The Chemistry of Copper Electrolysis Objectives Apply basic
The Chemistry of Copper Electrolysis Objectives Apply basic chemistry principles to understand the process of electrolysis Understand how electrolysis is used in the processing of copper ores
Electrolysis Uses an electrical current to move ions in an electrolyte solution between two electrodes In copper electrolysis, when current is applied, copper ions (Cu2+ cations) leave the anode (+electrode) and move toward the cathode
(electrode) - + Cu2+ Anod e (impu r e coppe r)
CuSO4 Solution Catho de (pure coppe r) Lab-scale Electrolysis In this experiment, a penny will be used as the copper source/anode, and a dime will be used as
the cathode They will be placed in an electrolyte solution A current will be supplied by a 9V Hypothesis What do you think will happen in this experiment? Write a hypothesis on worksheet
Materials Dont forget safety goggles and Protocol Clean a pre1982 penny with salt/vinegar mixture, rinse with water and allow to dry
Protocol Cut a 33 cm length of 18gauge copper wire Peel apart to separate redand blackcoated wires 33c m Protocol Use 1.6 mm gauge
setting on wire stripper to remove ~1.5 cm length of rubber coating from both ends of each wire to expose the copper filaments, being careful not to sever copper Protocol Twist filaments together tightly
and fold A B C A) Exposed copper filaments; B) twisted copper filaments; and C) final product of twisted and folded copper filaments. Protocol Make two holes in the cardboard
an inch apart Push the red wire through one hole and the black wire through the other Protocol Insert each folded end of wire into handle of matching alligator clip so that wire
touches metal inside the clip handle red wire should have a red alligator clip at each end; black wire should have A B A) Unattached copper wires; B) copper wires attached to alligator clips.
Protocol Clip the penny into the red electrode and clip the dime into the black electrode Complete wire assembly: red and black wires pushed through cardboard with alligator clips attached and coins inserted. Protocol OPTIONAL step to be completed
before inserting wires into cardboard: Weigh each coin/copper wire assembly separately and record the mass Penny/red wire/red clips Dime/black wire/black clips Protocol Pour 200 mL of the copper sulfate electrolyte
solution into the beaker Place the wire assembly over the beaker so that the coin "electrodes" are Note: the two electrode assemblies must not touch one another. Protocol Clip each
connecting wire to the 9V battery: Clip red to positive terminal Clip black to negative Protocol Allow the
electrolytic cell to operate for 30-60 minutes OPTIONAL: Record the length of time the cell was operating Protocol Carefully remove wire assemblies
and hang in an empty beaker until dry (5-10 min), being careful not to touch coins, so as not to lose any of the copper plating Protocol Examine the coins for changes
OPTIONAL: Weigh each coin/copper wire assembly and record the mass. Calculate the difference in Lab Results Initial mass of penny [g] Final mass of penny [g] Difference in
mass [g] Initial mass of dime [g] Final mass of dime [g] Difference in mass [g] Lab Results (Example) Initial mass 4.764 of penny [g] Final mass 4.371
of penny [g] Difference in -0.393 mass [g] Initial mass 3.549 of dime [g] Final mass 3.988 of dime [g] Difference +0.4 in mass [g] 39 Electrolysis Explained Coating
the dime with copper from a penny When electrical current is applied to the penny (anode), copper cations are set free in the electrolyte solution. Cu2+ ions in solution are attracted to the dime (cathode). Anode Positive Electrode Cu (solid) Cu2+(aqueous) + 2 e-
Cathode Negative Electrode Cu2+(aqueous) + 2 e- Cu(solid) Real-Life Copper Electrolysis Anode slabs of impure copper are hung in a large tank Act as positive electrodes Thin
starter sheets of pure copper (15 lb) are hung in between anodes Act as cathodes/negative electrodes Tank is filled with electrolyte solution Copper sulfate and sulfuric acid Electric current is applied (over 200 amperes) Real-Life Copper Electrolysis Positively-charged copper ions (cations) leave the anode (positive electrode) Cations move through the electrolyte
solution and are plated on the cathode (negative electrode) Real-Life Copper Electrolysis Other metals and impurities also leave the anodes Drop to the bottom of the tank or stay in solution Can be collected and refined to recover other valuable metals such as silver and
gold After 1-2 weeks of electrolysis, the final products are copper cathodes Weigh 375 pounds Questions At the end of the experiment, the dime should be coated with copper. What are the possible sources of this coating? How could you determine which sources contributed to the coating,
and how much? Why do you think copper wire is used for the wire assemblies? What differences would you expect if the electrolytic experiment were allowed to run for a short time versus a long time? Questions What
would you expect to see if you made the dime the anode and the penny the cathode, and/or used different coins in the experiment? Would you need to change anything else? To reach commercial scale, how do you think you would need to change the materials from this small experiment to make a 375-pound copper cathode?
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