Description of experiment
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Needed compounds:
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sulphuric acid : H2SO4
potassium dichromate : K2Cr2O7
sodium chloride : NaCl
Class:
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elem=Cr
acid/base
Summary:
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Hexavalent chrome forms a stable volatile compound, when mixed with chloride
in strongly dehydrating conditions. The compound formed is called chromyl
chloride and its constitution is CrO2Cl2.
Description:
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Mix some table salt with finely powdered potassium dichromate (appr. 1 part of
salt, mixed with 2 parts of K2Cr2O7) and add some concentrated H2SO4 (appr.
96 %): The liquid becomes red and starts foaming. A colorless gas is formed,
which fumes on contact with air (HCl) and a brown/red vapor is formed, which
escapes from the red liquid. This brown red vapor is the volatile compound
chromyl chloride.
Add some ligroin: The red compound partly dissolves in the ligroin, but most
of it remains in the acid layer. The brown/red vapour dissolves in the
ligroin. After adding the ligroin, no other smell than the smell of ligroin
could be observed.