Midterm1_02_08 - Comments on this midterm: - I provide an...

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Unformatted text preview: Comments on this midterm: - I provide an extensive formula sheet with every exam. I believe that it is still necessary to understand the formulas, though! - This midterm may have been a bit too long for the time frame of 50 minutes. - There is a psychological problem – if you want to call it that – with posting old exams: Invariably, the new exam will look more difficult than the ones from previous years, whether or not it really is more difficult! The reason is that of the very different situation – doing the old test at home in a stress-free environment is very different from an actual exam situation. I want you to be aware of this … _____________________________________________________________________________ UNIVERSITY OF MANITOBA, DEPARTMENT OF CHEMISTRY Chemistry 2290, Winter 2008, Dr. H. Georg Schreckenbach First Midterm Examination February 11, 2008 Make sure the exam has 4 (four) pages. READ the question carefully! Answer ALL questions. The only exceptions are questions 1d and 3c that are marked 'Bonusʼ: These particular questions are optional but may earn you extra points. All questions have multiple parts. Note that the questions arenʼt necessarily ordered by difficulty. If you use pencil, your exam will not be remarked! For numerical problems, all mathematical steps must be shown. Please answer all questions on the question sheets. Use reverse side or extra paper if more space is needed. On any extra sheet, indicate your name and student ID number, please. _____________________________________________________________________________ 1. Laws of Thermodynamics 3 marks (a-c); 1 bonus mark (d) (a) Give a concise verbal statement of the Zeroth Law of Thermodynamics. (b) What if any is the connection between the Zeroth Law of Thermodynamics and the temperature? (c) Give a concise verbal statement of the First Law of Thermodynamics that contains the words “state function”. (d Bonus) Provide a brief formal proof that your formulation in part (c) is equivalent to a formulation of the First Law that concerns a Perpetuum Mobile machine. 2. More on concepts 4 marks (a) In the context of thermodynamics, what is a state function? (Definition.) (b) Is the heat capacity a state function? (Yes/ No) (c) What is the connection between the fact that the entropy is a state function and the concept of “reversibility”? 3. Van der Waals equation of State for Gases 2 marks (a–b); 1 bonus mark (c) The figure to the right shows isotherms for the van der Waals equation of state (temperature and pressure normalized to some critical values TC and pC, respectively; figure copied from Atkins, de Paula, Physical Chemistry, 8th ed.) [I showed figure 1.18 from Atkins.] (a) What is an isotherm? (Definition) Chemistry 2290 Midterm Examination 1, Winter 2008 1 (b) In the diagram, mark region(s) where the ideal gas law applies approximately. (c Bonus) Show mathematically how, under certain conditions (as per question b), the van der Waals equation transforms into the ideal gas equation of state. 4. First Law and Second Laws 11 marks Consider 3.00 mol water vapor at constant atmospheric pressure (1.00atm) that is initially at 123.0ºC. The vapor is (i) cooled to 100.0ºC and subsequently (ii) condensated to liquid water at that same temperature of 100.0ºC. (a) For steps (i) and (ii) of this overall process, calculate in each case the work w and heat q, as well as ΔU, ΔH and ΔS of the system. Assume that the vapor behaves as an ideal gas (even though this assumption might be somewhat problematic!) (b) What can you say about ΔSSurr? For this question you may need (some of) the following information: ΔHm(vaporization) = 40.656 kJ mol-1 (at atmospheric pressure and 373.15K); Cp,m(liquid water) = 75.29 J K-1 mol-1; Cp,m(water vapor) = 35.96 J K-1 mol-1; Density of liquid water ρ = 0.997 g cm-3; molar mass of water M = 18.0152 g mol-1 (Assume all of these values to be independent of temperature.) Total marks in this exam: 20 (regular questions); bonus marks: 2 (questions 1d, 3c) _____________________________________________________________________________ --- END OF EXAM --- Chemistry 2290 Midterm Examination 1, Winter 2008 2 ...
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This note was uploaded on 06/12/2010 for the course CHEM 2290 taught by Professor Georgschreckenbach during the Winter '09 term at Manitoba.

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