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Unformatted text preview: Determination of Molar Mass by Freezing-Point Depression Introduction The purpose of this experiment is to investigate the effect of dissolved substances on the freezing point of the organic solvent cyclohexane, determining the melting point in the process. After calculations are done the molar mass the unknown will be evident. Procedure/Observations Part I The experimental assembly was first prepared using a clean, dry 200 mm test tube and a two-hole rubber stopper. A thermometer and a 50-cm copper wire was then put into the rubber stopper, making sure the copper wire can move freely to stir the solution. A 300- mL Erlenmeyer flask was attached to a ring stand to reduce the rate of warming during the procedure. A cold bath of ice, water, and rock salt (45 g) was then prepared in a 400- mL beaker. Part II 55-mL of cyclohexane was then put in a dry beaker and covered with a watch glass to retard evaporation. Then we used a dry 25-mL volumetric pipet and rubber bulb to transfer 25-mL of the cyclohexane into the test tube assembly. The assembly was then placed into the cold bath. The cyclohexane was stirred constantly until a slush forms, at...
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- Spring '08