Growing tin dendrites
A single displacement reaction (as in case of tin hedgehog or silver fur) is not the only method to throw out a metal of its solution. Electrolysis is another one. When current flows through a solution, the electrons connect to the ions and reduce them to a metal.
In case of tin (II) chloride you can see the metallic tin disposing on a cathode. Tin ions are reduced to the metallic tin and form dendrite like crystals. The metal of anode is loosing its electrons, turns into ions and “dissolves”. The growth of tin dendrites is a beautiful process to observe.
For this experiment I followed the instruction from the MEL science webpage and used the supplies from the “Tin” set. Please, visit their page for more information and a detailed instruction video.
As you can see, I have performed this experiment twice (the first video was not sharp enough as you may have noticed). For the second time I used paperclips as electrodes to prevent the dissolving of a crocodile clip.
The chemistry of this process is already described in details on the MEL Science page shown above. Shortly:
Cathode-: 2Sn2+(solution) + 4e-→ 2Sn(solid)
Anode+: 2H2O – 4e- → O2 + 4H+
And a secondary reaction: 2SnCl2 + O2 + 2H2O → 2SnO2 + 4HCl