Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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sodium metaperiodate : NaIO4
sulphuric acid : H2SO4
vanadyl sulfate : VOSO4.5H2O
Class:
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elem=S,V,I
redox
coordination
Summary:
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When vanadyl sulfate is dehydrated by heating, then the resulting solid only
dissolves partially in water and in dilute acid. When a strong oxidizer is
present, all of the solid dissolves again, forming a soluble vanadium species
in the +5 oxidation state.
Description:
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Heat some solid vanadyl sulfate (hydrated): The solid looses water and a light
blue powdered solid remains. Some white material seems to be present also in
the heated solid.
Add water to the cooled down powdered solid: The solid becomes much darker
blue again and it partially dissolves, giving a blue liquid. After a few days,
there is a clear blue liquid, with a white solid at the bottom.
Add some dilute sulphuric acid to the liquid with the white solid and shake:
The while solid does not dissolve, the liquid remains blue. Even after several
days, the white solid still does not dissolve.
Add an excess amount of solid NaIO4 and shake: The solid dissolves and the
liquid quickly turns orange, due to formation of a condensed vanadium species
in the +5 oxidation state. The white precipitate does not dissolve, so, after
shaking the liquid is turbid. The white precipitate slowly settles at the
bottom again.
Wait a few hours: All solid now has dissolved, so with the addition of the
periodate, which acts as strong oxidizer, all of the white precipitate has
dissolved. The liquid now is totally clear and bright orange.