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P-3
If you are unable to get sufficient current flow, it might be due to one of the factors described above. Points 1
and 2 suggest that you should get as much of the copper wire into solution as you can. Point 3 recommends
that you should try to get the copper wire near the buret (within about 2 cm), and that the exposed nichrome
wire should not be positioned too far up into the buret.
As the oxidation of the copper wire proceeds, the concentration of Cu
2+
ions in solution increases. Because
of this, you must always start each run with a freshly prepared sulfuric acid solution. If this is not done, the
Cu
2+
(aq)
, will be reduced in preference to the H
+
(aq)
and the volume of H
2(g)
collected will be erroneously low.
The method for calculating the amount of hydrogen formed is exactly the same as the calculation of the amount
of nitrogen formed in Experiment D of the Chemistry 101/103 Laboratory Manual. Review this procedure
prior to beginning this experiment. Please contact your laboratory instructor if this information is not available
to you. Remember that your recorded observations should reflect the precision of your measurements.
Record the time in minutes and seconds.
In Part II of this experiment, you will examine a number of simple oxidation-reduction reactions. By
comparing the results from the various tests, you will be able assess which reactions are nonspontaneous and
which ones are spontaneous.
