Exam 4 - Version 083 Exam Four: Shear Shear (52375) 1 This...

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Unformatted text preview: Version 083 Exam Four: Shear Shear (52375) 1 This print-out should have 25 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. DrRuth says: In all cases, select the answer that BEST answers the question asked. The total points on this exam is 300, and it counts equally with all previous inclass exams. Read the whole thing first and plan which to answer first because you feel confident about them. Notice the harder ones and save them up till last so you dont use up all your time working on them. Shear 52375 1 L atm = 101.325 J 1 cal = 4.184 J R = see back of scantron sheet 001 25.0 points Given the following data: Fe 2 O 3 (s) + 3CO(g) 2Fe(s) + 3CO 2 (g) H =- 23 kJ mol 1 3Fe 2 O 3 (s) + CO(g) 2Fe 3 O 4 (s) + CO 2 (g) H =- 39 kJ mol 1 Fe 3 O 4 (s) + CO(g) 3FeO(s) + CO 2 (g) H = 18 kJ mol 1 calculate H for the reaction FeO(s) + CO(g) Fe(s) + CO 2 (g) 1.- 2 kJ mol 1 2.- 66 kJ mol 1 3.- 11 kJ mol 1 correct 4.- 18 . 5 kJ mol 1 5.- 13 . 5 kJ mol 1 Explanation: H rxn = 1 2 (- 23 kJ mol 1 )- 1 6 (- 39 kJ mol 1 )- 1 3 (18 kJ mol 1 ) =- 11 kJ mol 1 002 10.0 points Which of the compounds I) PCl 5 (g); II) NO(g); III) HCN(g); IV) SO 2 (g); is/are unstable and will decompose into their elements under standard conditions at 25 C? H f S G f ( kJ mol ) ( J K mol ) ( kJ mol ) PCl 5 (g)- 374 . 9 364.6- 305 . NO(g) 90.25 210.76 86.55 HCN(g) 135.1 201.78 124.7 SO 2 (g)- 296 . 83 248.22- 300 . 19 1. Another combination 2. II, III, and IV only 3. III only 4. Cannot be determined 5. I and III only 6. II and IV only 7. I, II and IV only 8. II and III only correct 9. I, II and III only 10. I only Explanation: Examine the standard free energies of for- mation of the compounds. Compounds with a negative free energy of formation are stable, whereas those with a positive free energy are unstable with respect to the elements that compose them. Accord- ingly, only SO 2 and PCl 5 (g) are thermody- namically stable while HCN(g) and NO(g) are unstable. Version 083 Exam Four: Shear Shear (52375) 2 003 10.0 points The heat of combustion of butane (C 4 H 10 ) is- 2878 kJ/mol. Assume a typical cigarette lighter holds about 1.75 g of butane. How much heat energy would be released if ALL of the butane in the lighter were combusted? 1. 40.61 kJ 2. 86.63 kJ correct 3. 95.59 kJ 4. 1.05 kJ Explanation: MW butane = 58.14 g/mol ? kJ =- 2878 kJ mol (1 . 75 g) 1 mol 58 . 14 g =- 86 . 6271 kJ 004 10.0 points The following reaction 2 Cu(s) + CO 2 (g) 2 CuO(s) + C(s) is endothermic. Which statement is true?...
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This note was uploaded on 11/08/2010 for the course CHEM 301 taught by Professor Wandelt during the Spring '08 term at University of Texas at Austin.

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Exam 4 - Version 083 Exam Four: Shear Shear (52375) 1 This...

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