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02  Direct electron transfer from metals to copper ions
This experiments is a model of removing cleaning waste water from contamination by copper salts.
Material
Magnifying glass, microscope, slide, 3 ampoules (5 mL, high) in stands (stoppers of infusion bottles), scissors, nail, copper and aluminium wire (alternative: Al kitchen foil or closure of a softdrink can), diluted copper(II) sulfate solution.
Experiment 
1. Transfer a nail, a copper wire and an alumium wire in an ampoule half full with copper salt solution.
2. Wait until the colour has disappeared (Photo 1).
3. Place a drop of copper(II) sulfate solution on a slide.
4. Observe what happens under the microscope while you push a piece of aluminium into the center of the drop.
5. Wash with water, leave it for drying and carefully remove the metal from the slide.
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Observation
a) Small branches with the colour of copper grow from the aluminium piece (Photo 2 - 4).
b) Gas bubbles.
Explanation 
a) The copper(II) ions [Cu2+(aq)] remove electrons from the metals (Al, Fe). The copper ions are reduced while the metals are oxidized
                reduction:          3 Cu2+(aq) +  6e- --> 3 Cu(s)
                 oxidation:                        2 Al(s) --> 2 Al3+(aq) + 6e-
       Redoxreaction:        3 Cu2+(aq) + 2 Al(s) -->  3 Cu(s) +  2 Al3+(aq)
   Total reaction:        3 CuSO4 (aq)  + 2 Al(s) -->  Al2(SO4)3(aq) +  3 Cu(s)
 
b) The copper(II) ions [Cu2+(aq)]  are acids. This means that electrons are not only transfered from aluminium to copper(II) ions but also to H+(aq).
                                               Al(s) + 3 H+(aq) --> Al3+(aq) + 3/2 H2 (aq)
In the following experiment you will measure the loss of weight during electron transfer from Al metal to copper ions.                                                                           
back....... go on...............first published: 25.10.2001................................................last modification: 12.06.2008