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(SP%2710%20235)%20Quiz%202 - good or bad whether the...

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Chemistry 235 Due the week of Jan. 25-29, 2010 Organic I George A. O’Doherty Quiz #2 Name There is a total of 10 points for this quiz. Answer all questions in the space provided. [I] (5 points) Using the same sample and identical Mel-temp apparatuses two students ( A and B ) measured two different melting temperatures. Student A measured a m.p. of 100°C, while student B measured a m.p. of 102°C. The T.A. noticed that student A ’s Mel-temp was heating the sample at a faster heating rate. a) (2 point) Given this information which m.p. measurement (Student A or B ) is more likely to be the correct m.p.? b) (2 points) Why? c) (1 point) If you believed the actually m.p. was 103°C, which of the following action would most likely lead to the measurement of the correct higher temperature (circle the correct answer below)? A. To measure the m.p. using a faster Mel-temp heating rate. B. To measure the m.p. using a slower Mel-temp heating rate. [II] (5 points) Indicate (by writing either
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Unformatted text preview: good or bad ) whether the following conditions are good or bad for crystallization? a) Using two solvents (like hexane and water) that are immiscible with each other (1 point). b) Dissolving the compound in a minimum amount of a solvent in which the compound is very soluble and then to slowly add a second miscible solvent in which the compound only slightly soluble (1 point). c) To slowly allow a volatile solvent to evaporate from a solution of the compound until crystallization occurs (1 point). d) To dissolve the desired compound in a minimum amount of a hot solvent and then to slowly allow it to cool until crystallization occurs (1 point). e) To dissolve the desired compound in a solvent mixture (where one solvent is a good solvent yet volatile and the other is a poor solvent and non-volatile) then to slowly let the good more volatile solvent evaporate until crystallization occurs (1 point)....
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