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Unformatted text preview: enriquez (mne72) H02: Chapter 17 McCord (90262) 1 This print-out should have 29 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. A reminder that EXAM 1 is on Monday, August 20th, from 8:30 to 9:45 AM in WEL 2.224 - this is not our regular classroom, al- though it is next door. Bring a scientific cal- culator and your pencil for the exam. Please skip at least one seat between each student. 001 10.0 points Dissociation of a solid is aided by 1. strong interaction between solvent molecules. 2. strong binding in the solid and weak solvent-solute interaction. 3. weak binding of species in the solid and strong interactions between the solvent and solute. correct 4. None of these is correct. Explanation: Weak intermolecular forces in the solute facilitate separation of its particles and strong attractive forces between solute and solvent facilitate dissociation of a solid. 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, nitrate ions, and water 4. copper ions, nitrate ions, and water cor- rect 5. solid copper(II) nitrate and water 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 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. phosphine; it does not form hydrogen bonds with water molecules. correct 3. phosphine; the P- H bonds are so strong that they cannot break to enable phosphine to hydrogen-bond with water. 4. ammonia; the N- H bonds are so strong that they cannot break to enable the ammonia to hydrogen-bond with water. 5. ammonia; it does not form hydrogen bonds with water molecules. Explanation: PH 3 is least soluble because it cannot form hydrogen bonds with water. 004 10.0 points Water causes many electrolytes to dissociate 1. because it undergoes hydrogen bonding to large halide ions. 2. because the dispersion forces between ion and solvent are strong. 3. because water molecules are dipoles and the dipoles orient in an energetically favorable manner to solvate the ions. correct 4. because of repulsive interactions between ions in the crystalline state. Explanation: The more negative end of the water enriquez (mne72) H02: Chapter 17 McCord (90262) 2 molecule orients toward the cation and the more positive end orients toward the anion; the ions remain apart....
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