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melting_points_updated - Share results • Part 3(done in...

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Melting Points Reading Williamson, Chapter 3, p. 38-51 on the theory and background of melting points, as well as experiments 2, 3, and 4 on pages 52-53. Parts 2 and 3 will be done in pairs. Time-saving hints If you know the expected melting point for a sample, raise the temperature of the bath very rapidly until the thermometer indicates you are within 15-20° of the melting point. Then cut back to a heating rate of roughly 2° per minute. For an unknown, prepare an extra trial sample tube. Raise the temperature of the bath very rapidly and note the general point at which the sample melts. Then do a careful determination on a fresh sample. Experiment Part 2 (done in pairs) – Melting points of pure urea and pure cinnamic acid. One partner takes a melting point of urea and the other, cinnamic acid.
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Unformatted text preview: Share results. • Part 3 (done in pairs) – Melting point of urea – cinnamic acid mixtures. One partner takes a melting point of a 1:4 mixture of urea and cinnamic acid, and the other, a 4:1 mixture. Share results. • Part 4 (done individually) – Each student takes a melting point of an unknown compound and determines its identity from the list of possible compounds on p. 54. Questions 1. Williamson, p. 59-60 - #2, 3, 4, 5, 6, 7, 9, 11, 12, 2. Answer True or False : • A pure compound has a sharp melting point. • The melting point of an impure compound is depressed and broadened, compared to a pure compound. • A charcoal contaminant depresses a compound’s melting point. Smith 1/03...
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