Entropy of Mixing (1) S.J.T.U. Phase Transformation and Applications To calculate the entropy of mixing of two ideal gases. One gas expands isothermally from V to Vr in the apparatus shown schematically below. nR VT aT ideal gas Initially fds-fav nf ndiny Va evacuated S2-S,nRIn H U SJTU Thermodynamics of Materials Spring2010©X.J.Jin Lecture 6 Property Relation llPhase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2010 © X. J. Jin Lecture 6 Property Relation II Entropy of Mixing (1) dV n Rd V V nR dS T a T a V V V V S S ln 2 1      To calculate the entropy of mixing of two ideal gases. ideal gas V nR T P V S T V                   Va VT Initially evacuated One gas expands isothermally from Va to VT in the apparatus shown schematically below. a T V V S2  S1  nRln