Stoichiometry, Product Yield, and Limiting Reactants

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

1. Preparation of 25% v/v Ethylenediamine in Deionized WaterExpand

   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. Note: Ethylenediamine is toxic, caustic, flammable, and corrosive. This solution must be prepared and used in a fume hood.
   • Prepare 200 mL of a 25% v/v solution of ethylenediamine in deionized water. Pour about 50 mL into a 250-mL beaker.
   • Place a powder funnel in a 50-mL graduated cylinder and measure 50 mL of ethylenediamine.
   • Transfer the ethylenediamine to a 200-mL volumetric flask. Add deionized water to the flask until the solution level reaches the line.
   • Add a magnetic stir bar to the flask, then place it on a stir plate, and mix the solution for approximately one to two minutes until it is homogeneous. Turn off the stir plate when finished.
   • Label a brown glass dispensing bottle ‘25% v/v ethylenediamine’. Remove the dispensing pump and use a funnel to transfer the ethylenediamine solution to the bottle.
   • Reconnect the glass dispensing pump with a 20 mL capacity to the bottle.
   • Retrieve the stir bar with a magnetic wand and set both on a paper towel to absorb the excess liquid. Store the bottle in a flammables cabinet until it is needed.
   • When finished, thoroughly clean the volumetric flask, graduated cylinder, funnel, and stir bar, using your lab standard practices. Store the ethylenediamine in its approved storage location.
2. Preparation of the LaboratoryExpand
   • Fill out labels for organic, aqueous, and solid nickel waste containers according to the waste disposal procedures of your institution. Place the labeled containers in an approved waste collection area.
   • Ensure that the following glassware and equipment are available at each workstation (we suggest that students work in pairs):

     2    10-mL graduated cylinders

     1    100-mL beaker

     1    400-mL beaker

     1    600-mL beaker

     1    800-mL beaker

     1    500-mL filter flask

     1    Glass stirring rod

     1    Büchner funnel (40-mL/83-mm)

     1    Filter adapter (size 4)

     1    Neoprene stopper (size 15)

     1    Rubber policeman

     1    Roll of lab tape with pen/marker

     Silicone tubing

   • Set out packages of circular filter paper and disposable 1-mL plastic pipettes so that each workstation has access to them.
   • Place at least 3 L of ice in an insulated cooler with a scoop and set out paper towels as needed.
   • Obtain a container of nickel chloride hexahydrate and set it by the analytical balances. Verify that the balances have a sufficient supply of weighing boats, clean spatulas, and laboratory wipes.
   • Fill five 100-mL polyethylene bottles with acetone. Place a squeeze bottle of deionized water and a bottle of acetone at each workstation.
   • Label five tall-form beakers with ‘25% v/v ethylenediamine’. Bring the labeled beakers and five watch glasses to the hood with the ethylenediamine solution.
   • When a student group is ready, use the glass pump to dispense 20 mL of ethylenediamine into a labeled beaker. Cover the beaker and carefully hand it to the students.