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Unformatted text preview: Anderson, Kiel Homework 2 Due: Feb 2 2007, midnight Inst: McCord 1 This print-out should have 18 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 For which of the following ions would the hydration process give off the least heat? 1. Ba +2 2. Li + 3. K + correct 4. Al 3+ 5. Mg +2 Explanation: A small charge-to-radius ratio means that the hydration process will give off a small amount of heat. This term is smallest for K + . 002 (part 1 of 1) 10 points The change in energy accompanying the (hy- pothetical) process M + (g) + X- (g) MX(s) is the ? of MX. 1. heat of hydration 2. crystal lattice energy correct 3. heat of ionization 4. heat of dissociation 5. heat of solution Explanation: The crystal lattice energy is the energy change accompanying the formation of one mole of formula units in the crystalline state from constituent particles in the gaseous state. It is always exothermic; i.e. , crystal lattice energies are always negative . 003 (part 1 of 1) 10 points Dissociation of a solid is aided by 1. strong interaction between solvent molecules. 2. None of these is correct. 3. weak binding of species in the solid and strong interactions between the solvent and solute. correct 4. strong binding in the solid and weak solvent-solute interaction. 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. 004 (part 1 of 1) 10 points A colligative property of a solution is one that depends 1. on the identity of the solute and the con- centration of the solution. 2. only on the identity of the solute. 3. only on the identity of the solvent. 4. only on the concentration of the solu- tion. 5. on the identity of the solvent and the concentration of the solution. correct Explanation: A colligative property depends on the con- centration of solution but NOT the identity of the solute. It does depend on the identity of solvent because substances have different solubilities depending on the solvent. 005 (part 1 of 1) 10 points The vapor pressure of pure CH 2 Cl 2 (with molecular weight 85 g/mol) is 133 torr at C and the vapor pressure of pure CH 2 Br 2 (with molecular weight 174 g/mol) is 11 torr Anderson, Kiel Homework 2 Due: Feb 2 2007, midnight Inst: McCord 2 at the same temperature. What is the total vapor pressure at 0 C of a solution prepared from equal masses of these two substances?...
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- Spring '07