oxidation require oxygen, which I have cut off? I see here:

http://jchemed.chem.wisc.edu/JCESoft...OXCU/PAGE1.HTM

That 2 Cu(s ) + O2(g ) --> 2 CuO(s ) . In fact CuO(s ) + H2(g ) --> Cu(s ) + H2O(g ) . So my abundent hydrogen would actually reduce the effect.

 

[65535]

The reaction should go 2HCl + 2Zn = H2 + 2ZnCl

The zinc in the penny reacts with the HCl to produce Hydrogen Gas and Zinc Chloride. The copper should be left shinny in the bottom. Although I'm not entirely sure that the reaction would go well seeing as the copper is coating the Zinc. When you put it in did any sign of reaction take place such as bubbling or heating? I have never seen HCl turn copper green, actually normally it eats it, leaving you with corroded yet orange copper.

 

[Binaural Fusion]

Some oxidizing agent (doesn't need to be oxygen, Cl and O are your primary culprits) came in in the night and oxidized your copper. Since it is green it sounds like some of the Cl- in the acid got in there and started wreaking havoc. No worries though, you need to do some fun electrochemistry to get much Cl2 out of your mix. BTW you'd see the same green oxidation if you put the a shiny penny in some brine.

I had put CLR (Muriatic Acid) on some pennies a while ago and the exact same thing happened even though I had rinsed all the acid off the pennies. The all oxidized brownish black overnight (Oxygen's handiwork)

 

[Firam]

Quote:

Originally Posted by Binaural Fusion /img/forum/go_quote.gif I had put CLR (Muriatic Acid) on some pennies a while ago and the exact same thing happened even though I had rinsed all the acid off the pennies. The all oxidized brownish black overnight (Oxygen's handiwork)

Yea that was what I was doing. Filed the edge off the penny and put them in some muriatic acid. It bubbled for a while and left just the copper.

All of them that were open to the air turned out well. The one which I put the cover on the whole dish turned green. I don't know how the penny has faired though, I can't see it. I watch too much TV that color of green normally means poison, the dish looks like the VX in The Rock, or Chimera in MI2.

 

[Sh0eBoX]

while we're on the subject of chemistry... anyone care to try this?

http://www.metacafe.com/watch/601280...stant_hot_ice/

looks so awesome

 

[Firam]

Got the courage to open it. It seemed harmless, no smell or anything. Wouldn't drink it but no as bad as I feared. Just the lime green liquid in the bottom and no penny! It has been 36 hours but I believe the penny was gone after 12. Other pennies survived 12 hours. Can't say what happened except that a build up of hydrogen made some sort of change in the system leading to the dissolving of the penny. Even if I don't know why, it was very interesting.

 

[Zorander]

You won't get pure copper with that method. Electroplating is the way to go, but probably too expensive for the average DIYer.