chemfinal - Version 006 Final Sutcliffe (53770) 1 This...

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Unformatted text preview: Version 006 Final Sutcliffe (53770) 1 This print-out should have 45 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. This exam is for Dr. Sutcliffes TTh section only. PLEASE double check all of your bub- bling carefully as we wont have much time to fix EID and version number errors afterwards. Good luck and have a great holiday! 001 10.0 points Consider the following compounds and their standard free energies of formation: cpd energy 1 C 6 H 12 ( ) 6.4 kJ mol 1 cyclohexane 2 CH 3 OH( )- 166 kJ mol 1 methanol 3 N 2 H 4 ( ) 149 kJ mol 1 hydrazine 4 H 2 O 2 ( )- 120 kJ mol 1 hydrogen peroxide 5 CS 2 ( ) 65.3 kJ mol 1 carbon disulfide Which of these liquids is/are thermody- namically unstable? 1. 2 and 3 only 2. 2 and 4 only 3. 1 and 4 only 4. 2 only 5. 1, 3, and 5 only correct Explanation: A thermodynamically unstable compound is one which has a positive value of G f . 002 10.0 points A hypothetical element has an atomic weight of 76 . 32 amu. The two isotopes of this element have mass numbers of 74 and 77. What is the percent abundance of the isotope with the mass number of 74? 1. 76 . 73% 2. 77 . 03% 3. 77 . 33% 4. 22 . 97% 5. 22 . 67% correct 6. 23 . 27% Explanation: 003 10.0 points Which one of the following statements is FALSE? 1. If heat absorbed for a process at con- stant pressure is negative, the process must be exothermic. 2. The work done in a process occuring at constant pressure is zero if n for gases is zero. 3. A bomb calorimeter measures H di- rectly. correct 4. The change in enthalpy for a process is equal to the amount of heat absorbed at con- stant pressure. 5. The change in internal energy for a pro- cess is equal to the amount of heat absorbed at constant volume. Explanation: A bomb calorimeter operates at constant volume. Therefore it measures q v , the amount of heat of heat given off or absorbed by a reaction occurring at constant volume. This quantity q v is E . 004 10.0 points Which statement is FALSE about B 2 ? 1. It is paramagnetic. 2. It has a bond order of 1. 3. It would be expected to have a longer bond length than C 2 . Version 006 Final Sutcliffe (53770) 2 4. It has two electrons in a 2 p orbital. cor- rect Explanation: 005 10.0 points At 80.0 C and 12.0 Torr, the density of cam- phor vapor is 0 . 0829 g L 1 . What is the molar mass of camphor? 1. 152 g mol 1 correct 2. 3490 g mol 1 3. 243 g mol 1 4. 20 . 3 g mol 1 5. 34 . 5 g mol 1 Explanation: T = 80 C + 273.15 K = 353.15 K P = (12 Torr) 1 atm 760 Torr = 0 . 0157895 atm = 0 . 0829 g/L The ideal gas law is P V = nRT n V = P RT with unit of measure mol/L on each side....
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This note was uploaded on 09/13/2011 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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chemfinal - Version 006 Final Sutcliffe (53770) 1 This...

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