Lab Practical Objective: Students will be given approximately 1.00 g of an unkno

Question

Lab Practical Objective: Students will be given approximately 1.00 g of an unknown solid mixture. The mixture will be primarily an unknown organic acid contaminated with a significant amount of an organic neutral compound. During the week of Nov 28, the students are required to separate and purify the organic acid. During the week of Dec 5, the recovered acids will be weighed, the melting point will be taken, and the samples will be returned to the instructor in a labelled vial. Rules: Students will work individually. Students will take the practical at the regular scheduled time. There will be no make-ups without an excused absence, with documentation. Students must have a complete procedure written out in their notebook when they show up for lab. The instructor will check notebooks as the students enter the lab. Anybody without a satisfactory procedure will not be permitted to enter the lab. For the purposes of planning the procedure, students may assume that there are 9 mmol of acid in their sample. To limit waste, each student will be given 20 mL of dichloromethane to use during the lab. Additional dichloromethane may be "purchased" from the instructor at a cost of 5 points per 5 mL. Students may discuss their procedures amongst themselves freely before entering the lab. Students may not discuss their procedures during lab. Instructors are not permitted to assist students with their procedures. Instructors may answer questions about any previous experiment. Instructors may assist with operating instruments, and may answer questions about safety or logistics. Instructors may replace missing or broken equipment, but will not issue extras of something which the student already has. Students' procedures must be completed by the end of the scheduled lab time. Materials: The following materials will be available for the students to use: Student drawer contents Small filter flasks (to be signed out from instructor) 20 mL Dichloromethane (provided by the instructor) Saturated NaHCO_3 1.5 M NaOH 6 M HCI DI Water Anhydrous MgSO_4 95 % Ethanol Hot plates Grading: 50 points total. The grading breakdown is as follows:

Explanation / Answer

Procedure;-

1. Dissolve the solid (mixture of organic acid and organic neutral compound) in 20ml Dichloromethane.

2. Add 20 ml of saturated NaHCO3 solution to the above mixture solution.

3. Shake well to extract all the acid in the aqueous solution. (since reaction of organic acid with sodium bicarbonate produces the congugate acid which has higher pKa than the organic acid itself it will form the product which will be soluble in aqueous solution, whereas neutral compound will not react with NaHCO3 and will remain in the organic phase which is Dichloromethane)

4. Now keep the solution on the hot plate and heat to 40 degree. (since the boiling point of DCM is 39.6 degree it will evaporate leaving neutral organic solid behind which is not soluble in aqueous solution)

5. Separate the solid which are fromed and not soluble in aquous mixture with filter flask

6. Crude solid which you obtained dry it on hot plate and take the weight (organic neutral solid)

7. Add HCl in the above solution after filteration. ( Adding HCl to the above aqueous solution result in reverse reaction producing the organic acid back which is not soluble in aqueous solution)

8. Filter the solids using filteration flask.

9. Dry the solids on hot plate

10. Weigh the organic acid

11. determine the melting point for both the separated solids.

Related Questions

Navigate

• Browse (All)
• Browse L
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.