Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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sulphuric acid : H2SO4
acetone : CH3 CO CH3
sodium hydroxide : NaOH
sulphur : S8
Class:
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elem=S,C
redox
Summary:
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Sulphur dissolves in hot solutions of sodium hydroxide and disproportionates
in a way, similar to disproportionating of halogens.
When acetone is added, a peculiar blue/green compound is formed in the
acetone. What is this compound?
Description:
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Add some sulphur to a concentrated solution of sodium hydroxide: The sulphur
does not react. Part of the sulphur floats on the liquid, larger particles
go to the bottom.
Heat the liquid and boil gently for a while: The sulphur dissolves. The liquid
becomes intense yellow, when all sulphur is dissolved it is intense brown/
yellow.
Add some acetone: The acetone does not mix completely with the liquid. On top
of the aqueous layer an acetone layer is formed. Both layers become turbid,
due to small droplets of the one liquid, finely dispersed in the other liquid.
The aqueous layer remains yellow/brown, the acetone layer becomes blue/green.
Add a large amount of water: All acetone dissolves, the liquid becomes clear
and yellow.
Add a small amount of sulphuric acid (still an excess amount of NaOH is left):
Where the acid mixes with the liquid a cloud of yellow precipitate is formed,
before it is neutralized by the hydroxide. When the entire liquid is shaken,
it becomes turbid. No smell of sulphur dioxide or hydrogen sulfide is
observed.