Entropy of Mixing (2) S.J.T.U. Phase Transformation and Applications To calculate the entropy of mixing of two ideal gases. Because ideal gases do not interact,we can calculate the total entropy change as the sum of the two entropy changes of the individual gases. (S:-S)=nRIn V2+Va Va -S,=n(S2-S1)+m(S:-S1)=n.RIn +mRnV Per mole of mixture: s-S=Rn。+ ++ V。+Va na+np na+np na+np H SJTU Thermodynamics of Materials Spring2010©X.J.Jin Lecture 6 Property Relation IlPhase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2010 © X. J. Jin Lecture 6 Property Relation II Entropy of Mixing (2) To calculate the entropy of mixing of two ideal gases. Because ideal gases do not interact, we can calculate the total entropy change as the sum of the two entropy changes of the individual gases.   a a b a a V V V S S n R  2  1  ln Va VT Vb     b a b b a a b a a b b a V V V n R V V V S S n S S n S S n R    2  1  2  1  2  1  ln ln Per mole of mixture: b a b a b b a a b a b a a b V V V R n n n V V V R n n n n n S S         ln ln 2 1