exam4_solutions - Version 174 Exam 4 Sutcliffe (53770) 1...

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Unformatted text preview: Version 174 Exam 4 Sutcliffe (53770) 1 This print-out should have 25 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points Predict which of butane (C 4 H 10 ) or propanone (CH 3 COCH 3 ) has the greater vis- cosity. Assume that they are both at the same temperature and in their liquid form. 1. propanone correct 2. Equal viscosities 3. butane Explanation: Propanone ( a.k.a. acetone) should be more viscous than butane because it is more polar than butane. 002 10.0 points Which statement is FALSE? 1. H is equal to E for the process 2 H 2 (g) + O 2 (g) 2 H 2 O(g). correct 2. H is sometimes exactly equal to E . 3. H is often nearly equal to E . 4. The thermodynamic quantity most easily measured in a coffee cup calorimeter is H . 5. No work is done in a reaction occurring in a bomb calorimeter. Explanation: For 2 H 2 (g) + O 2 (g) 2 H 2 O(g) , n i = 3 mol gas n f = 2 mol gas n = 1 mol gas w = P V = ( n ) RT negationslash = 0 , Since E = q + w , q = H and w negationslash = 0, E negationslash = H . 003 10.0 points Which of the molecules H 2 , HF, CH 4 , CH 3 OH can be involved in hydrogen bonding? 1. CH 3 OH, CH 4 2. HF, CH 3 OH correct 3. CH 3 OH, H 2 4. HF, CH 4 Explanation: For a molecule to be involved in hydrogen bonding, the molecule must have a hydrogen atom and a highly electronegative atom such as F, O, N, or Cl. The only two molecules that satisfy these requirements are HF and CH 3 OH. 004 10.0 points Based on the information in the table, Species H f S kJ/mol J/mol K CHCl 3 ( ) 134 . 5 202 . CCl 4 ( ) 135 . 4 216 . 4 Cl 2 (g, 1 atm) . 223 . HCl (g, 1 atm) 92 . 31 186 . 8 what are H and S for the reaction CHCl 3 ( ) + Cl 2 (g, 1 atm) CCl 4 ( ) + HCl (g, 1 atm)? 1. H = +93 . 2 kJ/mol S = +82 . 8 J/mol K 2. H = 362.2 kJ/mol S = +82 . 8 J/mol K 3. H = 362.2 kJ/mol S = 21.8 J/mol K 4. H = 93.2 kJ/mol S = +21 . 8 J/mol K Version 174 Exam 4 Sutcliffe (53770) 2 5. H = 93.2 kJ/mol S = 21.8 J/mol K correct Explanation: H rxn = summationdisplay n H f prod summationdisplay n H f rct = [( 135 . 4 kJ / mol) +( 92 . 31 kJ / mol)] [( 134 . 5 kJ / mol)] = 93 . 21 kJ / mol rxn S rxn = summationdisplay nS f prod summationdisplay nS f rct = [216 . 4 J / mol K +186 . 8 J / mol K] [202 J / mol K +223 J / mol K] = 21 . 8 J / mol K 005 10.0 points When 2.00 kJ of energy is transferred as heat to nitrogen in a cylinder fitted with a piston at an external pressure of 2.00 atm, the nitro- gen gas expands from 2.00 to 5.00 L against this constant pressure. What is U for the process?...
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This note was uploaded on 09/09/2009 for the course CH 302 taught by Professor Mccord during the Spring '09 term at University of Texas-Tyler.

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exam4_solutions - Version 174 Exam 4 Sutcliffe (53770) 1...

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