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Essay on Recrystallization lab report

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Experiment 1: Recrystallization – Evaluation Summary

Last Name: Xavier
First Name: Jessica
Date: October 1st 2013
Lab Day/TA/Group: Wednesday(1:35pm)/Group A

Labs reports must be typed and chemical structures must be drawn with ChemDraw. Report must not exceed three pages (including this page). Page limit does not include any attached spectra or references.
** Deductions for hand written report/structures and exceeding page limit **

Report Breakdown Data/Results: _________________ /10

Discussion: _________________ /10

Report Total: _________________ /20

Other Lab Marks Performance: _________________ /6

Prelab Quiz: _________________ /3

TA Comments on Report/Performance
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Given the following solubility test results, which would be the best recrystallization solvent for Compound A? Why?
Ethanol: Cold – soluble; Hot – soluble
Water: Cold – insoluble; Hot – soluble
Benzene: Cold – insoluble; Hot - insoluble
Water would be the best recrystallization solvent for Compound A, because when doing recrystallization, it is important that the compound be very soluble at the boiling point, and hardly soluble at room temperature. If it were insoluble in hot temperatures the compound would not dissolve, where as if it was soluble in cold, crystillization would be a very unlikely process. To note, impurities should on the other hand be very soluble at room temperature and insoluble in hot solvent in order to be filtered out due to the fact they remain dissolved in the solvent where as the rest of the compound crystallizes when cooling.
2. How does recrystallization purify a solid?
-First a saturated solution is made(a compound containing impurities is dissolved in a hot solvent)
-Secondly, the solution is cooled slowly(the slower, the bigger the eventual crystals), allowing solubility of compound to drop(not impurities solubility however), starting the crystillization process. (to note, to start the crystillization of the compound a seed is often required which involves scratching the glassware until a nucleus of glass
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