Copper Detective Lab
The purpose of this lab is to determine whether the copper in a sample of copper oxide is
copper I (and therefore Cu2O) or copper II (and therefore CuO). The sample of copper oxide is
dissolved in HCl forming a solution of copper (I or II) chloride. The resulting solution is reacted
with metallic aluminum to precipitate solid copper. When the copper is dried, the mass is
determined, and the chemical formula of the original copper oxide can be determined. The
possible reactions for the lab are:
Cu2O + 2HCl  2CuCl + H2O
3CuCl + Al  AlCl3 + 3Cu
or
CuO + 2HCl  CuCl2 + HCl
3CuCl2 + 2Al  2AlCl3 + 3Cu
Procedure:
1. Mass a clean and dry 50 mL beaker and record the value. Leaving the beaker on the
balance, zero it out and add approximately 0.25 g of the unknown copper oxide to the
beaker. Record the exact mass of the unknown copper oxide.
2. Use a pipette to add 2.5 mL of 6M HCl to a 10 mL graduated cylinder. Add the 6M HCl
solution to the beaker and gently swirl the beaker until all of the copper oxide dissolves to
form the solution of copper (I or II) chloride.
3. While waiting for the copper oxide to dissolve, cut a 40 cm long piece of aluminum wire.
Use a piece of sandpaper (and a paper towel to protect the table) to remove the aluminum
oxide coating. Wipe the wire with a paper towel and wrap it into a loose coil (see the
instructor’s demo coil).
4. When the copper oxide has been completely dissolved, add about 10 mL of distilled
water to the beaker and swirl to mix. Once the dilution is complete, add the coil of
aluminum wire to the beaker. Observe the reaction that takes place between the
dissolved copper ions and the metallic aluminum.
5. When the reaction is complete (blue color goes away, no more bubbles), carefully
decant/pour the reaction mixture down the sink making sure that the copper coated coil
stays in the beaker and that no copper is lost.
6. Separating the copper: Use distilled water from the wash bottles, tweezers, and a stir rod
to separate the copper from the aluminum wire (you might not be able to get absolutely
all of it). Let the copper stay in the beaker and remove the aluminum wire. Return the
aluminum wire to the designated spot. Turn a hot plate on low in preparation for step 9.
7. Washing the copper with water: Add several mLs of distilled water (it doesn’t matter
exactly how much) to the beaker. Decant/pour off most of the water down the sink
(without losing any copper) and then use a pipette to remove the last of the liquid.
Repeat with more distilled water.
8. Washing the copper with acetone: Add several mLs of acetone (it doesn’t matter exactly
how much) to the beaker. Decant/pour off most of the acetone down the sink (without
losing any copper) and then use a pipette to remove the last of the liquid. Repeat with
more acetone.
9. Carefully heat the beaker on the hot plate to boil off most of the acetone. When the
visible liquid is gone, remove the beaker from the hot plate.
10. Mass the COOLED beaker with the copper and record the value. Then wipe the beaker
with a paper towel place the copper in the trash (make sure the beaker is clean before
returning it to the counter).
11. Clean up!
To earn all points: you must focus so you can do this lab in ONE period!
Calculations, SHOW ALL FORMULAS used and one example of each calculation.
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Determine the mass of the copper recovered. Indicate how this could be done
Use the mass of your original unknown copper oxide and the mass of copper recovered
to calculate the mass % of copper in the oxide.
Calculate the mass % of Cu in CuO and Cu2O. Compare your results with the mass % of
copper from your unknown. What is the formula of the copper oxide?
Write a conclusion that summarizes your results, and gives an analysis of sources of the
error in your data. You should think through the procedure step-by-step to determine
where and how errors might have been introduced. What could you have done to
minimize each of these errors?