Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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acetone : CH3 CO CH3
sodium cyanide : NaCN
ammonium thiocyanate : NH4SCN
methanol : CH3OH
copper sulfate penta hydrate : CuSO4 . 5H2O
cupric chloride dihydrate : CuCl2 . 2H2O
Class:
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elem=Cu
coordination
Summary:
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Copper sulfate dissolves in methanol quite well. A blue solution is obtained.
Copper chloride dihydrate also dissolves in methanol quite well. A green
solution is obtained.
With thiocyanate a deep brown complex is formed, which dissolves in
methanol, but at higher concentration this precipitates.
With cyanide, a dirty green compound is formed, which, however, quickly
turns white. This probably is copper (I) cyanide.
Description:
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Sequence 1:
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Add some solid CuCl2.2H2O to methanol and shake: All of the solid dissolves.
The liquid becomes green and clear.
Add some NH4SCN to methanol and shake: All of the solid dissolves.
Add the two solutions to each other: A dark brown complex is formed, which
remains dissolved.
Add a large excess amount of water: The liquid becomes light dirty green and
turbid. In due time it slowly turns lighter. Apparently the copper (II)
compound is reduced slowly to copper (I).
Sequence 2:
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Add some solid CuSO4.5H2O to methanol and shake: All of the solid dissolves.
The liquid becomes blue and clear.
Add a small amount of NH4SCN to the liquid and shake: Around the crystals,
a dark brown compound is formed. On shaking, however, the liquid becomes
turbid and a dirty yellow/green precipitate is formed. The dark brown
compound, formed around the crystals of NH4SCN disappear, when they come
further into the liquid.
Add much more NH4SCN: The liquid now becomes dark brown. Also some dark
brown solid is formed. This solid does not dissolve anymore, apparently
more of the dark brown compound is formed, than can be dissolved in the
methanol.
Add some acetone: The brown solid particles, sticking on the glass now
dissolve and become deep red, like red wine. The liquid becomes deep red
and most of the solid dissolves now.
Pour all liquid into a beaker, filled with water. The deep red compound
disappears, the liquid becomes turbid and light green/blue.
Sequence 3:
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Add some solid CuSO4.5H2O to methanol and shake: All of the solid dissolves.
The liquid becomes blue and clear.
Let liquid stand for a while: The liquid remains blue and clear, but the
glass is covered by a white layer. Whether this is reduced copper (II)
or dehydrated copper sulfate is not clear. More research is needed for
that.
Add some solid NaCN: The liquid becomes turbid and dirty green/brown. Slowly,
however, the color fades. After a few minutes, the liquid is turbid and
white. All copper (II) is reduced to copper (I) and the white solid probably
is copper (I) cyanide.