Redox Reactions

Source: Smaa Koraym at Johns Hopkins University, MD, USA

1. Preparation of SolutionsExpand

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

   • To set up for this lab experiment, wear the appropriate personal protective equipment, including a lab coat, chemical splash goggles, and gloves. All solutions for this lab must be prepared inside the chemical hood.
   • First, prepare 50 mL of an 8 M solution of nitric acid. Carefully pour approximately 30 mL of the stock 15.7 M nitric acid into a 100-mL beaker.
     Note: This will make it easier to pour the concentrated nitric acid into the graduated cylinder without spilling.
   • Measure 25.5 mL of stock nitric acid using a 50-mL graduated cylinder and transfer it into a 50-mL volumetric flask. Fill the remainder of the volumetric flask with deionized water until it reaches the appropriately marked line.
   • Place a small stir bar in the flask and set the flask on a stir plate. Mix the solution until it appears homogeneous.
   • Label a 150-mL glass bottle with the solution name and concentration. Transfer the nitric acid solution from the volumetric flask to the bottle using a powder funnel.
   • Prepare 150 mL of 3 M NaOH solution. Weigh 18 g of NaOH pellets using a top-loading balance and transfer the NaOH to a 250-mL Erlenmeyer flask.
   • Measure 150 mL of deionized water into the Erlenmeyer flask. Add a magnetic stir bar to the flask and set it on a stir plate.
   • Mix the solution until the pellets dissolve and the solution appears homogeneous. Then, turn off the stir plate.
   • Label a 250-mL polyethylene bottle '3 M NaOH' and carefully pour the solution into the bottle. Cap the bottle and store it appropriately.
   • Prepare 50 mL of 6.05 M hydrochloric acid solution. First, pour ~30 mL of stock 12.1 M hydrochloric acid into a 100-mL beaker. Then, use a 25-mL graduated cylinder to carefully measure 25 mL of the stock hydrochloric acid. Transfer the hydrochloric acid to a 50-mL volumetric flask.
   • Fill the remainder of the volumetric flask with deionized water until it reaches the marked line on the neck of the flask. Place a stir bar in the flask and set the flask on the stir plate.
   • Stir the solution until it appears homogeneous. Then, transfer the solution to the labeled polyethylene bottle, cap it and store until needed.
   • Finally, prepare 50 mL of 5.93 M sulfuric acid solution. Carefully pour ~20 mL of glacial sulfuric acid into a 100-mL beaker. Then, measure 16.5 mL of the sulfuric acid using a 25-mL graduated cylinder and carefully transfer the sulfuric acid to a 50-mL volumetric flask.
   • Fill the remainder of the flask with deionized water until it reaches the full line on the neck of the flask. Place a magnetic stir bar in the flask, set it on the stir plate, and stir the solution until it appears homogeneous.
   • Label a 125-mL polyethylene bottle with the solution name and concentration, and carefully transfer the sulfuric acid from the volumetric flask to the bottle. Cap the bottle and store it for later.
2. Preparation of the LaboratoryExpand
   • Weigh ~5 g of copper shot into a labeled bottle. Place it by the balance with an empty beaker labeled 'excess', additional weighing tins, and spatulas.
   • Obtain granulated zinc and weigh 7 g into a labeled bottle. Place another empty beaker labeled 'excess', weighing tins, and the bottle of zinc by the balance.
   • Set out one bottle containing methanol and several other bottles containing deionized water.
   • Set out the following glassware and equipment at each workstation (we suggest that students work in pairs):

     1    Disposable 1-mL pipette

     1    500-mL filter flask

     1    83-mm Büchner funnel and adapter

     1    Silicone vacuum tubing

     1    Rubber stopper (size 15)

     1    Glass thermometer

     1    Filter paper

     1    pH paper

     1    Hotplate

     1    Glass stirring rod

     1    10-mL graduated cylinder

     1    50-mL graduated cylinder

     1    50-mL beaker

     1    400-mL beaker