chem 3a lab #3 - Experiment #3: Mixed Melting Points...

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Experiment #3: Mixed Melting Points Abstract: This experiment illustrated how various intermolecular forces can determine and often change a melting point of a given compound, and that mixed melting points can be utilized to identify an unknown compound with the melting point of the known. Intro: Melting point tests provide critical information that can be used to identify a particular substance and differentiate it from seemingly similar substances, based on other more superficial characteristics. A melting point can also indicate whether a substance is “pure” or not- if it in fact is compound of various substances with a range of melting points or if it has its own distinct melting point. Discussion: Part 1 of the experiment examined how mixed melting points can be used to determine that two unknown compounds are in fact the same compound. Two melting point capillaries were prepared with sample #16 and heated in the MelTemp at 60 ºC with increasing intervals of 2ºC per minute; melting was observed between 96.3-97.7ºC. Once this range was established, two additional melting point capillaries were prepared with sample #16, one with an observed melting point range of 95.9-97ºC (sample A), and one with an observed melting point range of 97-98.3ºC (sample B). A compound of sample 16 and sample A was heated in the MelTemp at 92ºC with increasing intervals of 1ºC per minute; melting was observed between 96.3-97.3ºC. A compound of sample 16 and sample B was heated in the MelTemp at 92ºC with increasing intervals of 1ºC per minute; melting was observed at approximately 92ºC (if not sooner). These tests confirmed that sample 16 was most likely the same substance as sample A, given their virtually identical melting point ranges. Sample 16 and sample B proved to be different
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substances given the strong depression in the mixed melting point. When compared to
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chem 3a lab #3 - Experiment #3: Mixed Melting Points...

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