Final.Form A.BlueVersion.Answers.2008

Final.Form A.BlueVersion.Answers.2008 - Chem. 1B Final...

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1 Chem. 1B Final FORM A First letter of your last name: March 20, 2008 Name: Last Name First Name Perm # INSTRUCTIONS: No hats allowed. No sharing of calculators. Cell Phones, iPods, headsets, etc. must be turned off and put away. SCANTRON FORM: Use a PENCIL 1) Write your name 2) Bubble in FORM A 3) Bubble in your PERM number (7 digits only, no extra numbers) INFORMATION PAGE: An information page is provided separately. No other notes or books are allowed. There are 8 pages, 32 questions. Each question is worth 5 points. SHOW ALL YOUR WORK on the exam. Turn in the Scantron form and your Exam . 1. For a reaction, A B + C, Δ H = –30 kJ /mol and the activation energy, E a = 45 kJ /mol. What is the activation energy for the reverse reaction, B + C A? a) 75 kJ / mol b) 45 kJ / mol c) 15 kJ /mol ANSWERS are given on the last page d) 30 kJ / mol e) None of these 2. The decomposition of KClO 3 produces O 2 (g) according to the following reaction. K C l O 3 (s) KCl (s) + 3/2 O 2 (g) For the reaction, Δ H o = – 44.7 kJ and Δ S o = + 59.1 J/K. This reaction will be a) spontaneous at all temperatures b) spontaneous only when T > 756 K c) spontaneous only when T < 756 K d) nonspontaneous at all temperatures e) spontaneous only when T = 756 K
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2 3. Given the following data at 25 o C: CH 3 OH + 3/2 O 2 CO 2 + 2 H 2 O Δ H = – 726.6 kJ C (s, gr) + 1/2 O 2 CO Δ H = – 110.5 kJ C (s, gr) + O 2 CO 2 Δ H = – 393.5 kJ H 2 (g) + 1/2 O 2 H 2 O Δ H = – 285.8 kJ Calculate the Δ H for the following reaction. CO + 2 H 2 CH 3 OH a) + 157.8 kJ b) – 349.0 kJ c) + 128.0 kJ d) – 157.8 kJ e) – 128.0 kJ 4. Consider the following reaction at 25 o C and 1 atm. N 2 O 4 (g) 2 NO 2 (g) For this system at equilibrium, how will raising the temperature affect the amount of NO 2 present? a) The amount of NO 2 increases b) The amount of NO 2 decreases c) The amount of NO 2 stays the same d) More information is needed to answer this question. 5. For the combustion of ethene gas, C 2 H 4 ( g ), the standard enthalpy change, Δ H o = –1411.1 kJ/mol at 298 K. Given the following enthalpies of formation, calculate Δ H f ° for C 2 H 4 ( g ). Δ H f o (kJ /mol) CO 2 (g) – 393.5 H 2 O (l) – 285.9 a) + 52.3 kJ/mol b) – 52.3 kJ/mol c) + 731.7 kJ/mol d) – 731.7 kJ/mol e) – 2769.9. kJ/mol
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3 6. The enthalpy of vaporization for 1.00 mole of ethanol is 38.7 kJ/mol at its normal boiling point of 78 o C. Predict the sign or value of w, q, and Δ E when 1.00 mol of ethanol is vaporized reversibly at 78 o C and 1 atm.
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Final.Form A.BlueVersion.Answers.2008 - Chem. 1B Final...

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