HW3 solutions - Byers, Raymond – Homework 3 – Due: Feb...

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Unformatted text preview: 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 – find all choices before answering. The due time is Central time. 001 (part 1 of 1) 10 points Several interesting observations from the world around you are listed below. Which of these is NOT explained by a col- ligative property? 1. Water boils at a higher temperature when salt is added. 2. The freezing point of water is lowered when salt is added. 3. A lobster will die when placed in fresh water. 4. At high altitude it takes longer to cook spaghetti. correct 5. Antifreeze is added to a car radiator to keep the car from overheating. Explanation: Colligative properties of a solution depend on the number of 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 of 1) 10 points Which of the following statements about col- ligative properties of aqueous solutions is FALSE? 1. Osmosis is a colligative property. 2. The higher the concentration of solute in the solution, the higher the vapor pressure of the solvent. correct 3. Colligative properties only depend on the number of solute particles present in solu- tion. 4. For a given solution, the freezing 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 of solute particles present in solution, not on their properties. The effect on the melting point of a given solution is less than the effect on its boiling point. With a higher concentration of non-volatile solute the concentration of the solvent in the solution is lower, causing the vapor pressure of the solution to be lower. 003 (part 1 of 1) 10 points Which of the following 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 of 1) 10 points Which of the following 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 of 1) 10 points Calculate the number of moles of oxygen that will dissolve in 45 L of water at 20 ◦ C if the par- 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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This note was uploaded on 02/23/2010 for the course CH 302 taught by Professor Holcombe during the Fall '07 term at University of Texas.

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HW3 solutions - Byers, Raymond – Homework 3 – Due: Feb...

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