Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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dimethylamine borane : (CH3)2NH.BH3
hydrochloric acid : HCl
vanadyl sulfate : VOSO4.5H2O
Class:
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elem=V,B
redox
Summary:
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Vanadyl ion is not reduced by borane to vanadium in a lower oxidation state.
Description:
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Add a solution of vanadyl sulfate to an excess amount of a solution of
dimethylamine borane: A grey/green precipitate is formed. This precipitate
is formed at once.
Add some hydrochloric acid: The precipitate quickly dissolves, the solution
becomes sky-blue, and quite some gas is produced. When the liquid is not
shaken, then hardly any gas is produced, but on shaking, the liquid is
bubbling fairly vigorously. The gas can easily be ignited and then it either
burns with a popping noise, or it makes a whistling noise. The gas is
hydrogen.
Although quite a lot of hydrogen was produced, the color of the solution
remained sky blue. So, the hydrogen is not capable of reducing the vanadium.
Remark: This experiment was performed to check whether the dimethylamine
borane complex is capable of reducing vanadium to its +3 oxidation state,
but this is not the case. Reducing vanadium to its +3 oxidation state (or
even all the way down to +2) can only be achieved with zinc metal.