Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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chromium (III) chloride hexahydrate : CrCl3.6H2O
cupric chloride dihydrate : CuCl2 . 2H2O
Class:
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elem=Cr,Cu
coordination
Summary:
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Chromium (III) chloride hexahydrate cannot be dehydrated by simple heating.
Copper (II) chloride dihydrate can perfectly be made anhydrous.
Description:
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Sequence 1:
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Put some copper (II) chloride dihydrate in a heat resistant glass beaker and
heat carefully over a flame: The solid changes color from cyan to green/yellow.
On further heating, it becomes dark brown. Quite some water is released, which
condenses on the glass walls higher up in the beaker. No smell can be observed,
so what is released indeed is (almost) pure water. Finally, a perfectly dry
dark brown solid remains.
Let cool down and add a small amount of water to the dark brown solid: The
solid turns green at once and fairly quickly all of it dissolves and a clear
and green solution is obtained.
Add much more water: A clear pale blue liquid is obtained.
Sequence 2:
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Put some solid dark green chromium (III) chloride hexahydrate in a heat
resistant dry glass beaker and heat carefully over a flame: The solid melts and
a dark green/brown liquid is obtained. On further heating, a thick choking fume
of wet HCl is produced and the melt bubbles. So, the salt looses water and HCl.
At this point heating is stopped.
Let cool down: The molten chromium (III) chloride does not solidify, a thick
almost black syrup remains.
Add a lot of water: The syrup quickly dissolves and a green and clear liquid is
obtained.