Description of experiment
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Needed compounds:
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acetone : CH3 CO CH3
sulphuric acid : H2SO4
anhydrous chromic acid : CrO3
Class:
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elem=C,Cr
redox
Summary:
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Chromium trioxide dissolves well in acetone, but it does not react. When
sulphuric acid is added, then it does react and it can do so nearly
explosively!
Description:
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Add some solid CrO3 to a few ml of acetone in a test tube: The solid dissolves
and a clear brown liquid is obtained. The color of the solution is very dark.
Add a few drops of sulphuric acid and swirl the test tube: The acid mixes with
the liquid, the liquid becomes somewhat darker. Some heat is produced, the
liquid becomes luke-warm (30 C or so).
Add a few more drops of acid, but do not swirl now: The acid sinks to the
bottom. Along the path, where the acid flows along the glass wall, a green band
can be observed, which sticks to the glass.
After a few seconds, it looked as if the liquid became viscous and the color
shifted to dark green and turbid. At a certain moment there was a soft POP
noise and the contents of the test tube was gone! All of it was blown out of
the test tube and the experiment caused a real mess of dark green turbid
splashes all around the working place! The test tube was not hot after the
reaction, it was warm though.