Electrolytic Cells

Here, we show the laboratory preparation for 10 students working in pairs, with some excess. Please adjust quantities as needed.

• Put on a lab coat, splash-proof safety glasses, and nitrile gloves. You'll prepare a concentrated solution of copper sulfate in sulfuric acid, which must be prepared in a fume hood. Be sure to keep plenty of baking soda available in order to neutralize spills.
• Make 6 L of copper sulfate in sulfuric acid solution. Place a large magnetic stir bar inside a 6-L Erlenmeyer flask. Set the flask on the stir plate, but don't turn on the stir setting yet.
• Carefully, pour approximately 250 mL of sulfuric acid into a 400-mL beaker.
• Use a graduated cylinder to measure 250 mL of sulfuric acid and transfer it to the flask.
• Measure 5 L of very hot tap water and transfer it to the flask as well. Be aware that the solution will get very hot.
• Turn on the stir setting and let the solution mix.
• Weigh 2.2 kg of copper sulfate and add it incrementally to the flask, allowing each addition to dissolve before adding the next.
• Once the copper sulfate has dissolved, add another liter of hot tap water to the flask.
• As the solution is stirring, obtain a 10-L carboy and label it as 'Concentrated CuSO₄’.
• Carefully transfer the homogeneous solution from the flask into the carboy. Rinse the flask with 2 more liters of hot water and pour the solution into the carboy.
• Store the capped carboy in a corrosives cabinet until you are ready to begin the lab.
• Each group will need 50 mL of acetone, so be sure to have enough for all groups. Note: Acetone is highly flammable; therefore, it should be stored in a flammables cabinet until the lab class.
• Each group will need a 1 x 9 cm strip of copper sheet. The copper sheet is already pre-cut, so count out the number of strips needed--one for each group.
• Obtain a roll of 18-gauge copper wire and cut it into 3-in long pieces. Each group will need one piece, so cut as many as is needed.
• Cut a sheet of emery paper into 1 by 2-inch pieces. Each group will also need one 10-ohm resistor, so set out a container of those in a common area along with the copper sheet, copper wire, and emery paper.
• Provide a labeled 20-L container in the hood for organic waste.
• Set out the following equipment and glassware at each lab station (suggested that students work in pairs):

  1    Stir plate

  2    Disposable pipettes

  1    Stir bar

  1    Current probe and data acquisition system

  1    Flash drive

  2    50-mL beaker

  1    250-mL beaker

  1    Watch glass

  1    1.5-V battery

  3    Electrical wires with alligator clips

  1    Brass key