The molar entropy of argon is 36.0 cal/K-mol at 200 K and 2 atm. A sample is heated at constant volume to 800 K and then expanded isothermally and reversibly at 800 K until its pressure returns to 2 a

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The molar entropy of argon is 36.0 cal/K-mol at 200 K and 2 atm. A sample is heated at constant volume to 800 K and then expanded isothermally and reversibly at 800 K until its pressure returns to 2 atm. Its molar entropy at the end is (R = 2 cal/K-mol, ln 2 = 0.7)

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Constant-volume heating: Δ S 1 = C V ln(800/200) = 3 × ln 4 = 3 × 1.4 = 4.2 cal/K-mol. The pressure rises to 2 × 4 = 8 atm. Isothermal expansion from 8 atm to 2 atm: Δ S 2 = Rln(8/2) = 2 × 1.4 = 2.8 cal/K-mol. S = 36.0 + 4.2 + 2.8 = 43.0 cal/K-mol. Check: same as isobaric heating at 2 atm, 36.0 + 5ln 4 = 43.0. Matches (d).

Chemistry - Thermodynamics - II Question with Solution | TestHub

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