Lab3 - Lab3: Mixed Melting Points Purpose The purpose of...

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Lab3: Mixed Melting Points Purpose The purpose of this lab was to use a mixed melting point of an unknown and known compound in order to determine the identity of the unknown and to interpret the effect of impurities on the meting point range. Discussion Part 1 Each student was assigned with an unknown compound sample in a labeled vial to test the melting point. A small amount of crystal was transferred into two melting- point capillaries and placed in a heating devise called the Mel-Temp 3.0. By doing so, a melting point range could be observed. After each student repeated the procedure twice and had collected a good melting point range, he or she would report the value on the board in order to find another student with a similar range. The samples from both students were mixed together thoroughly with a stirring rod and placed into the Mel-Temp 3.0 to find the new melting point range. If the resulting range was exactly the same with the values of both compounds before mixing, the two compounds were identical. If the obtained melting point ranges were different, the two compounds were dissimilar and either soluble or insoluble with each other. If soluble, the intermolecular forces between the molecules of the liquid would be affected, hence altering the melting point range. If insoluble, the melting point range would still be different due to the fact that each compound had distinctive melting point ranges. Part2 Referring to Table 1, the crossed-out value was omitted due to the dramatic difference in the final temperatures (5°C lower or higher). The drastic differences might be caused by human error: A student might have prepared the wrong ratio in the first place. Individuals had different judgments on the exact point when the solid first
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began to melt, or when the crystals were completely dissolved into liquid. In addition,
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This note was uploaded on 07/23/2010 for the course CHEM Chemistry taught by Professor Nitche during the Spring '08 term at Berkeley.

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Lab3 - Lab3: Mixed Melting Points Purpose The purpose of...

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