Fall 2008 CH301 Practice Quiz 6 1. Statistical thermodynamics theory When calculating positional entropy using the Boltzmann formula (S = k·lnW), which of the following statements is/are true? I. W is a theoretical value and its actual value must be experimentally determined. II. The actual value of W is always an integer. III. The equation exactly as written above could describe one atom's or molecule's entropy. 1. I only 2. II only 3. III only 4. I and II only 5. I and III only 6. II and III only 7. I, II and III 8. None 2. Statistical thermodynamics internal energy calculation (E=0.5kT) Which of the following atoms or molecules is incorrectly paired with its total rotational energy? 1. He, 0 2. CH4, 1.5kT 3. I3-, 1.5kT 4. N2, 1kT 5. O3, 1.5kT 3. Statistical thermodynamics positional entropy calculation (S = klnW) Which of the following systems is incorrectly paired with its positional entropy at absolute zero? 1. 5 molecules of BFH2, 7.58x10-23 J·K-1 2. 100 molecules of O2, 0 J·K-1 3. 2 molecules of CFH3, 3.87x10-23 J·K-1 4. 20 molecules of HF, 1.91x10-22 J·K-1 5. 10 molecules of NH3, 1.52x10-22 J·K-1 4. Internal energy theory Which of the following statements concerning internal energy is/are true? I. Change in internal energy is never zero. II. Change in internal energy is equal to heat when volume is held constant III. Change in internal energy is equal to heat when pressure is held constant 1. I only 2. II only 3. III only 4. I and II only 5. I and II only 6. II and III only 7. I, II and III 8. None 5. Internal energy calculation (ΔU = q + w) If an expanding balloon absorbs 100 kJ of heat and exerts 300 J of work, what is its change in internal energy? 1. -99700 J 2. -200 J3. 400 J 4. 100300 J 5. 99700 J 6. Ranking system entropies Rank the following systems in terms of increasing entropy: I. 1 mole of solid carbon dioxide at 300 K II. 1 mole of solid carbon dioxide at 100 K III. 1 mole of gaseous carbon dioxide at 30 K IV. 1 mole of gaseous carbon dioxide and 1 mole of gaseous oxygen at 500 K V. 1 mole of gaseous carbon dioxide at 500 K 1. III < II < I < V< IV 2. III < I < III < IV < V 3. V < IV < III < II < I 4. II < III < IV < V < I 5. I < III < II < V < IV 7. Calculation of ΔS from heat transfer If a given system absorbs 1000 J of heat, what will ΔSsurroundings be if this takes place at 127 °C? 1. 3.5 J·K-1 2. 3.0 J·K-1 3. 2.5 J·K-1 4. 4.5 J·K-1 5. 5.2 J·K-1 8. Calculation involving the second law equation Consider the evaporation of water at standard pressure at 101 °C. Even without knowing the exact values in ΔSvap and ΔHvap, what can you say about the value of ΔSsystem for this process. 1. ΔSsystem would be a small positive number. 2. ΔSsystem would be a small negative number. 3. ΔSsystem would be a large negative number. 4. ΔSsystem would be a large positive
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