lab 3 discussion

lab 3 discussion - As you can see substance A has a lower...

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Experiment 3: Mixed Melting Points Part I A general theory of chemistry is that when two different substances are mixed, the resulting substance’s melting point is lower than that of either of the separate substances. After determining the melting point of my own unknown substance, I compared the melting point to the rest of the class’s data. After finding two students with similar melting ranges we mixed our substances. I could then use the mixed melting points to find which student had a different solid to mine because the resulting mixed substance’s melting range would be lower than my own solid’s melting range. In addition to a depressed melting point, the melting range of a mixed solid is broader than the melting range of an individual solid. In order to determine another student in the lab room with an unknown solid identical to mine I simply had to find a student with a substance that, when mixed with mine, had the same melting range as our original two substances. Part II
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Unformatted text preview: As you can see, substance A has a lower melting point than substance B. But the mixture of them both has a lower melting point than either of the substances separately. Based on the class data, the eutectic point is a mixture of 30:70 or 40:60, with a final melting point of 65.8°c. It is the ratio of the two substances that has the lowest boiling point. Part III The final melting point of my unknown mixture was 62°c. I estimate that my mixture was 40:60 or 30:70. Both of these ratios have the same class data. In order to determine the composition of my unknown mixture I would create a 40:60 mixture and mix that with my unknown mixture. If the melting range of this resulting mixture is lower than the melting range of my unknown mixture, then I can conclude that my unknown mixture is not a 40:60 composition. I could then create a 30:70 mixture and repeat the previous steps. If my unknown mixture were indeed a 30:70 composition, then the melting range would remain constant....
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This note was uploaded on 09/18/2011 for the course CHEM 3AL taught by Professor Li during the Spring '08 term at Berkeley.

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lab 3 discussion - As you can see substance A has a lower...

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