Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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hydrochloric acid : HCl
phosphorus red : P
vanadium pentoxide : V2O5
Class:
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elem=P,V
redox
Summary:
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Vanadium pentoxide does not seem to react with red phosphorus.
Description:
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Mix some finely powdered red phosphorus with finely powdered vanadium
pentoxide. Take a small amount of the resulting powder and keep in a flame: The
red phosphorus starts burning with a small orange flame and a lot of white
smoke of P4O10. No strong redox reaction seems to occur between the V2O5 and
the red P.
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Put some of the powdered mix in a test tube, which is flooded with CO2-gas in
order to remove any oxygen in the test tube.
Heat the test tube in a flame: The red phosphorus decomposes and evaporates.
White phosphorus is deposited on the glass wall of the test tube. The
powder-mix turns black. There is no visible reaction between the red phosphorus
and the vanadium pentoxide.
Let the test tube cool down and then add some hydrochloric acid: Part of the
black powder dissolves. A very dark green solution is obtained, which is very
turbid. Apparently most of the solid does not dissolve easily in the acid, and
remains of unreacted red phosphorus may also float around in the liquid.
The white phosphorus at the walls of the test tube starts smoking as soon as it
comes in contact with fresh air.