Experiment 4A: Determination of a Partition Coefficient for Benzoic Acid in Methylene Chloride and Water, and Experiment 4B: Solvent Extraction I: Acid-Base Extraction Using the System Benzoic Acid, Methylene Chloride, and Sodium Bicarbonate Solution
The purpose of this experiment is to familiarize oneself with the general procedures determining a partition coefficient at the microscale level and learn in weighing milligram quantities of materials on an electronic balance, the use of automatic pipets, the use of transfer pipet, and the use of a vortex mixer. Also, to familiarize oneself with extraction…show more content… Experiment 4B
After dissolving benzoic acid in 1.0mL CH2Cl2 and 1.0mL 10% NaHCO3 solution, two layers are created, the top layer is 10% NaHCO3 solution and the bottom is CH2Cl2.
After putting the CH2Cl2 to a beaker containing the drying agent anhydrous sodium sulfate, a sticky white solid was recovered.
After heating, a very few amount of solid white-greyish benzoic acid was recovered.
1. The purpose of sodium sulfate is as the drying agent. I rinsed the sodium sulfate with additional methylene chloride to have a more accurate amount of benzoic acid in case the benzoic acid precipitated.
2. a. It is not necessary because as the drying agent it does not influence the substrate concentration.
b. If it is too much the all of the solution will precipitate including the benzoic acid. If it is too little than then it will take a long time to heat the solution in order to acquire the benzoic acid.
3. a. The first error will be when transferring the benzoic acid from the weigh paper to the vial. The benzoic acid is spilled. Then, the second one will be when pipetting and transferring the methylene chloride because I might spill some of the methylene chloride. The third one will be when pipetting the two layers, either I could not pipet all of the bottom layer or I accidentally pipet the top layer.
b. As I mentioned above that I spilled some of the benzoic acid therefore the initial mass