Benzoic acid extraction lab report PDF

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Lab report # 3 BENZOIC ACID EXTRACTION Name: Elder Jean Baptiste Date: 9/28/20 Purpose: The purpose of the experiment is to learn the methods of extracting an organic compound from two immiscible solvents in order to purify a compound containing impurities.

Introduction Extraction is a method that can be used to extract impurities from an organic compound by using two immiscible solvents. In this experiment, 30Ml of water and 30ml of methylene chloride is mixed into a separatory funnel. Once the solvents have separate due to different levels of density, 1ml of impure compound benzoic acid is added to the mixture of solvents. The compound is mixed and shake well until it is dissolved in the immersible solvents. After the mixture have settled the organic layer is drained and 1ml of is extracted and placed in a vial with a few scoops of sodium sulfate. Once it has evaporated the benzoic acid in the vial is weighed in order to calculate the amount recovered. After calculating the amount recovered the partition coefficient can be calculated. The portioning coefficient is expected to be greater than 1 since benzoic acid is an organic compound and therefor will dissolve better in methyl chloride then water. Like dissolves like.

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Methods and materials 1 . Ta b l eo fp h y s i c a l c o n s t a n t s

Chemical Name Benzoic acid

Che mi c a l s t r uc t ur e

Mo l . Wt ( g / mo l ) 1 2 2. 1 2

Methylene Chloride

8 4 . 9 3

Water

1 8 . 0 1

Anhydrous Na2SO4

1 42 . 0 4

Amo unt 1

3 0

30

#o fmol s

g . 0 08 2

b. p. Mp d ( ° C) ( ° C) g / ml 2 2 . 0 1 . 3 24 9 - 1 2 4 9 . 2 1 2 2 . 1

mL . 3 5

3 9 . 7 5 9 5 . 1 - 1 . 3 3 4 0. 0 9 7 . 0

mL . 6 0

1 0 0 . 0

2 s c o o p s n / a

0 . 0 0 . 0

. 9 9 5

1 , 42 9 8 8 4 - 2 . 6 6 8 8 5

Results: Calculate the partition coefficient for benzoic acid between methylene chloride and water?

(.630g)/(1-.630)= 1.702g/mL

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Discussion and conclusions: For my result, the calculated partition coefficient of benzoic acid was 1.702. Because the portioning coefficient is greater than 1 this tell me that my overall work is successful. It was expected that more benzoic acid would dissolve in methylene chloride because both benzoic acid and methylene chloride is organic. Although benzoic acid also dissolves in water, when given a choice it will prefer the methylene chloride due to its density and characteristics. Source of error 1 Based on the result too much of the benzoic acid remained in water. Improvement 1 I believe I could have waited a little longer for all the benzoic acid to travel from water the aqueous solvent to methylene chloride. Source of error 2 Basic human error. Improvement 2 Better equipment for more precise measurement of solvent and benzoic acid. Source error 3 N/A Improvement 3 N/A

References: 1. “PubChem.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine, pubchem.ncbi.nlm.nih.gov/.

2. “Liquids Distillation and Boiling Points.” Experimental Organic Chemistry: a Miniscale & Microscale Approach/John C. Gilbert, Stephen F. Martin, by John C. Gilbert and Stephen F. Martin, Brooks/Cole Cengage Learning, 2016, pp. 131–146.

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Questions 1. If you are uncertain as to which layer in the separatory funnel is aqueous when extracting an aqueous solution with an organic solvent, how could you settle the issue? Fill a pipette with water and place it in the center of the bottom layer. Once water is released in the solution it will either travel up or don’t form any bubbles depending on the density of the solvent. If the water travels up, then the bottom solvent is organic. If the water does not travel, then the top solution is the organic solvent.

2. Indicate which layer, upper (U) or lower (L) each of the following solvent will usually form when sued to extract a dilute aqueous solution. a. b. c. d.

Dimethyl ether :U Dichloromethane :L Chloroform :L Hexane :U

3. A reaction work-up for an aqueous reaction mixture calls for extraction first with dichloromethane and then addition of magnesium sulfate. What is the purpose of the magnesium sulfate treatment? Magnesium sulfate is being used as a drying agent. It will help the water in dichloromethane to precipitate.

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