Document 39-4 - lab PDF

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UNT_SPRING 20201 3210

3210 Organic Chemistry I_ Lab Report

Student name: Vera Iseid Student ID: 11457460 Section/TA name :303/ Sheikh M S Islam Submission due: June 15-2021

Lab5:

Liquid Extraction of Benzoic Acid

and Naphthalene Mixture • The Objective of the Experiment: The purpose of this experiment to separate a mixture of two solid compounds. Benzoic acid and Naphthalene. Both are soluble in diethyl ether organic chemistry. Both are insoluble in water. we have a mixture compound that mixture of compound has acid, could be benzoic or similar • reference table: Chemical Benzoic Acid

Mass

Melting point

Solubility inSoluble in water

25 milligram

80 C-90C

Naphthalene

90 milligram

121C-125 C InSoluble

Structure

Material: • Glass wear, gloves, goggles, test tube, Arlo Meyers vacuum flask, beakers, benzoic acid naphthalene diethyl ether, three molar hydrochloric acid, sodium sulfate. • Experimental Procedure: 1. 2. 3. 4. 5. 6.

First 300 milligrams of our mixture. Place the mixture into the center feature tube with 5 ml of organic solvent. Shake It Until id completely dissolved Add 5ml solvent. (You can notice the separation). Then cap it and shake it. leave it couple minutes. Labeled the Erlenmeyer flask.

UNT_SPRING 20201 3210

3210 Organic Chemistry I_ Lab Report

7. Number 1 will be the bottom layer use the spec pen. 8. After extracting the bottom layer into the Erlenmeyer flask. 9. Cool it down with ice bath. 10. The pour the organic layer into the second liner flask. 11. Wait 10 minutes. 12. After the aqueous layer is cool. Add 5ml of hydrochloride acid to neutralize sodium hydroxide. 13. Mix it with the stir 14. Check the PH value with PH paper. 15. Set the vacuum flask, fold a piece of filter paper into the funnel. 16. Filter the product from aqueous layer and try to add all the left by using cold water. 17. Start to decant the organic layer, then pour out the liquid leave all the sodium sulfate at the bottle. 18. Set it into hot bath to evaporate the organic solvent. 19. Dry the benzoic acid with paper make sure it is dry very well. 20. Weight the. the benzoic acid 25 milligrams. The naphthalene 90 milligrams 21. Now the melting point. For naphthalene and benzoic acid.

• Prelab Questions: 1.What is significance of understanding the miscibility of solvents during Liquid-Liquid extraction process? Use an example to explain (do not use the lab procedure). We know, in the process of liquid-liquid extraction, constituent liquids are separated from a mixture of two or more liquids. In this process an immiscible solvent, immiscible in the liquid mixture is passed through the mixture of liquids. The solute, in the liquid mixture miscible with the immiscible solvent, gets dissolved in the solvent. The constituent liquid of the mixture, which is not miscible, with the solvent, remains in the liquid mixture thereby. Thus, after liquid-liquid extraction, the constituent liquids of a liquid mixture get separated, in two layers, i.e., one constituent liquid (immiscible in the given solvent) in one layer containing the liquid mixture, and another constituent liquid (miscible with the solvent) is extracted in another layer of the immiscible solvent, and are therefore separated out

2.What is the reason for altering solubility of benzoic acid in this experiment?

UNT_SPRING 20201 3210

3210 Organic Chemistry I_ Lab Report

This experiment allows you to separate a solid-phase mixture consisting of. using Separatory Funnel extractions. Since each of these chemicals have similar solubilities in water and ether, you can affect a separation their chemical properties. For example, benzoic acid is insoluble in water, but the benzoate ion is soluble in water. Therefore, under neutral conditions, the benzoic will partition into the ether layer. Adding NaOH will neutralize the benzoic acid producing the benzoate ion, which now goes into the aqueous layer, leaving other two organic compounds in the ether.

