Microscale Chemistry Experimentation for Teachers
8. Electrochemical reactions of salt water using a carbon anode:
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8. Electrochemical reactions of salt water using a carbon anode:
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A
previous
experiment is repeated by replacing replacing one of the iron electrodes
by writing lead used as carbon anode.
Left:
Salt water in a small plastic container is electrolyzed by 4.5 V between
the Fe cathode (-) and the C anode (+).
Close
to the anode a tissue paper wetted by potassium iodide solution is placed
on the container.
A
brownish colour appears showing that Cl2 was formed. It transformed
I- into I2.
Middle:
After that a tissue paper wetted with conc. ammonia solution is placed
on the container.
A
white fume proves that HCl gas was also formed reacting with ammonia gas
leaving ammonium chloride.
Right:
Looking closer to the electrodes you can observe gas bubbles at anode and
cathode.
Explanation
of the cathode reaction: 2 H2O + 2e- -------red---->
2 OH-(aq) + H2 (g)
Explanation
of the anode reaction:
2 Cl- ----------ox----> Cl2 (g) + 2e-
Explanation
of the HCl formation:
H2
(g) + Cl2 (g) --> 2 HCl (g)