2 - Elbel, Brittany Homework 2 Due: Jan 30 2006, noon Inst:...

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Unformatted text preview: Elbel, Brittany Homework 2 Due: Jan 30 2006, noon Inst: J A Holcombe 1 This print-out should have 19 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. The due time is Central time. The grading on homework has been changed to allow more than one guess. Good luck! 001 (part 1 of 1) 10 points Calculate G r for the decomposition of mer- cury(II) oxide 2HgO(s) 2Hg( ) + O 2 (g) H f- 90 . 83-- (kJ mol- 1 ) S m 70 . 29 76 . 02 205 . 14 (J K- 1 mol- 1 ) at 298 K. 1.- 246.2 kJ mol- 1 2.- 64.5 kJ mol- 1 3. +246.2 kJ mol- 1 4. +117.1 kJ mol- 1 correct 5.- 117.1 kJ mol- 1 Explanation: 002 (part 1 of 1) 10 points The standard free energy of formation of CS 2 ( ) is 65.27 kJ mol- 1 at 298 K. This means that at 298 K 1. CS 2 ( ) has a negative entropy. 2. CS 2 ( ) is thermodynamically unstable. correct 3. CS 2 ( ) is thermodynamically stable. 4. CS 2 ( ) will not spontaneously form C(s) + 2S(s). 5. No catalyst can be found to decompose CS 2 ( ) into its elements. Explanation: 003 (part 1 of 1) 10 points Consider the following reaction: CO(g) + Cl 2 (g) COCl 2 (g) Species H f S kJ/mol J/mol K CO- 110 . 5 197 . 6 Cl 2 . 223 . COCl 2- 223 . 289 . 2 Calculate G for the reactions at 298 K. 1.- 73 . 34 kJ/mol correct 2.- 500 . 0 kJ/mol 3.- 7 . 3 J/mol 4. 221 . 1 kJ/mol Explanation: 004 (part 1 of 1) 10 points A thermodynamically favorable reaction 1. if also kinetically favorable, proceeds at a detectable rate. 2. is called spontaneous but doesnt neces- sarily proceed at a detectable rate. 3. All choices are correct. correct 4. has negative G . Explanation: A reaction is spontaneous (favorable) when G is negative. Just because a reaction is thermodynamically favorable doesnt mean that it proceeds fast enough to be detected. Only when a reaction is kinetically favorable can it be detected....
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2 - Elbel, Brittany Homework 2 Due: Jan 30 2006, noon Inst:...

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