Description of experiment
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Needed compounds:
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sulphuric acid : H2SO4
cupric chloride dihydrate : CuCl2 . 2H2O
Class:
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elem=Cu
coordination
Summary:
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Cupric chloride dihydrate is dehydrated by concentrated sulphuric acid.
Description:
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Add a few drops of concentrated H2SO4 (96%) to blue/green cupric chloride
dihydrate: As soon as the acid touches the cupric chloride, the compound
turns brown (the color of anhydrous cupric chloride). No gas is evolved.
The latter is a remarkable difference with e.g. NaCl, which produces HCl-gas,
when treated with concentrated H2SO4.
Quickly add a large amount of water: The acid and the brown solid dissolve.
Around the brown solid, the liquid becomes green, but when everything is
dissolved, the liquid becomes light blue.
BEWARE: Only use a very small amount of H2SO4, relative to the amount of
water and add the water to the acid at once!