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B-6
stir rod
to dislodge the copper metal and expose the zinc metal surface or wash the copper off the zinc
metal using a fast stream of water from a wash bottle.
NOTE: If the solution is not colorless after all of the zinc has reacted, see your laboratory instructor.
D. Recovery of the copper metal.
Remove any unreacted zinc metal from the reaction solution and then add 2 mL of
6.0 M H2SO
4
and 5 mL of deionized water to the evaporating dish. Allow this solution to stand for
5 minutes during which time you can set up a vacuum filtration system similar to the one used in
Experiment A-Part II substituting a tiny Hirsch funnel for the Buchner funnel. Be sure to wet the
filterpaper prior to using the funnel during the filtration procedure.
All of the zinc should have reacted with the H2SO
4
. Once gas evolution has stopped, isolation of the
copper metal can begin. Carefully decant the liquid off the copper metal into a waste beaker. Wash the
copper metal in the evapourating dish three times with ~10 mL of deionized water, gently stir tthe
copper/water mixture with a plastic stir rod each time and decanting each 10 mL portion into the waste
beaker. Attach your system to house vacuum making sure that you have placed a dampened filter paper
in the Hirsch funnel. Using a gentle stream of water from your dionized water washbottle, gently dislodge
the copper metal from the evaporating dish onto the center of the filter paper in the Hirsch funnel. Use
the plastic stir rod to push the metal onto the filter paper if necessary. Use deionized water to remove all
of the copper metal from the evaporating dish.
When all of the liquid has drained through the filter paper, wash the copper metal with 20 to 25 mL of
acetone, again, squeezed from a wash bottle. If the copper metal is dark brown, rewash it with HCl, then
water, and finally acetone. Air-dry the metallic copper by continuing to apply a dynamic vacuum for at
least 10 minutes. The product should be bright reddish brown like a new penny. If necessary, dry the
copper metal between two pieces of filter paper. Press the papers together firmly so that the paper
absorbs any residual acetone.
Accurately weigh a vial on an analytical balance. Quantitatively, transfer the copper metal to the vial
using the funnels available on the instructor’s bench and re-weigh the copper metal and vial. Determine
the mass of the copper metal recovered. Label the vial with your name, the mass of copper metal and
the percent yield of copper metal, and turn it in to your laboratory instructor for grading.
