Barometric equation S.J.T.U. Phase Transformation and Applications The points 1 and 2 are at different altitudes.If the two are at equilibrium. G2-G1+Mg(22-21)=0 Figure 4.2 Equilibrium between top and bottom of a column of gas at constant temperature. At constant temperature,assuring ideal gas behavior dG-Vdp-RTdp-RTdln p) G2-G RTIn P2 p RTIn P2+Mg(2-1)=0 P Represent the variation of pressure with height for an ideal gas. SJTU Thermodynamics of Materials Spring2007©X.J.Jin Lecture 7 equilibrium IPhase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2007 © X. J. Jin Lecture 7 equilibrium I Barometric equation • The points 1 and 2 are at different altitudes. If the two are at equilibrium. 0)( − 12 + − zzMgGG 12 = At constant temperature, assuring ideal gas behavior ( ) pRTddp p RT dpVGd === ln 1 2 12 ln p p =− RTGG 12 0)(ln 1 2 zzMg =−+ p p RT ⎥⎦⎤ ⎢⎣⎡ 12 −−= zz 12 )(exp RTMg pp Represent the variation of pressure with height for an ideal gas