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01-26-2010 01;05;04PM - Version PREVIEW — Exam 1 —...

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Unformatted text preview: Version PREVIEW — Exam 1 — JOHNSON — (52390) This print-out should have 30 questions. 5. II, III, and IV Multiple—choice questions may continue on the next column or page — find all choices 6. I, II, and IV before answering. 7. I, and III LDE Temperature and Phase Changes 001 001 6.0 points In general, decreasing the temperature makes which phase transitions more likely to occur? Explanation: 1' condensation, fUSiOD: deposition As vapor particles encounter the surface of a solution and condense, their energy released 2- evaporation, fusion, sublimation makes another particle move as a vapor. This is an equilibrium process, and it is tempera- 3- evaporation, dBPG‘SifiOna freezing tare dependent. As IMF decreases, the va— por pressure increases, since only weak forces 4' sublimation, condensation, freezing will be holding a substance together as a liq— uid. Vapor pressure also only o'ccurs at the 5- condensation, freezing, deposition cor— surface, so it does not matter how deep the rect liquid phase is. Explanation: ' Phase changes are equilibrium processgs LDE Salt Dissolution Theory 001 and are thus temperature dependent. Also, 003 6‘0 points the AH and AS always have the same sign. Which of the following is a possible combina— Lowering the temperature makes exothermic tion 0f values for _AHlattice: Athdration and phase transitions more likely - freezing, con- AHsolution: respectively, for a 3311? whose d15- densatiofl and deposition. solution is endothermic. 1. +550, —480, and + 1030 Id - moi—1, LDE Vapor Pressure Theory 001 002 5.0 points 2. —900, —900, and — 1800 kJ-mol'l, Consider the following statements. Which 3‘ +640! ‘620’ and +20 1"] “1101—1: cor- are true? rect I) Vapor pressure is an equilibrium phe- nomenon. 4. —450, +400, and — 50 k3 - moihl, II) The smaller the IMF, the smaller the vapor pressure. III) The volume of a liquid does not affect the vapor pressure Explanation: IV) Vapor pressure is temperature depen- AHsolnt-ion : AHlottioe + AH hydration ‘ the dent. problem stipulates that AHsogmwfi be positive (endothermic) and this limits the values the 1. I, II, III, and IV other two terms can have. 2. I, III, and IV correct LDE Phase Diagram Interpretation 001 004 6.0 points 3. III, and IV According to the given phase diagram for carbon dioxide, what are regions 1, 3 and B 4. I, II, and III respectively? Carbon Dioxide ...
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