Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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sulphuric acid : H2SO4
methanol : CH3OH
ammonium thiocyanate : NH4SCN
potassium chromate : K2CrO4
potassium dichromate : K2Cr2O7
Class:
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elem=Cr
redox
Summary:
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Potassium dichromate dissolves in methanol, albeit not as well as in water.
Potassium chromate hardly dissolves in methanol. When ammonium thiocyanate
is added, then the liquid becomes deep yellow. Is this due to chromate, or
is this some reaction product from the thiocyanate?
Description:
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Sequence 1:
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Add some potassium dichromate to some methanol: Part of the solid dissolves.
The liquid becomes light orange/yellow.
Add some concentrated H2SO4 (96%): A violent reaction occurs. The liquid
becomes green and starts boiling (probably reaction between CH3OH and H2SO4).
Sequence 2:
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Add some potassium chromate to some methanol: The liquid becomes very pale
yellow, almost colorless. Only if one compares the liquid with another true
colorless liquid, one can tell that it is yellow.
Add an excess amount of NH4SCN: The solid quickly dissolves and the liquid
slowly turns more yellow. After several minutes, the liquid is deep yellow
and clear. At the bottom there still is almost all of the undissolved solid
potassium chromate.
Add some concentrated H2SO4 (96%): A violent reaction occurs, the liquid
becomes grey/purple and very turbid.
Add a lot of water: The liquid is grey/violet and turbid.