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Post-lab Questions - Recrystallization.docx

Post-lab Questions - Recrystallization.docx - EXPERIMENT#4A...

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EXPERIMENT #4A: Tun Nef 1. Show the steps for the recrystallization for a compound with an insoluble impurity. -For the recrystallization of samples with insoluble impurities, using the suitable solvent is necessary. The first step for recrystallization is dissolving the sample with the chosen solvent and heating it or addition of heated solvent into the sample using Erlenmeyer
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flask. For the benzoin sample in this lab, 9 mL of 95% ethanol was mixed with benzoin and heated while 15 mL of preheated water was added into vanillin sample. After the dissolving process, the mixture is cooled with the room temperature and used gravitational filtration to separate the insoluble impurity. The sample starts to crystallize after a few minutes and impurities are being filtered out as a liquid. Then, the second step which is vacuum filtration using Hirsch funnel is used to filter the rest of remaining impurities and evaporate the solvent to make the crystals dry. Then, using the melting point and the percent recovery to determine the purity of the samples.
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