. .Work in a hood or outdoor. Use gloves, wear googles. TEACHER EXPERIMENT........
wat04 Hydrogen chloride gas absorbed by water generating a fountain
Experiment
1. Cut off 5 mm of the thick side of the pipette tips and of the hypodermic needles.
2. Pierce the stopper of the 5 ml ampoule and the stopper of the 2 ml ampoule from downside with these pipette tips.
    Cut off 1 cm of the thin ends of the pipette tips.
3. Connect the two pipette tips with the tube.
4. Use the copper wire to make a "test tube holder" for the 5 ml ampoule.
5. Photo 1: Mix a small packet of salt and 10 drops of conc. sulfuric acid inside this 5-ml ampoule.
6. Close it with the first pierced stopper.
7. Pass the gas into the 2-ml ampoule through the tube and the second pierced stopper.
8. Pierce the stopper of this ampoule by a short blunted hypodermic needle: This allows air (Luft) to leave.
9. Heat the mixture in the first ampoule.
10. As soon as white clouds appear at the plastic end of the needle,  replace the stopper by the third one.
11. This stopper is pierced from downside by a long blunted injection needle. Push it in as far as possible.
12. Photo 2, 3: Turn this closed ampoule upside down, dip the plastic end of its needle into an ampoule full of blue indicator solution, wait.
Observations
Photo 2 and 3: Blue solution is vigorously injected into the upper ampoule. (The volume of the fountain was limited by the length of the injection needle).
The colour changes from blue to red.
Explanations

 Hydrogen chloride gas was formed by a chemical reaction between sodium chloride and sulfuric acid:

 H2SO4(l) + 2 NaCl(s) --> Na2SO4(s) + 2 HCl(g)

 Hydrogen chloride gas displaces air in the 2 ml ampoule.

This gas dissolves extremely well  in water producing hydrochloric acid in an exothermic acid-base reaction:

 HCl(g) + H2O --> Cl-  +  H3O+

 The result is decrease of pressure inside the ampoule. The atmospheric pressure causes a fountain effect.

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 back....... go on......first publication: 25.10.2001................................last modification: 26.06.2010 ................................................................................................