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Final CH 301 - Version 245 Final quy(50970 This print-out...

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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 10.0points 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 10.0points 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 10.0points 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 10.0points 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
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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 10.0points 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 10.0points Which of the following is a true statement? 1. Weaker bonds have shorter bond lengths and lower bond orders. 2. Weaker bonds have longer bond lengths and higher bond orders. 3. Weaker bonds have longer bond lengths and lower bond orders. correct 4. Bond strength, bond length and bond order are not related. 5. Weaker bonds have shorter bond lengths and higher bond orders.
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