Fall 2017 CHEM 2583 Final Exam A Missing Structure S. Based on the melting point
ID: 104935 • Letter: F
Question
Fall 2017 CHEM 2583 Final Exam A Missing Structure S. Based on the melting point ranges in the scheme below, what can be implied about the purity of sample A7 (5 points) Sample B >99% pure from a chemical supper mp. 132-135·C Sample A Synthesired in mp. 128-134 4. Upon completion of a laboratory experiment, a student has removed their lab coat, safety glasses, and gloves. The student realizes they forgot to quench and dispose of an aqueous HCl solution, so they add a solution of aqueous NaOH into the HCI solution, and pour the contents into the organic waste. Please list all the safety issues (if any) in this scenario. (10 points) 5. Based on the melting point ranges in the scheme above, what can be implied about the purity of sample A? (10 points) 6. List two common uses for Thin Layer Chromatography (TLC) 2 Points 6b) What are two common adsorbents used in column chromatography? How are they different? 2 Points 6c). Give two methods to visualize spots after they were developed on a TLC plate 2 Points 6d. Define Rf value and calculate Rf values for the reactant (A) and product (B) spots on the TLC plate shown. 4 pointsExplanation / Answer
6. *Purity of a sample can be carried out with TLC.
*TLC can be employed in isolation and identification of natural products.
*Reaction mixture can be examined by TLC to access whether the reaction is complete or not.
b)Silica gel and Alumina.As they give highly effective results in isolating the desired compounds from a mixture.
6c) If compounds are colored, no method is required.If not, then one of the methods can be used to reveal the spots.
Non destructive methods-UV active compounds can be viewed under ultraviolet lamps.Iodine chamber is also used.
Destructive methods- Compounds that are not uv active, there are several strains that can be used depending upon the nature of the compound. To use a strain, simply dip the TLC plate into the staining solution as quickly as possible and then immediately absorb the excess stain with paper and heat carefully until spots are revealed.
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