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HW5S - Gauthier Joseph Homework 5 Due Oct 2 2007 midnight...

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Gauthier, Joseph – Homework 5 – Due: Oct 2 2007, midnight – Inst: Vandenbout 1 This print-out should have 26 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 Which of the following pairs of ions would have the greatest coulombic attraction in a solid compound? 1. Mg 2+ , Se 2 - 2. Mg 2+ , O 2 - correct 3. Mg 2+ , S 2 - Explanation: E 1 r , so the ion with the shortest radius will have the greatest coulombic attraction. 002 (part 1 of 1) 10 points An element E has the electronic configuration [Ne] 3 s 2 3 p 1 . Write the formula of its com- pound with sulfate. 1. E 2 (SO 4 ) 3 correct 2. E(SO 4 ) 3 3. E 3 (SO 4 ) 2 4. E 2 (SO 4 ) 5. E 3 (SO 4 ) 6. E(SO 4 ) 2 Explanation: E is aluminum; since it has three valence electrons it forms a +3 ion isoelectronic with Ne. 003 (part 1 of 1) 10 points Use electron-dot notation to demonstrate the formation of ionic compounds involving the elements Ca and I. 1. Ca + I -→ Ca + + I - -→ CaI 2. Ca + Ca + I + I + I -→ Ca 3+ +Ca 3+ + I 2 - + I 2 - + I 2 - -→ Ca 2 I 3 3. None of these 4. Ca + Ca + Ca + I + I -→ Ca 2+ +Ca 2+ +Ca 2+ + I 3 - + I 3 - -→ Ca 3 I 2 5. Ca + Ca + I -→ Ca + + Ca + + I 2 - -→ Ca 2 I 6. Ca + I -→ Ca 2+ + I 2 - -→ CaI 7. Ca + Ca + Ca + I -→ Ca + + Ca + + Ca + + I 3 - -→ Ca 3 I 8. Ca + I + I + I -→ Ca 3+ + I - + I - + I - -→ Ca 2 I 3 9. Ca + I + I -→ Ca 2+ + I - + I - -→ CaI 2 correct 10. Ca + I -→ Ca 3+ + I 3 - -→ CaI Explanation: Ca gives up two electrons to form the Ca 2+
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Gauthier, Joseph – Homework 5 – Due: Oct 2 2007, midnight – Inst: Vandenbout 2 cation, and I acquires an electron to form the I - anion. Two iodine anions combine with one cal- cium cation to form an electrically neutral compound: Ca + I + I -→ Ca 2+ + I - + I - -→ CaI 2 004 (part 1 of 1) 10 points Which of the compounds below has bonds with the most covalent character? 1. CaCl 2 2. BeCl 2 correct 3. LiCl 4. NaCl 5. MgCl 2 Explanation: ΔEN is min for BeCl 2 . 005 (part 1 of 1) 10 points The lattice enthalpy of calcium bromide is the energy change for the reaction 1. Ca(s) + Br 2 ( ) CaBr 2 (s) 2. CaBr 2 (s) Ca(g) + 2 Br(g) 3. Ca(g) + 2 Br(g) CaBr 2 (g) 4. CaBr 2 (s) Ca 2+ (g) + 2 Br - (g) correct 5. CaBr 2 (s) Ca(g) + Br 2 (g) Explanation: 006 (part 1 of 1) 10 points How many valence electrons are in a S atom? 1. 2 2. 4 3. 16 4. 6 correct 5. 8 Explanation: Valence electrons are electrons that are found in the outermost energy levels of an atom. For S, Atomic number : 16 Electronic configuration : [Ne] 3 s 2 3 p 4 Shell Structure : 2 - 8 - 6 Therefore, S has 6 valence electrons. 007 (part 1 of 1) 10 points The P 2 - anion has how many total electrons and how many valence electrons? 1. 16; 7 2. 17; 8 3. 15; 5 4. 16; 5 5. 18; 8 6. 16; 6 7. 17; 7 correct 8. 15; 6 9. 17; 6 10. 15; 7 Explanation: P 2 - has gained 2 electrons to give it a total of 17. In its valence, it has 3 s 2 3 p 5 , giving it a total of 7 valence electrons.
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