EXAM 1 - Mantooth, Marlo Exam 1 Due: Feb 2 2007, 1:00 pm...

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Mantooth, Marlo – Exam 1 – Due: Feb 2 2007, 1:00 pm – Inst: Donna C Lyon 1 This print-out should have 20 questions. Multiple-choice questions may continue on the next column or page – fnd all choices be±ore answering. The due time is Central time. 001 (part 1 o± 1) 10 points What is the weight-volume percent o± a solu- tion prepared by dissolving 9.00 g o± alcohol in enough water to make 30.0 mL o± solution? 1. 30.0% correct 2. 0.33% 3. 3.00% 4. 33.33% Explanation: m = 9.00 g V = 30.0 mL Percent is part/whole; in this case grams o± the solute (alcohol) over the volume o± the whole solution in mL: Percent = part whole × 100% = 9 . 00 g alcohol 30 . 0 mL soln × 100% = 30 . 0% 002 (part 1 o± 1) 10 points When making ice cream, salt (NaCl) is added to the water and ice mixture. The equilibrium temperature o± this ice-salt water mixture is 1. greater than 0 C because salt melts ice. 2. less than 0 C because salt has a very low specifc heat. 3. less than 0 C because salt reacts with water. 4. 0 C because it is at equilibrium. 5. greater than 0 C because NaCl melts at a higher temperature than water. 6. less than 0 C because the dissolved salt lowers the ±reezing point o± the ice/water mix- ture. correct Explanation: The equilibrium temperature o± a water- ice mixture is 0 C ( i.e. , the ±reezing point). When salt is added to the mixture, the ±reez- ing point ( i.e. , equilibrium temperature) is lowered. Salt does melt ice, but not by rais- ing its temperature, so don’t let that choice con±use you. Salt melts ice by lowering the ±reezing point. 003 (part 1 o± 1) 10 points Two aqueous solutions are separated by a membrane permeable only to water. Solution A is a 0.34 M KCl solution; and Solution B is a 0.64 M KCl solution. Which o± the ±ollowing statements is TRUE? 1. K + ions ²ow ±rom solution B to solution A. 2. H 2 O molecules ²ow ±rom solution A to solution B. correct 3. Pressure must be applied to solution A to create an equilibrium ²ow o± water molecules. 4. Cl - ions ²ow ±rom solution B to solution A. 5. For a reverse osmosis process, pressure must be applied to solution A. Explanation: Here the membrane is only permeable to water, so only H 2 O can pass ±rom solution A to solution B (or vice versa). As solution A is less concentrated than solution B, H 2 O molecules will spontaneously travel from so- lution A to solution B in order to make the concentrations o± the two solutions equal. 004 (part 1 o± 1) 10 points The phase diagram ±or a pure substance is given below.
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Mantooth, Marlo – Exam 1 – Due: Feb 2 2007, 1:00 pm – Inst: Donna C Lyon 2 Solid Liquid Vapor 50 100 150 200 250 300 100 200 300 400 Temperature, K Pressure,atm What is the lowest temperature at which liquid can exist? 1.
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EXAM 1 - Mantooth, Marlo Exam 1 Due: Feb 2 2007, 1:00 pm...

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