Final CH 301 - Version 245 – Final – quy –(50970 1 This print-out should have 48 questions Multiple-choice questions may continue on the next

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Unformatted text preview: Version 245 – Final – quy – (50970) 1 This print-out should have 48 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points Which of the following species is paramag- netic? 1. Be 2 − 2 correct 2. N 2 3. He 2 4. C 2 − 2 Explanation: The species Be 2 − 2 will have two unpaired electrons in degenerate π bonding orbitals. 002 10.0 points Which of the following gases would diffuse most rapidly? 1. He correct 2. CH 4 3. N 2 4. O 2 5. CO 2 Explanation: Because they remove faster, light gas molecules diffuse and effuse faster than heav- ier ones. 003 10.0 points The ions Na + , F − , and O 2 − each have ten electrons. What would be the order of the sizes of these three ions? 1. Na + is smaller than F − which is smaller than O 2 − . correct 2. Na + is smaller than O 2 − which is smaller than F − . 3. F − is smaller than O 2 − which is smaller than Na + . 4. O 2 − is smaller than Na + which is smaller than F − . 5. F − is smaller than Na + which is smaller than O 2 − . Explanation: Positive ions tend to be smaller than nega- tive ions because they have fewer electrons and the remaining electrons experience a larger effective nuclear charge. Negative ions, on the other hand, have extra electrons, each of which experiences a lower effective nuclear charge. The more extra electrons an ion has, the larger it will be within a row, and the more electrons an ion loses, the smaller the ion within a row. Atomic radii and ionic radii both increase as you move down a col- umn since the electrons are in higher energy orbitals and further away from the nucleus. 004 10.0 points The following reaction occurs during the pro- duction of metallic iron: 2 Fe 2 O 3 (s) + 3 C(graphite) → 4 Fe(s) + 3 CO 2 (g) Calculate Δ H for this reaction at 25 ◦ C and 1 atm. Δ H f for CO 2 (g) =- 393 . 51 kJ/mol, and Δ H f for Fe 2 O 3 (s) =- 824 . 2 kJ/mol. 1. +430.7 kJ 2. There is insufficient information to answer this question. 3.- 430.7 kJ 4. +467.9 kJ correct 5.- 467.9 kJ Explanation: Δ H rxn = Δ H products- Δ H reactants Version 245 – Final – quy – (50970) 2 = (- 393 . 51)(3)- (- 824 . 2)(2) = 467 . 9 kJ Note : The enthalpy of a pure element is al- ways zero. 005 10.0 points Which of the following is the strongest inter- molecular force between molecules? 1. ion-dipole 2. London 3. dipole-dipole (rotating) 4. dipole-dipole (stationary) 5. hydrogen bonding correct Explanation: In general, the strongest intermolecular force is hydrogen bonding. 006 10.0 points Which of the following is a true statement? 1. Weaker bonds have shorter bond lengths and lower bond orders....
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This note was uploaded on 12/08/2011 for the course CH 301 taught by Professor Fakhreddine/lyon during the Fall '07 term at University of Texas at Austin.

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Final CH 301 - Version 245 – Final – quy –(50970 1 This print-out should have 48 questions Multiple-choice questions may continue on the next

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