This demonstration is one of my favorites involving copper chemistry since it is simple, it involves relatively harmless materials and produces a compound whose color differs from the traditional green and blue of copper compounds.
It is based on the fact that, when electrolyzing a concentrated solution of table salt in a divided cell using a copper anode, cuprous chloride is formed in the anolyte and a dilute solution of caustic
soda is produced in the catholyte. By allowing the two liquids to mix, copper (I) hydroxide precipitates
and the table salt is regenerated.
The cell consists of two plastic cups connected by a thin PVC tube. The anode is a copper wire and the cathode a steel plate. The power supply provides 24 volts, the voltage needed to overcome the high electrical resistivity of the cell.
After approximately one hour and twenty minutes of electrolysis, we have enough of the
reagents needed to run the demonstration.
Note the milky appearance of the liquid in the anolyte. This is due to the fact that
cuprous chloride is practically insoluble in water. What we actually have is a suspension,
that is, tiny particles of the compound floating through the liquid.
The liquid in the catholyte also has some whitish material present. This did not happen
in my previous experiments with another brand of salt and I believe that this is due to
calcium and magnesium contaminants precipitating their hydroxides.
If we add an ammonia solution to the cuprous hydroxide suspension, the color changes from bright yellow to blue and the solution loses its opacity. This is due to the formation of the diamine copper complex, which is soluble in water.
Now, if we add a small portion of calcium carbide to the solution, a new color change occurs
and a copper compound with explosive properties precipitates. But that is a topic for another video.
See you there!
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