Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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sulphuric acid : H2SO4
ammonia : NH3
vanadium pentoxide : V2O5
Class:
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elem=V,N
acid/base
Summary:
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Vanadium pentoxide reacts with ammonia, producing a strong hissing noise.
A white compound is created. This probably is ammonium metavanadate,
NH4VO3.
Description:
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Sequence 1:
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Add some ammonia (appr. 25% by weight) to some solid vanadium pentoxide: A
strong hissing noise is produced, as soon as the liquid touches the solid.
The solid becomes off-white/grey (formation of NH4VO3 ?), the liquid becomes
pale yellow. Only a small amount of the solid dissolves.
Sequence 2:
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Add some ammonia (appr. 5% by weight) to some solid vanadium pentoxide: A
faint hissing noise is produced on addition of the liquid. The liquid becomes
intense yellow and a fairly large part of the solid dissolves. With some
heating the remaining solid dissolves and the liquid becomes clear and
colorless.
Let stand overnight: The next morning an off-white layer of crystals has
separated from the liquid and the glass is covered with this compound. These
crystals do not dissolve easily in water. A few times rinsing with water does
not lead to dissappearance of these crystals.
Add some sulphuric acid (1 mol/l) to the wet crystals: The crystals become
yellow/orange. After one minute they are orange/red (they look like solid
potassium ferricyanide). The liquid becomes pale yellow.