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Exp 16 Molar Mass from Freezing Point UPDATED

Exp 16 Molar Mass from Freezing Point UPDATED - Exp 16...

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Dept. of Chemistry Exp 16 – Molar Mass from Freezing Pt Depression 1 Note! Refer to your lab manual for the INTRODUCTION to this experiment. SAFETY PRECAUTIONS REMINDER ! Safety glasses and lab coats MUST be worn at all times while the experiment is in progress. CHEMICALS HAZARDS Naphthalene IRRITANT FLAMMABLE in molten (melted) state ! Be cautious when heating with the Bunsen burner. Sulfur IRRITANT! Consult your instructor if you are allergic to sulfur OR you are asthmatic. Materials Needed 10 g Naphthalene Timer Gas Lighter 1 g Sulfur Bunsen Burner Iron Ring Digital Thermometer Wire Gauze Ring Stand PROCEDURE A) Freezing Point of Pure Naphthalene 1. Obtain a digital thermometer, timer and powder funnel from your instructor. 2. In a tared 150 mL beaker, weigh out approximately 10 grams of naphthalene and transfer it to a 6- inch test tube using a powder funnel. 3. Place 500 mL of very hot tap water in a 600 mL beaker and assemble it as a hot-water bath. Clamp the 6-inch test tube so that it is well immersed in the bath. Heat the water with the burner to boiling until the naphthalene starts to melt. Once sufficiently melted, turn on the digital thermometer and place it in the test tube. 4. Shut off the flame once the temperature reaches approximately 90ºC. Carefully agitate the contents in the test tube with the thermometer until the naphthalene has completely melted. Allow to cool with the test tube immersed in the hot-water bath. 1 Adapted from Neil Jespersen, General Chemistry & Introduction to General & Organic Chemistry , 14 th Ed. John Wiley & Sons, 2013 – 2014. Edited by Dr. Ishwar Sadarangani, CHE 1121 Lab Supervisor
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5. Once the temperature drops to 85ºC, start the timer and begin recording the temperature every 20 seconds. NOTE! For optimum measurements, stir the solution constantly with the thermometer for a few seconds before recording the temperature.
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Exp 16 Molar Mass from Freezing Point UPDATED - Exp 16...

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