Homework 04 - Su Yung – Homework 4 – Due 11:00 pm – Inst FAKHREDDINE 1 This print-out should have 42 questions Multiple-choice questions may

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Unformatted text preview: Su, Yung – Homework 4 – Due: Oct 10 2007, 11:00 pm – Inst: FAKHREDDINE 1 This print-out should have 42 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. The due time is Central time. Each question is worth one point. 001 (part 1 of 1) 1 points What is the crystal lattice energy of KI? Sub- limation energy for K is 90 kJ/mol and ion- ization energy for K is 419 kJ/mol. The sub- limation energy for I 2 is 62 kJ/mole and the dissociation energy for I 2 is 151 kJ/mol. The electron affinity for I is- 295 kJ/mo and the heat of formation for KI(s) is- 328 kJ/mol. 1.- 693 kJ/mol 2.- 649 kJ/mol correct 3.- 755 kJ/mol 4.- 549 kJ/mol Explanation: 002 (part 1 of 1) 1 points Which one of the following pairs of elements would be expected to form an ionic com- pound? 1. As, Br 2. Rb, Cl correct 3. C, I 4. H, C 5. S, F Explanation: Metals and nonmetals react to form ionic compounds. Nonmetals and nonmetals react to form covalent compounds. Rb is a metal and Cl is a nonmetal, so they will form an ionic compound. S, F, H, C, As, Br, and I are all nonmetals. 003 (part 1 of 1) 1 points Which of the following is the best represen- tation of the compound magnesium oxide? 1. Mg 2+ , 2 • O ‚- 2. 2Mg + , • O ‚ 2- 3. Mg + , • O ‚- 4. 3Mg 2+ , 2 • O ‚ 3- 5. None is appropriate because magnesium oxide is a covalent compound. 6. Mg 2+ , • O ‚ 2- correct Explanation: Thebestdrawingwillshowthevalenceelec- trons, the charges, and the appropriate ratio of ions for MgO. 004 (part 1 of 1) 1 points Which of the following would have the highest melting point? 1. RbF 2. KCl 3. KBr 4. KF correct 5. KI Explanation: KF has the highest charge density. 005 (part 1 of 1) 1 points Which one of the following substances would be expected to have the highest melting point? 1. hydrogen fluoride (HF) 2. boron trifluoride (BF 3 ) Su, Yung – Homework 4 – Due: Oct 10 2007, 11:00 pm – Inst: FAKHREDDINE 2 3. methane (CH 4 ) 4. water (H 2 O) 5. sodium fluoride (NaF) correct Explanation: 006 (part 1 of 1) 1 points The formation of ionic solids from the ele- ments is an exothermic process. This is pri- marily due to 1. the low values for ionization of the met- als. 2. the large values of electronegativities of the atoms. 3. the electron affinity term. 4. the low values for vaporization of the metals. 5. the large magnitude of the lattice energy values of these solids. correct Explanation: 007 (part 1 of 1) 1 points In one mole of the compound lithium sulfide, what fraction of the total number of ions is S 2- ions? 1. 1 2 2. 1 3 correct 3. 1 4 4. None of the other answers is correct. 5. 2 3 Explanation: A lithium ion has a charge of +1. A sul- fide ion has a charge of- 2. The formula for lithium sulfide is Li 2 S, so each formula unit of lithium sulfide contains two lithium ions and one sulfide ion. One of every three ions is a sulfide ion, making the fraction of sul- fide ions 1 3 . This fraction will hold true for....
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This note was uploaded on 04/15/2009 for the course CH 54740 taught by Professor Fakhreddine during the Spring '09 term at University of Texas at Austin.

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Homework 04 - Su Yung – Homework 4 – Due 11:00 pm – Inst FAKHREDDINE 1 This print-out should have 42 questions Multiple-choice questions may

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