wat06 Ammonia
gas forms an alkaline solution
Sodium
hydroxide is very corrosive:TEACHER EXPERIMENT
* Photo: Put a spatula
of ammonium chloride (NH4Cl) and a tablet of sodium hydroxide
(NaOH) into the left vial.
* Close it by a stopper
which is connected to the mouth of a second vial by a transfusion tubing.
* Threequater fill the second
vial water, add a drop of universal indicator. The tubing ends
above
the liquid. (The vials are also connected by a piece
of wire).
* Heat the vial with ammonium
chloride and sodium hydroxide.
ObservationPhoto:
Starting at the surface the liquid changes its colour from yellow to lilac.
Explanation:
In the left bottle ammonia gas is formed by heating the solids:
NH4Cl(s)
+ NaOH -------heating-------> NH3(g) + NaCl(s)
In the right bottle water and
ammonia gas react leaving an alkaline solution with ammonium (NH4+)
and hydroxide (OH-) ions:
NH3(aq) + H2O(l)
-------transfer of H+ -----> NH4+(aq)
+ OH-(aq)
This is another example
of an acid-base reaction. This time water
is the proton donor.
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modification: 26.10.2001