Solved Exam 3 Questions - Principles of Chemistry I | CH 301 | FOR QUALITY GRADES

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Version 097 – CH 301 Exam 3 2013 – laude – (52090) 1 This print-out should have 30 questions. Multiple-choice questions may continue on the next column or page – find all choices before an... swering. 001 5.0 points Which of the following is not a definition of enthalpy or change in enthalpy? 1. ∆H = Hf inal − Hinitial 2. The heat transfer at constant volume correct 3. A state function that influences the spontaneity of a reaction 4. ∆H = ∆E + P ∆V Explanation: The heat transfer at constant volume is equal to the change in internal energy, not the change in enthalpy. The other choices are all mathematical identities relating to enthalpy or change in enthalpy or prose restatements of these mathematical identities. 002 5.0 points What is the residual entropy of 0.5 moles of CH3Cl? 1. 0 J · mol−1 · K −1 2. 11.52 J · mol−1 · K −1 3. 9.13 J · mol−1 · K −1 4. 5.76 J · mol−1 · K −1 correct Explanation: S = k · ln W = k · ln  4 0.5 NA  = NA k · ln(2) = R ln(2) = 5.76 J · mol−1 · K −1 003 5.0 points The enthalpy of vaporization of acetone is 31.3 kJ/mol, and its boiling point is 56.3◦C. What is the entropy change for the vaporization (boiling) of acetone? 1. 556 J/mol K 2. 556 kJ/mol K 3. Not enough information is given. 4. 10.5 kJ/mol K 5. 95.0 J/mol K correct Explanation: 004 5.0 points Which of the reactions below will likely have the largest increase in entropy (∆Srxn)? 1. C5H12(ℓ) + 8 O2(g) → 6 H2O(g) + 5 CO2(g) correct 2. N2H4(g) + H2(g) → 2 NH3(g) 3. Na+(g) + Cl−(g) → NaCl(s) 4. S3(g) + 9 F2(g) → 3 SF6(g) 5. 2 CH4(g) + 2O3(g) → 4 H2O(g) + 2 CO(g) Explanation: The reaction with the greatest positive value for ∆ngas will have the greatest value of ∆Srxn. 005 5.0 points Calculate ∆Suniverse for the condensation of methanol (CH3OH) at 10◦C if the S ◦ m for CH3OH(g) and CH3OH(ℓ) are 240 J · mol−1 · K −1 and 127 J · mol−1 · K −1 , respectively. Assume the standard boiling point of methanol is 65◦C. 1. 135 J · mol−1 · K −1 2. −135 J · mol−1 · K −1 3. 113 J · mol−1 · K −1 [Show More]

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