• Observation and Results:

• •

When add 5ml of solvent, notice some separation currently. And it produces gas acid base reaction of the benzoic acid, and the sodium hydroxide does not get trapped in the tube. After pouring the organic layer will notice that have water in organic layer. After Using PH paper, the value is 3 or 4 acidic.

•

Flow chart

•

UNT_SPRING 20201 3210

3210 Organic Chemistry I_ Lab Report

• Data: Mixtures Mass Benzoic acid 25 milligram Naphthalene 90 milligram • Conclusion:

Melting point 80 C-90C 121C-125 C

Recovery 54.3 % 6.83 %

We separated mixture of benzoic acid and naphthalene using method liquid liquid extraction. Because both are soluble in organic solvent diethyl ether, and both are insoluble in water. We react benzoic acid with the base and form benzoate anion more soluble acid. Which then separated into aqueous layer leaving our naphthalene and the organic layer.

Post lab Questions:

UNT_SPRING 20201 3210

3210 Organic Chemistry I_ Lab Report

1. A mixture of 3 substances that includes Naphthalene, Aniline, and Benzoic acid is supplied. You are asked to outline an experimental strategy for separating these three substances from the mixture. Assume all substances are soluble in ether. Explain your rationale. A flow chart clearly showing the individual steps is required for full points. 1. Dissolve the mixture in ether. 2. Add aqueous sodium hydroxide. Benzoic acid reacts with sodium hydroxide to give water soluble sodium benzoate. Hence benzoic acid enters aqueous layer in the form salt, sodium benzoate. This layer is separated by using separating funnel. C6H5COOH + NaOH ------------> C6H5COONa + H2O In the ether layer there are Naphthalene and Aniline. 3. Add aqueous hydrochloric acid solution to the remain ether solution. Aniline reacts with hydrochloric acid to form water soluble anilinium chloride salt. Hence aniline enters aqueous layer in the form of salt, anilinium chloride. This aqueous layer is separated by using separating funnel. C6H5NH2 + HCl ------------> C6H5NH3^+Cl^4. In the ether layer there is only Naphthalene. So that we can separate the three organic compound presents in the mixture.

• References: Chapter 7 from "Macroscale and Microscale Organic Experiments," 6th or 7th Edition by Kenneth L. Williamson and Katherine M. Masters.

Bonus questions: 1. How many grams of sodium hydroxide does it take to create 100 ml of 3 molar sodium hydroxide? Given: Molarity of sodium hydroxide =3M Volume of solution =100mL

UNT_SPRING 20201 3210

3210 Organic Chemistry I_ Lab Report

Amount of sodium hydroxide in grams =? First, convert volume of solution in liter 1mL=0.001L 100mL =0.001L*100mL/1mL=0.1L Now calculate molar mass of NaOH = sum of atomic masses of Na, O and H = 22.99g/mol+15.999g/mol+1.0078g/mol =39.9968g/mol Using formula (3) as given above, we get Molarity of NaOH = mass of NaOH /molar mass of NaOH * volume of NaOH solution in liter Molarity 3M can be written as 3 mol/liter (according to definition of molarity as given above) 3mol/liter =mass of NaOH /39.9968g/mol*0.1L Mass of NaOH = 3 mol/liter *39.9968g/mol*0.1L=11.99904g(units mol and liter cancelled out) Answer: After rounding off, amount of NaOH =12g

2. Why is it important that we make sure our solid is fully dry before weighing and measuring melting point? When measuring a melting point, you are technically obtaining a melting "range". Because something usually starts melting at certain temperature and finishes at a higher temperature so maybe something has a melting range of 94-98 C. So, if the sample were not properly dried you may have liquid in them prior to your sample melting that may distort your melting range. Beyond that, impure samples of a substance will have a lower and broader melting range which also supports my prior statement. Also, many organic crystals that are prepared in Labare sometimes rinsed with another organic liquid for instance, cold hexanes. If hexanes were left in with the melting point sample, they would drastically alter the melting range as well.

3. What is the top layer and what bottom? The top layer is organic layer naphthene....