Lab 6, Purification:Extraction PDF

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Mohammed Abdelrehem April 2, 2019 Professor Zdarvkovic CHEM 121 Purification using Acid-Base extraction Lab Report Purpose: The purpose of this lab was to be able to determine whether or not a certain organic compound was soluble in water, acid, or base. After figuring out the solubility we would be able to figure out the unknown solution using our knowledge of chemistry. Finally, we were able to recrystallize the reaction and use it to determine if we were using pure benzoic acid (can refer to lab day 5 for procedure in melting tubes and vacuum filtration). Chemicals & Equipment:

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Part 1: o Benzoic acid, cholesterol, 4-tert-butylphenol, and meta-aminoacetophenone (should be in numbers unknown) balance, water, 1 M NaHCO3, 1 M NaOH, 1 M HCl, 3 M NaOH, 3 M HCl, test tubes, universal pH paper.

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Part 2: o Ethyl acetate, impure benzoic acid, separatory funnel and ring stand, Büchner funnel with filter paper.

Summary Procedure: First and foremost, using 4 large test tube place about 5 mL of water, 5 mL of 1 M NaHCO3, 5 mL of 1 M NaOH, and 5 mL of 1 M HCl in separate test tubes. Next, using the unknown compound assigned to you place about 0.1 g in each test tube. Swirl around until you

noticed in which molecules it did dissolve and which it didn’t. Record your observations. Next using either 3 M NaOH or 3 M HCl add it to the solution to neutralize either the base or acid present. You then use pH paper to figure out whether or not the solution has gone through and the base has changed to acid or vice versa. Record your observations and then try to determine what compound you had. You can now move on to the second procedure. Using 1.6g of benzoic acid dissolve it in 40 mL of ethyl acetate. Place this solution in the separatory funnel, then add 40 mL of sodium bicarbonate. Swirl the solution in the separatory funnel gently, but in a slightly vigorous manner. After swirling for a little flip, the funnel over holding the top and then opening the stopcock to let the air out and observe how the air comes out. Repeat these 3 times. Then remove the sodium bicarbonate from the solution in a beaker and move on to the adding HCl to that beaker until some type of precipitate form. Place the beaker in an ice bath for sometimes. Then set up the vacuum filtration apparatus and separate the compound to form pure benzoic acid. When all is separated place it into a watch glass and in the oven for about 15 minutes. Weigh the final solution when removed from the oven and figure out the percent yield. Comparing your final amount to your initial amount. Finally, using the melting point apparatus figure out whether or not the benzoic acid is pure. Data/Results: Initial (g) 1.6g

Final (g) Calculation 0.94 g 0.94/1.6=0.5875*100% Percent Yield of Benzoic Acid Melting Point of Benzoic Acid

Sample of Benzoic Acid Pure Sample Purified sample in lab

Percent Yield 58.75%

Melting Point (degrees Celsius) 122 Roughly 99-101

Solubility in Acids and Bases Table Compound

1 M HCl

1M

Water

1M

3 M HCl

3M

Classification

1

2

3

4

NaOH No dissolve Dissolve

No

NaHCO3 Dissolve

(-)

No

dissolve

(+)

dissolve (-) (+)

No dissolve No

(-) No

No

N/A

N/A

Cholesterol

(-)

dissolve

dissolve

dissolve (-)

Dissolve

(-) No

(-) No

No

No

Dissolve

Meta-

(+)

dissolve

dissolve

dissolve (-) dissolve (-) (+)

aminoacetophenone

(-) No dissolve No

(-) No

No

4-tert-butylphenol

(-)

dissolve

dissolve

dissolve (-) dissolve (-) dissolve (-)

(-)

(-)

(+)

No

NaOH Dissolve

No

Benzoic Acid

Discussion: After finishing part 1 of the experiment we can make and educated guess for the names of the unknown compounds by simply determining whether it was soluble in acid or base. compound 1 was most likely benzoic acid, 2 was cholesterol, 3 was meta-aminoacetophenone, and the last compound had to be 4-tert-butylphenol. Since the first compound is soluble in bases, we can predict that it is an acid and the only acid present is benzoic acid. For compound 3, we can assume that it is meta-aminoacetophenone, since it is only soluble in an acid and because it contains a RNH2 group allowing it to be soluble in HCl. For compound 4 since it was a larger organic compound and there was an equal sharing of electrons meaning it was nonpolar, we can assume that it is insoluble. This led us to the conclusion that compound 4 is 4-tert-butylphenol. After finishing the second part of the experiment we can come to the conclusion that our purified sample of benzoic acid wasn’t completely pure since it had a lower boiling point than the pure

benzoic acid. This can also help us conclude that the extraction process is not always 100 percent accurate....