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(32-)=0 Figure 4.2 Equilibrium between top and bottom of a column of At constant temperature,assuring ideal gas behavic gas at constant temperature. dG-Vdp-RT dp-RTa(In p) G2-G)RTIn P2 p RTn2+Mg(2-)=0 pi Represent the variation of pressure with RT height for an ideal gas. SJTU Thermodynamics of Materials Fall 2018 ©X.J.Jin Lecture 7 equilibrium IPhase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Fall 2018 © X. J. Jin Lecture 7 equilibrium I Barometric equation • The points 1 and 2 are at different altitudes. If the two are at equilibrium. G2 −G1 + Mg(z2 − z1 ) = 0 At constant temperature, assuring ideal gas behavior dp RTd( p) p RT dG =Vdp = = ln 1 2 2 1 ln p p G −G = RT ln ( 2 1 ) 0 1 2 + Mg z − z = p p RT       = exp − ( − ) 2 1 2 1 z z RT Mg p p Represent the variation of pressure with height for an ideal gas