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Unformatted text preview: baum (awb464) H05: Bonding 1 Mccord (50970) 1 This print-out should have 25 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points Let X be a hypothetical element. Which of the following would be largest? 1. X 2. X- 3. X 2- correct 4. X + 5. X 2+ Explanation: X 2- would be largest as it has 2 more electrons than protons, and the protons here would be at the greatest disadvantage when trying to draw the electrons towards the nu- cleus. 002 10.0 points If the following crystallize in the same type of structure, which has the lowest lattice energy? 1. SrS 2. CaO 3. BaO 4. BaS correct 5. SrO Explanation: Lowest charge densities due to larger size. 003 10.0 points Use the expression for the Coulomb potential energy to calculate the energy for formation of 1 mole of sodium chloride ion-pairs; i.e. , the energy change for the reaction Na + (g) + Cl- (g) Na + Cl- (g) Assume the distance between the ions in the product is 283 pm. Correct answer:- 491 kJ / mol. Explanation: E = N A z 1 z 2 e 2 4 r 12 = (6 . 022 10 23 mol- 1 ) (+1) (- 1) 4 (8 . 85419 10- 12 J- 1 C 2 m- 1 ) (1 . 6022 10- 19 C) 2 2 . 83 10- 10 m =- 4 . 90941 10 5 J / mol =- 491 kJ / mol 004 10.0 points What is the crystal lattice energy of LiI? Sub- limation energy for Li is 155 kJ/mol and ion- ization energy for Li is 520 kJ/mol. Sublima- tion energy for I 2 is 62 kJ/mol and dissocia- tion energy for I 2 is 151 kJ/mol. The electron affinity for I is- 295 kJ/mol. The heat of formation for LiI(s) =- 271 kJ/mol. 1. +215.5 kJ/mol 2.- 215.5 kJ/mol 3. +726.5 kJ/mol 4.- 757.5 kJ/mol correct Explanation: 005 10.0 points In general, electronegativity tends to decrease 1. from bottom to top and from right to left on the periodic table. 2. in no regular trend. 3. from top to bottom and from right to left on the periodic table. correct 4. from bottom to top and from left to right on the periodic table. baum (awb464) H05: Bonding 1 Mccord (50970) 2 5. from top to bottom and from left to right on the periodic table. Explanation: Electronegativity generally increases from left to right and from bottom to top of the Periodic Table. 006 10.0 points Which of the following statements is true? 1. Atoms with low ionization energies and low electron affinities have high electronega- tivities. 2. The electronegativity of an atom depends only on the value of the ionization energy of the atom....
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This note was uploaded on 11/21/2010 for the course CHEM 50970 taught by Professor Dr.mccord during the Fall '10 term at University of Texas at Austin.
- Fall '10