final solutions - Kim, Siwon Final 1 Due: Dec 12 2007,...

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Unformatted text preview: Kim, Siwon Final 1 Due: Dec 12 2007, 11:00 pm Inst: Donna C Lyon 1 This print-out should have 50 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 The Lewis dot structure for an isolated phos- phorous atom has 1. four pairs of electrons. 2. one pair of electrons and three lone elec- trons. 3. two pairs of electrons and one lone elec- tron. correct 4. five lone electrons. 5. three pairs of electrons and one lone elec- tron. Explanation: 002 (part 1 of 1) 10 points Calculate the enthalpy change per mole for the reaction O 2 (g) 2 3 O 3 (g) , given the following: H (kJ/mol rxn) C(s) + O 2 (g) CO 2 (g)- 394 3C(s) + 2O 3 (g) 3CO 2 (g)- 1611 1.- 537 kJ/mol 2. +1217 kJ/mol 3. +143 kJ/mol correct 4. +95 kJ/mol 5.- 1217 kJ/mol Explanation: Reaction H f (kJ / mol) C + O 2 CO 2- 394 1 3 h 3 CO 2 3 C + 2 O 3 i 1 3 (1611) O 2 2 3 O 3 143 Total heat produced = +143 kJ mol 003 (part 1 of 1) 10 points The photoelectric effect is a result of the 1. particle nature of electrons. 2. wave nature of light. 3. consistency of the electromagnetic spec- trum. 4. wave nature of electrons. 5. particle nature of light. correct Explanation: When electromagnetic radiation (light) of sufficient minimum energy strikes a metal cathode, electrons are knocked off its sur- face, travel to an anode, and form a current through a circuit. Two important observations were: 1) Electrons can be ejected only if the light is sufficiently energetic. Electron ejection is independent of time or intensity. The mini- mum energy varies by element. 2) The current increases with increasing intensity and is independent of color. Therefore, light is made up of photons, each having a particular amount of energy that can be transferred to an electron during a colli- sion. If the energy is equal to or greater than the amount needed to liberate the electron, it can escape to join the photoelectric current. Intensity is the number of photons hitting a surface per unit time. 004 (part 1 of 1) 10 points Calculate G at 298 K for the reaction 2Ag 2 O(s) 4Ag(s) + O 2 (g) . Kim, Siwon Final 1 Due: Dec 12 2007, 11:00 pm Inst: Donna C Lyon 2 Species H f S kJ/mol J/mol K Ag(s) . 42 . 55 Ag 2 O(s)- 30 . 57 121 . 7 O 2 (g) . 205 . 1.- 69.85 kJ/mol rxn 2. 52.7 kJ/mol rxn 3. 21.9 kJ/mol rxn correct 4. 81.2 kJ/mol rxn 5. 38.2 kJ/mol rxn Explanation: H rxn = X n H f prod- X n H f rct = 0 kJ / mol- 2(- 30 . 57 kJ / mol) = 61 . 14 kJ / mol S rxn = X n S f prod- X n S f rct = h 4(42 . 55 J / mol K) +(205 . 0 J / mol K) i- 2(121 . 7 J / mol K) = 131 . 8 J / mol K kJ 1000 J = 0 . 1318 kJ / mol K G = H- T S = (+61 . 14 kJ / mol)- (298 K)(0 . 1318 kJ / mol K) = 21 . 8636 kJ / mol rxn 005 (part 1 of 1) 10 points Is n = 5, =- 3, m =- 2, m s = + 1 2 a valid set of quantum numbers?...
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final solutions - Kim, Siwon Final 1 Due: Dec 12 2007,...

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