Chemistry - Thermodynamics - I Question with Solution | TestHub
Assume ideal gas behaviour for all the gases considered and vibrational degrees of freedom to be active. Separate equimolar samples of Ar, N2, H2O and NH3 are initially at the same temperature and pressure and are subjected to a two-step process.
Step I: All undergo reversible adiabatic compression to half the original volume, causing a rise in their temperature.
Step II: After Step I, heat is removed isochorically from each to restore the original temperature.
Which of the following is/are correct statement(s)?
Options:(select one or more)
Answer:
Solution:
Cv,m with all vibrations active: Ar 1.5R, N2 3.5R, H2O (nonlinear, 3 vibrations) 6R, NH3 (nonlinear, 6 vibrations) 9R. Step I: T2 = T1 2R/Cv, so Δ T/T1 = 2R/Cv - 1 is largest for Ar: (b) true. Heat removed in Step II per mole in units of RT1: (Cv/R)(2R/Cv - 1) = Ar 0.881, N2 0.767, H2O 0.735, NH3 0.721. The maximum is for Ar and the minimum for NH3: (a) false, (d) true. Initial and final T are equal, so Δ U = 0: (c) true. Ans: (b), (c), (d).
