wat07 Ammonia gas absorbed
by generating a fountain
Sodium
hydroxide is very corrosive:TEACHER EXPERIMENT
* Ammonia gas [NH3(g)]
is produced like in the previous experiment.
* Left photo: This
time pass the gas into an empty vial through the transfusion tubing.
* This vial is closed by
a stopper which is in contact not only with the tubing.
* (The stopper also
contains a short hypodermic needle: The air in the vial can
be pressed out through this needle by the incoming NH3 gas).
* As soon as ammonia appears
at the plastic end of the needle replace the stopper by a second
one.
* Pierce this stopper
by a long injection needle (without
tip)
only 0.5 cm deep.
* Middle: Turn this
vial full of NH3 gas upwards down, dip the plastic end of its
needle into a second vial full of water containing a drop of UI. Wait.
Observation
Right:
After
some minutes a fountain starts transporting water into the upper vial.
The upper vial has a lilac colour.
Explanations:
In the first step ammonia gas (NH3) replaced all
the air in the vial.
This gas dissolves extremely
well in water: All the NH3 gas was was taken up by the
first microdrop of water reaching the tip of the needle. This resulted
is a negative pressure which powered the fountain.
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published: 26.10.2001 ...............................last
modification: 08.05.2010