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Unformatted text preview: sung (es24394) – Homework 2 – vanden bout – (51640) 1 This print-out should have 28 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points Both ammonia and phosphine (PH 3 ) are sol- uble in water. Which is least soluble and why? 1. ammonia; it is too small to be hydrated by water molecules. 2. ammonia; it does not form hydrogen bonds with water molecules. 3. phosphine; the P- H bonds are so strong that they cannot break to enable phosphine to hydrogen-bond with water. 4. phosphine; it does not form hydrogen bonds with water molecules. correct 5. ammonia; the N- H bonds are so strong that they cannot break to enable the ammonia to hydrogen-bond with water. Explanation: PH 3 is least soluble because it cannot form hydrogen bonds with water. 002 10.0 points Some distilled water is added to an empty beaker. A gram of copper(II) nitrate is added to the beaker with stirring. After a few min- utes, what is in the beaker? 1. nitrogen gas, copper atoms, electrons, and water 2. a sticky material of copper hydronitrite 3. solid copper(II) nitrate and water 4. solid copper, nitrate ions, and water 5. copper ions, nitrate ions, and water cor- rect Explanation: All nitrates are soluble in water, so the cop- per(II) nitrate dissolves. Soluble ionic com- pounds are strong electrolytes, so the cop- per(II) nitrate also dissociates into its cation and anion parts: Cu + 2 and NO − 3 . 003 10.0 points Which is the best representation of the solva- tion of a sodium cation in water? hydrogen oxygen Na + ion 1. 2. sung (es24394) – Homework 2 – vanden bout – (51640) 2 3. 4. correct Explanation: Since the water molecule has a partial neg- ative charge on the O atom, it will orient itself to the O atom closest to the positively charged cation. 004 10.0 points When we put sugar in water it melts. 1. False correct 2. True Explanation: Sugar dissolves in water and melts when its temperature is raised above its melting point. 005 10.0 points Rank the following in terms of decreas- ing miscibility in C 8 H 18 (octane): C 2 H 5 Cl (chloroethane), H 2 O (water), C 2 H 5 F (fluo- roethane), C 9 H 20 (nonane). 1. C 2 H 5 Cl > C 2 H 5 F > H 2 O > C 9 H 20 2. C 2 H 5 F > H 2 O > C 9 H 20 > C 2 H 5 Cl 3. H 2 O > C 9 H 20 > C 2 H 5 Cl > C 2 H 5 F 4. C 9 H 20 > C 2 H 5 Cl > C 2 H 5 F > H 2 O cor- rect Explanation: Octane is a non-polar solvent and thus ranking in terms of decreasing miscibility re- quires ranking in terms of decreasing non- polar character, i.e. from least to most polar. 006 10.0 points Octane (C 8 H 18 ) is a major component of gaso- line. Which of the following would you expect to be the LEAST soluble in gasoline?...
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This note was uploaded on 03/27/2011 for the course CHEM 302 taught by Professor Mccord during the Spring '10 term at University of Texas.
- Spring '10