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Unformatted text preview: Version 118 Exam 1 mccord (51625) 1 This print-out should have 26 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points Ethyl alcohol (CH 3 CH 2 OH) is/is not soluble in water. 1. is; ethyl alcohol exhibits dipole-dipole and H-bonding interactions with water. correct 2. is not; ethyl alcohol exhibits dispersion forces which are insufficient for dissolving. 3. is not; ethyl alcohol is an ionic compound with a hydroxide group and hydroxides are insoluble. 4. is; all organic molecules are soluble in water. Explanation: The oxygen on ethyl alcohol has two lone pairs and two polar bonds. Thus, it can form dipole-dipole and H-bonding interac- tions with polar water. 002 10.0 points Solution A contains 0.5 grams of solute A and solution B contains 0.5 grams of solute B (both A and B are nonelectrolytes). Other than the solutes, the solutions are identical (volume, temperature, etc .). Now you mea- sure the osmotic pressure of each solution and find that the osmotic pressure of solution B is twice that of solution A. What is the relation- ship between the molecular weights of solutes A and B? 1. The molecular weight of solute A is twice that of solute B. correct 2. The molecular weight of solute A is four times that of solute B. 3. The molecular weight of solute B is twice that of solute A. 4. The molecular weight of solute B is four times that of solute A. 5. The molecular weight ratio cannot be determined from this experiment. Explanation: Because the solution with B has twice the osmotic pressure, it must also have twice the number of dissolved particles (number of moles of B). The only way to have more moles for B (knowing the same mass of A and B was used) is that B has a smaller molecular weight than A. For the osmotic pressure to be ex- actly twice that of A, the molecular weight of B must be half that of A which is the same as A being twice that of B. 003 10.0 points Carbon Dioxide 3 1 4 2 A B 200 250 300 350 400 10 10 1 10 2 10 3 10 4 Pressure,bar Temperature, K A sample of carbon dioxide is stored at 10 4 bar and 250 K. This sample is then decompressed to 10 bar at constant temper- ature. Then, at constant pressure it is heated to 400 K. Next, it is compressed at con- stant temperature to 200 bar. According to the phase diagram, how many phase transi- tions has the carbon dioxide gone through, and what is its final state? 1. 3, gas 2. 2, supercritical fluid correct 3. 2, liquid Version 118 Exam 1 mccord (51625) 2 4. 2, gas 5. 3, supercritical fluid Explanation: Navigate through the diagram through each process. In the first decompression, the solid is decompressed and becomes a liquid and then a gas (2 phase transitions). Upon heating, it becomes a supercritical fluid (no phase transitions)....
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This note was uploaded on 07/12/2011 for the course GOV 365L taught by Professor Liu during the Spring '08 term at University of Texas at Austin.
- Spring '08