Prelab 2

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School

University of Louisville *

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Course

343

Subject

Chemistry

Date

Dec 6, 2023

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docx

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1

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Avery O’Brien CHEM 343-76 Prelab Questions for Lab 2 (10 points) 1. Heba and her friend Nora have the same unknown solid. Heba has progressed a little faster with the purification process, but now she is standing around twiddling her thumbs because no crystals are forming, even over an ice bath. Nora decides that Heba’s problem is too much solvent. Determined not to have the same problem, Nora uses a minimal volume of hot solvent to dissolve her compound before doing the gravity filtration step. She begins to pour her hot solution into the filter cone of a long-stemmed funnel and ….is that missed impurities sprouting up on the funnel walls? Why so shiny? Explain what Nora did wrong and how to fix the problem. List 2 things she should do. 3pts Nora used a long-stemmed funnel when she should have used a stemless funnel when performing the gravity filtration. In order to get the crystals off the funnel walls she could use distilled water to try and release the crystals from the side. Additionally, Nora could use a clean microspatula to free the crystals from the walls. 2. Neel’s unknown solid 1) dissolves in hot ethanol, 2) is essentially insoluble in hexane, and 3) is insoluble in cold water, but sparingly soluble in warm water. Outline a recrystallization procedure. 4pt A mixed solvent will have to be used for recrystallization. First Neel should dissolve his unknown solid in hot ethanol. Then after letting the solution cool and begin to crystallize, cold water should be added to encourage more crystal growth, making the solution cloudy. Then a gravity filtration and vacuum filtration can be performed to completely isolate the crystals. Afterwards the crystals can be washed to finish the purification. 3. Where is the capillary tube placed for the microscale boiling point determination and how is it orientated? What is collected in the capillary tube? 3 pts The capillary tube is placed in the test tube for microscale boiling point determination and is oriented so the opening of the capillary tube is pointing towards the bottom of the test tube and is upside down. When the boiling point is met, liquid will collect in the capillary tube
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