CHM2210L_Melting Points and Mixed Melting Points

CHM2210L_Melting Points and Mixed Melting Points - Anthony...

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Anthony Flores CHM 2210-Lab report # 1 September 20, 2010 Melting Points and Mixed Melting Points Purpose: Firstly, measure the melting of pure benzoic acid and pure mandelic acid to develop the necessary skills in order to get accurate melting point ranges. Secondly, to identify an unknown compound using mixture melting points. And finally, taking a melting point is a good model for future organic laboratory procedures. Procedure: I. Measure the melting point of pure benzoic acid and mandelic acid. Take 2-3 mg of pure benzoic acid on a watch glass and crush it into a fine powder. Obtain a capillary tube and tap the open end onto the powder of the pure substance. Firmly pack the powder into the closed end of the capillary tube by tapping the closed part on the top of the table. Keep doing it until you observed 1-2 mm of benzoic acid. In a small beaker add 5 – 10 mL of silicon oil. Place the beaker on the plate and inside the beaker; place the thermometer and the capillary tube. Start heating the capillary tube close to 100 ºC. Then slow the rate to 1-2 ºC per minutes. Caution: DO NOT heat the capillary tube too quickly, it can result an inaccurate melting point measurement. Record the temperature at which the liquid first appears, and the temperature at which the entire sample becomes liquid.
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Pure benzoic acid melts at 122-123 ºC, and a normal rage of error for melting point is ± 3ºC. When melting point is acquired move the beaker carefully to the corners of the plate so it cools down, and throw the capillary tubes in the glass disposal. REPEAT the process for RS-mandelic acid. Remember that mandelic acid melts at 120 – 122 ºC. II. Identify an unknown compound by melting point Obtain an unknown compound from your instructor. RECORD the unknown compound number in your data page. REPEAT
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CHM2210L_Melting Points and Mixed Melting Points - Anthony...

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