Chemistry 301 Exam 4 - Barkley Thane Exam 4 Due Dec 6 2007...

Info icon This preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Barkley, Thane – Exam 4 – Due: Dec 6 2007, 11:00 pm – Inst: McCord 1 This print-out should have 26 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. The due time is Central time. McCord 11 AM ONLY ! ! ! ! 001 (part 1 of 1) 10 points The formation of solid calcium chloride from a gas of its ions is an endothermic process. 1. True 2. False correct Explanation: 002 (part 1 of 1) 10 points A process is thermodynamically reversible if 1. the final and initial states are the same. 2. The total entropy change is zero. correct 3. The heat and work are equal but opposite in sign. 4. the total entropy change is positive. 5. The heat is zero. Explanation: For a process to be reversible, it must re- sult in a total (universal) entropy change of zero. Then neither the forward nor the re- verse process results in decrease in the total entropy. 003 (part 1 of 1) 10 points Calculate the entropy of vaporization for com- pound X at its boiling point of 115 C. The enthalpy of vaporization of compound X is 34 . 3 kJ/mol. Correct answer: 88 . 3679 J / mol K. Explanation: Δ S = Δ H T T = 115 + 273.15 = 388 . 15 K Δ S = 34300 / 388 . 15 = 88 . 3679 J / mol K 004 (part 1 of 1) 10 points Find the standard enthalpy of formation for NH 3 (g) given N H bond enthalpy = 390 kJ · mol - 1 ; Δ H f H(g) = 217 . 9 kJ · mol - 1 ; Δ H f N(g) = 472 . 6 kJ · mol - 1 . 1. - 44 kJ · mol - 1 correct 2. - 83 kJ · mol - 1 3. - 1170 kJ · mol - 1 4. - 691 kJ · mol - 1 5. - 516 kJ · mol - 1 Explanation: 005 (part 1 of 1) 10 points A friend states that water freezing is a vio- lation of the second law of thermodynamics. Your best reply would be that 1. you must be thinking of the first law. 2. although the entropy of the water de- creases the entropy of the universe increased. correct 3. the second law does not apply at 0 C. 4. the second law does not apply to water. Explanation: The Second Law of Thermodynamics says that in spontaneous changes, the universe tends toward a state of greater disorder. 006 (part 1 of 1) 10 points Calorimetry can be used to find heats of com- bustion. Suppose a calorimeter helps some- one to determine that 4032 kJ of heat is re- leased during the combustion of 88.0 grams of propane, C 3 H 8 (44.0 g/mol). What would be the amount of heat released for the combus- tion of 0.500 moles of propane?
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Barkley, Thane – Exam 4 – Due: Dec 6 2007, 11:00 pm – Inst: McCord 2 1. 1008 kJ correct 2. 504 kJ 3. 2016 kJ 4. 4032 kJ 5. 8064 kJ Explanation: q = 4032 kJ m = 88.0 g n = 0.500 mol MW = 44.0 g/mol If we know how much heat is evolved from combusting 88 g of propane, then we can use the molecular weight of propane to calculate how much heat is evolved from the combus- tion of 0.5 moles: 4032 kJ 88 . 0 g C 3 H 8 44 . 0 g C 3 H 8 1 mol C 3 H 8 × 0 . 5 mol C 3 H 8 = 1008 kJ 007 (part 1 of 1) 10 points For the reaction H 2 (g) + Cl 2 (g) 2 HCl(g) at constant temperature and pressure, we would expect 1. Δ H Δ E .
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern