Chemistry 1A, Fall 2010 Midterm Exam #3 November 10, 2010 (90 min, closed book) Name:__________________________________ SID:___________________________________ GSI Name:________________ x The test consists of 5 short answer questions and 21 multiple choice questions. x Put your written answers in the boxes provided. Answers outside the boxes may not be considered in grading. x Write your name on every page of the exam. Question Page Points Score Multiple Choice 2-7 77 Bond Energy 4 13 CO 2 Capture 5 5 Etching Copper 6 5 Total 100 Useful Equations and constants: ' G q = ' H q - T ' S q ' H q = 6 n ' H q f (products) - 6 n ' H q f (reactants) ' S q = 6 nS q (products) - 6 nS q (reactants) ' G q = 6 n ' G q f (products) - 6 n ' G q f (reactants) S = k B lnW ' S = q rev /T ' E = q + w w = - P ext ' V ' G q = - RTln K ' G = ' G q + RTln Q ' G q = - nF ' Eº ' E = ' Eº - (RT/nF) lnQ q = n C p ' T N 0 = 6.02214 ×10 23 mol -1 T (K) = T (C) + 273.15 F = 96,485 C mol -1 1 V = 1 J C -1 R = 8.31451 J K -1 mol -1 R = 8.20578 × 10 -2 L atm K -1 mol -1 A
Name_____________________GSI__________ CCCCHHHHHCHH+ H2HHHethylcyclopropaneCCCCpentaneHHHHHHHHCHHHHBREAKING AND MAKING BONDS Consider the following reactions of hydrogen gas with C5H10. The ǻHrxn° can be predicted from either enthalpy of formation data or bond energy data. The ǻHrxn° calculated from ǻHf° are shown below. Reaction #1 ǻHrxn° = í68 kJ/mol Reaction #2 ǻHrxn° = í148 kJ/mol 1.Which statement is true about Reaction #1 and Reaction #2? Page 2 of 8 A) For both reactions, energy is required to break 1 H-H and 1 C-C bond. B) For both reactions, energy is released when 2 C-H bonds form. C) Both reactants have the same molecular formula. D) All of the above are true statements 2.ǻHf° (pentane) is í168 kJ/mol. What is ǻHf° for ethylcyclopropane?
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