Each of the following students obviously didn\'t do the pre-lab reading before s

Question

Each of the following students obviously didn't do the pre-lab reading before scenario described below, tell me what the student did wrong and what should have been done instead. coming to la b. After each Haylee was very rushed and still needed the mp of her pure microscale unknown. She filled her capillary tube with the proper amount of sample and placed it in the apparatus. She quickly ran the mp and was dismayed when not only did the observed mp cover a 6 C range, but was also higher than expected. Explain what she did wrong A. B. Matt was heating his methanol solvent in an E. flask on a hot plate to use for recrystallization. The TA came by and noticed he didn't have a stir stick or boiling chip in the flask and told him to use one please. Matt dropped a stick in the flask and suddenly the liquid exploded out of the flask. Oops! Tel me why that happened. What should he have done instead? C. PJ'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 the recrystallization procedure you would suggest she use here Sophia and her friend Nora have the same unknown solid. Sophia 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 Sophia'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 problemm D. E. Taylor was harvesting her beautiful, pure crystals via vacuum filtration from a methanol/water mixed solvent system. She poured the solution containing her crystals into the Büchner funnel. Then she rinsed her flask with some warm methanol and poured that over the crystals resting in the Büchner oops! Tell what happened and w Sam knows that he has one of 3 possible liquid unknowns: tetrahyrofuran (bp 65-67°C), ethyl acetate (bp 76-77°C), or toluene (bp 110-111 C). He sets up for a microscale bp determination and clamps the whole shebang in a water bath. Fifteen minutes late the water is boiling like crazy, but he has yet to see a single vapor bubble escape from the capillary tube. He double-checks his set-up and everything is fine so now he's totally confused. What must his unknown be and why? Break it to him gently...he doesn't want to feel like a total idiot. F. Explain why the boiling point of your unknown liquid is at the point when the last little bubble escaping from th G. e capillary tube appears to get sucked back into the tube. A good explanation will 1) explain ion, and 2) surely include where all those bubbles escaping were coming from and their likely composit the term vapor pressure.

Explanation / Answer

A.She should observed the mp apparatus carefully near theoretical mp range of her unknown (expected ) sample.Her mp is more than the theoretical because she missed the exact mp in hurry and mp is very sensitive and sharp property.Secondly her mp apparatus could be very hot and she didn't checked it's temp and when she put the sample into it the sample melted instantly as the temp. of apparatus is more than the mp of sample.

She should check the mp apparatus and should have a close watch on the sample during mp measure.

B.He should add boiling chips by removing the burner and after a little cooling of the solution.As the solution was hot the gas present in the pores of chip reacted with the Superhot solution and the solution bumped out .

C. Recrystallization should done in the solvent from which the pure substance can extracted easily .She should use ethanol for Recrystallization process as it is volatile and during cooling will evaporate leaving behind pure substance.She can use water also but ethanol is more suitable.

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