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A-8
Once all of the acid has passed through the filter paper, rinse the filter paper with a few millilitres of
deionized water (maximum of 2 to 3 mL) and let this drain into the beaker as well. As the copper(II)
carbonate reacts, a colorless gas will form. Add another 3 mL of 6.0 M H2SO
4
directly to the CuSO
4
solution, and then heat the solution to ensure that all of the CuCO3 dissolves.
NOTE: All of the CuCO3 must be reacted at this point. If the precipitate has not completely
reacted, consult your laboratory instructor.
The resulting heated copper(II) sulfate solution will be filtered using the “gravity filtration” technique to
remove any insoluble impurities that might interfere with crystal formation. To do this, place a folded piece
of 11.0 cm filter paper in a glass funnel then insert the funnel in an iron ring which has been clamped to a
retort stand. Label a 50 mL beaker with your name and laboratory section. Place the beaker under the
funnel with the funnel positioned so that the solution will drip into your labeled 50 mL beaker. Pour the
CuSO
4
solution into the funnel and allow it to drain through the filter paper into the labeled 50 mL beaker.
Wash the filter paper with ~ 2 mL of deionized water to transfer all of the copper(II) sulfate solution to the
beaker.
In order to concentrate the solution so that the CuSO
4
will crystallize, heat the solution to a gentle boil in an
uncovered beaker. Allow the excess water to evaporate until the volume of the solution is ~12-18 mL.
Remove the beaker from the hot plate and allow the solution to cool for 3-4 minutes. Give the beaker to
your laboratory instructor. Your solution will be stored in a secure cabinet and returned to you at the
beginning of the next laboratory period. Over the week, copper(II) sulfate crystals should form in solution.
Part IV. Copper(II) Sulfate Crystals.
Next week, your graded copper(II) sulfate crystals will be returned to you to be used in Experiment B. If
the solution is green there is too much Na2CO3 and not enough CuSO
4
. This will occur if insufficient time
is allotted for the complete precipitation of the CuCO3 in Part II or if the CuCO3 is not adequately washed
with deionized water.
Before leaving the laboratory, check to make sure that all of your equipment is clean, and back in your
drawer. As well, all communal equipment must be cleaned and returned to the designated location in the
laboratory.
