F09 Final What to expect

F09 Final What to expect - What to Expect on the CHEM 232...

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What to Expect on the CHEM 232 final exam, scheduled for 6:30 p.m. Monday, December 14 The exam is a 10 question multiple choice exercise covering Expts# 6-11, worth 50 pts, or 5 pts per question. There are six questions which address either understanding of the physical phenomena which are the bases for the techniques employed (distillation and gas chromatography) or the fundamental chemical principles behind the experiments performed. Four others require calculations or analysis of experimental data. You will have to analyze GC data and identify the species depicted in an IR spectrum. You will be given information about the specific locations of IR stretches and bending associated with specific functional groups. You will have ~45 minutes to complete the exam. FYI: Remember: the mid-term and final exams are ways to distinguish between those students who really understand the material and how tp apply it and those who don’t. Based solely on lab reports, where many reported answers earn most, if not all, credit because of communal input and/or TA assistance, 90% of students would have the essentially the same grade, despite dramatically different comprehension and mastery of the course content. The following reviews details of the course content which may prove to be useful in studying for the exam Distillation: Essential principle: understanding boiling point liquid molecules are in constant motion those at surface can escape into the vapor phase; and will continue to do so until a dynamic equilibrium between liquid molecules escaping and vapor molecules reentering the liquid phase is established If temperature rises, molecular motion, #molecules escaping and equilibrium vapor pressure all increase. The total pressure is the sum of the vapor pressure of the liquid and that of air When a temperature is reached at which equilibrium vapor pressure of the sample equals the total pressure, rate of evaporation increases dramatically, bubbles form and the sample boils Simple Distillation Allows separation of components if their boiling points differ by 40-50 O Fractional Distillation (section 4.3) When a liquid is composed of two volatile components, #molecules of X, Y in a volume of vapor is proportional to their respective partial vapor pressures x x x y y x y Mole fraction of each component: N = P / (P + P ); N / (P + P ) Partial pressures of each is dictated by Raoult’s Law: mixture boils when x y P + P = external pressure; boiling temperature is determined by the mixture x x x x composition: N = P = P N o y y y y N P P N o How does this play out theoretically?
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A liquid mixture will have a specific boiling point based on the mole fraction of each component in the mixture Applying Raoult’s Law, the relative composition of the vapor at that temperature, which is dependent on the relative volatility (measured by its bp), can be calculated. The composition of the vapor at that temperature will be richer in the more
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This note was uploaded on 02/03/2010 for the course CHEM ORGO 1 LAB taught by Professor Jones during the Fall '09 term at Maryland.

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F09 Final What to expect - What to Expect on the CHEM 232...

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