Andrade_Experiment2 - Chem 262L Francisco Andrade...

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Chem 262L Francisco Andrade Purification of an Unknown by Recrystallization Purpose: The purpose of this experiment is to recrystallize an unknown organic acid to obtain it in its pure form. Procedure: To a beaker, 10 mL of ethanol was added and heated to boiling. About 500 mg of the unknown organic acid was added to a 10 mL Erlenmeyer flask, along with slightly more than the minimum amount of hot ethanol needed to completely dissolve the solid. The hot solution of the unknown was filtered by hot filtration using a fluted piece of filter paper placed in a stemless funnel. The solution was passed through the filter paper and collected in an Erlenmeyer flask containing 1-2 mL of boiling ethanol and a boiling chip. Water was added to the liquid obtained in the Erlenmeyer flask until it became cloudy. No more than two to three times the volume of ethanol used to dissolve the unknown was added. The solution was cooled to room temperature and covered with a watch glass to keep out airborne impurities and prevent evaporation. The solution was transferred to an ice bath once the temperature of the solution had reached room temperature. If no crystals were observed, then seeding or scratching the inside of the flask was done. The crystals were examined for color and filtered via suction filtration. Chilled water was used to rinse the crystals from the sides of the flask into the Buchner funnel. The recovered unknown was weighed, and the filtrate was concentrated by boiling and cooled to form crystals. The resulting crystals were isolated, washed, and dried. This second crop was weighed, and the
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This document was uploaded on 11/04/2011 for the course CHEM 262 at UNC.

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Andrade_Experiment2 - Chem 262L Francisco Andrade...

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