HW3 solutions

# HW3 solutions - Byers Raymond Homework 3 Due Feb 6 2006...

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Byers, Raymond – Homework 3 – Due: Feb 6 2006, noon – Inst: J A Holcombe 1 This print-out should have 22 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 Several interesting observations ±rom the world around you are listed below. Which o± these is NOT explained by a col- ligative property? 1. Water boils at a higher temperature when salt is added. 2. The ±reezing point o± water is lowered when salt is added. 3. A lobster will die when placed in ±resh water. 4. At high altitude it takes longer to cook spaghetti. correct 5. Anti±reeze is added to a car radiator to keep the car ±rom overheating. Explanation: Colligative properties o± a solution depend on the number o± solute particles in solution, not the type. Boiling point variations due to pressure changes have nothing to do with solutions and colligative properties (boiling point variations due to particles in solution, etc.). 002 (part 1 o± 1) 10 points Which o± the ±ollowing statements about col- ligative properties o± aqueous solutions is FALSE? 1. Osmosis is a colligative property. 2. The higher the concentration o± solute in the solution, the higher the vapor pressure o± the solvent. correct 3. Colligative properties only depend on the number o± solute particles present in solu- tion. 4. For a given solution, the ±reezing point will be lowered more than the boiling point will be raised. Explanation: Colligative properties, which include osmo- sis, vapor pressure lowering, melting and boil- ing point elevations, depend only on the num- ber o± solute particles present in solution, not on their properties. The e²ect on the melting point o± a given solution is less than the e²ect on its boiling point. With a higher concentration o± non-volatile solute the concentration o± the solvent in the solution is lower, causing the vapor pressure o± the solution to be lower. 003 (part 1 o± 1) 10 points Which o± the ±ollowing would likely dissolve in benzene? 1. C 6 H 12 O 6 2. Ca(HCO 3 ) 2 3. Cl 2 CCCl 2 correct 4. Na 2 CO 3 5. NaCl Explanation: 004 (part 1 o± 1) 10 points Which o± the ±ollowing solutes is likely to be most soluble in water? 1. carbon tetrachloride (CCl 4 ) 2. ethanol (CH 3 CH 2 OH) correct 3. CS 2 4. Br 2 Explanation: 005 (part 1 o± 1) 10 points Calculate the number o± moles o± oxygen that will dissolve in 45 L o± water at 20 C i± the par-

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Byers, Raymond – Homework 3 – Due: Feb 6 2006, noon – Inst: J A Holcombe 2 tial pressure of oxygen is 0.21 atm. Henry’s constant for oxygen is 0.0013 mol L · atm . 1. 0.28 mol 2. 0.0013 mol 3. 0.0062 mol 4. 0.00027 mol 5. 0.012 mol correct Explanation: 006 (part 1 of 1) 10 points Calculate the molality of perchloric acid in 9.2 M HClO 4 (aq). The density of this solution is 1.54 g/mL.
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HW3 solutions - Byers Raymond Homework 3 Due Feb 6 2006...

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