exp 3.docx - Mariem L Maghsoodi Chem220L Professor Heriberto Rivera Recrystallization of solid compounds Objective To separate benzoic and acetanilide

exp 3.docx - Mariem L Maghsoodi Chem220L Professor...

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Mariem L Maghsoodi Chem220L Professor Heriberto Rivera 9/11/19 Recrystallization of solid compounds Objective To separate benzoic and acetanilide impurities by the technique recrystallization and to calculate the percent recovery of benzoic acid after recrystallization. Abstract The purpose of this experiment was to purify a sample of organic compound that are solid at room temperature, and to dissociate the impure sample in the minimum amount of an appropriate not solvent. The mass of the benzoic acid was 0.500g. The mass of recrystallized benzoic acid & weighing paper was .514g. The percentage recovery was 80.95%. The solution was 80.95% pure, and 19.05% was impure substance. The melting point of the recrystallized benzoic acid was 114.0-113.0 ºC which means that the substance is pure. Introduction Organic compounds synthesized in the laboratory or isolated from natural sources are often contaminated with impurities. Recrystallization is a method for removing impurities from organic compounds that are solid at room temperature. This method relies on the observation that the solubility of a compound in a solvent generally increases with temperature. Conversely, the solubility of a compound will decrease as a solution cools until the solution becomes saturated, and crystals form. This experiment was conducted in order to explore the methods of recrystallization and in order to determine the melting points of various solids. Recrystallization can produce very pure
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compounds. When a warm solution of a compound cools and reaches the saturation point, small seed crystals of the compound form in the solution. Slowly, additional molecules of the compound attach to the seed crystal and the crystals grow. Since molecules in the crystals have a greater affinity for other molecules of the same type than they do for any impurities, the process of crystal formation gives rise to relatively pure crystals. The impurities originally present in the
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