chem 3a lab 6

chem 3a lab 6 - Riti Gupta Chem 3AL Section 112 Experiment...

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Riti Gupta Chem 3AL Section 112 Experiment 6 : Recrystallization and Melting Points: Recrystallization of an Unknown Solid and Decolorization of Brown Sugar Part 1 : After dissolving some of the unknown (unknown B) in each of the five solvents, it was found that the unknown was insoluble in all of them except for diethyl ether. At the beginning it seemed as if the unknown was insoluble in diethyl ether as well, but on closer inspection, the unknown was actually slightly soluble. In the sand bath, the unknown was soluble in hot ethanol solvent, hot acetone solvent, and hot water solvent, but insoluble in hot hexane solvent. Diethyl ether was not used. In the ice bath, crystals recovered in ethanol, hexane, and water, but not in acetone. Crystals most readily appeared in ethanol. Ethanol was chosen as the solvent for recrystallization because, based on the solubility tests done, the unknown was very soluble at ethanol’s boiling point and was much less soluble in ethanol at ice-water temperature because it came out of solution as the mixture cooled. These are characteristics of a suitable solvent for recrystallization. After four recrystallizations of the unknown in ethanol, the percent recoveries were 84%, 71%, 70%, and 127%. The reason for the high percent recovery for the last
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This note was uploaded on 12/01/2009 for the course CHEM 3AL taught by Professor Li during the Fall '08 term at Berkeley.

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chem 3a lab 6 - Riti Gupta Chem 3AL Section 112 Experiment...

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