CH 302 Exam 1 - Version 163 Exam 1 Sutclie(52440 This...

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Version 163 – Exam 1 – Sutclife – (52440) 1 This print-out should have 28 questions. Multiple-choice questions may continue on the next column or page – Fnd all choices be±ore answering. 001 10.0 points Colloids 1. do not exhibit the Tyndall efect. 2. have the ability to absorb light. 3. do not exhibit random molecular mo- tion. 4. have the ability to scatter light. correct Explanation: A characteristic property o± colloids, their ability to scatter light, is called the Tyndall efect. 002 10.0 points Many biological cells are killed i± they are placed in pure water because 1. the water in the cells passes out through the cell wall causing the cell to shrivel and die. 2. vital cell constituents dissolved in the cell ²uid pass through the cell wall causing the cells to die. 3. i± nothing can pass through the cell wall, the greater pressure inside than outside causes the cell to burst open. 4. more water passes in through the cell wall than passes out so the cells swell and burst. correct 5. i± nothing can pass through the cell wall, the greater pressure outside than inside causes the cell to collapse. Explanation: More solvent molecules pass through the semi-permeable cell membrance into the cell where the solvent concentration is low than in the other direction. This process coninues until pressure on both sides o± the membrane is equal or until the cell ±rom the large volume o± excess water that enters. 003 10.0 points Note this is looking ±or the CHANGE in VP ±rom that o± the pure solvent. What is the change in vapor pressure ±rom that o± pure water ±or an aqueous solution at 40 C in which the mole ±raction o± ±ructose is 0 . 38? The vapor pressure o± pure water at 40 C is 55 . 34 torr. 1. 18 . 93 torr 2. 25 . 24 torr 3. 23 . 13 torr 4. 21 . 03 torr correct 5. 16 . 82 torr 6. 14 . 72 torr Explanation: P pure solvent = 55 . 34 torr T = 40 χ fructose = 0 . 38 χ water = 1 - 0 . 38 = 0 . 62 P = χ solvent P pure solvent = 0 . 62(55 . 34 torr) = 34 . 3108 torr . The change in vapor pressure is Δ P = 55 . 34 torr - 34 . 3108 torr = 21 . 03 torr . 004 10.0 points Consider the phase diagrams ±or water and carbon dioxide. Explain the ±ollowing observations: A thin wire with weights attached is draped over a block o± “dry ice” and a second wire with weights is draped over a block o± ice. The wire cuts through the ice but not through the “ dry ice.”
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Version 163 – Exam 1 – Sutclife – (52440) 2 1. The melting point For water is reduced and For carbon dioxide increased with in- creased pressure. correct 2. The melting point For water is increased and For carbon dioxide reduced with increased pressure. 3. Both melting points are increased with increased pressure.
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This note was uploaded on 03/10/2011 for the course CH 302 taught by Professor Holcombe during the Spring '07 term at University of Texas.

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CH 302 Exam 1 - Version 163 Exam 1 Sutclie(52440 This...

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