[juggler33]

Hi,

I am writing a lab report for a copper silver nitrate reaction and I need a little help...

The equation is 1Cu + 2AgNO3 -> 1Cu(NO3)2 + 2Ag

We had a test tube of 50ml (0.38 M) silver nitrate, we placed a length a copper wire in, and silver crystals started forming very quickly on the copper wire. At first they were a light gray, then they turned blue (due to the Cu being released into the solution) but then they turned brown and then black (after about 15 min) I can't explain this phenomenon, any ideas?

Also after about 15 min of the copper being submerged in the solution, I noticed a "band" of clear solution near the bottom of the test tube (by that time everything was very blue except for this small band of clear solution about 1cm from the bottom of the test tube). My second question is, why does this happen? The one idea I have is if this is an exothermic reaction, that could create convection currents that might carry the ionic Cu to the bottom of the tube first insted of letting it just naturally dissipate (the next time I saw the test tube was 24 hours later and the band had disappeared).

Thanks in advance!