Clapeyron equation in vapor equilibria S.J.T.U. Phase Transformation and Applications Suppose the two phases in equilibrium are a △且ap vapor phase and a condensed phase Slope =- R p △Hag Assure the vapor to be an ideal gas 月→ Figure 4.5 Natural logarithms of saturation pressure versus inverse of absolute temperature. RTeg Teg d R A convenient determination of the enthalpy of evaporation of a condensed phase SJTU Thermodynamics of Materials Spring2006©X.J.Jin Lecture 7 equilibrium IPhase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2006 © X. J. Jin Lecture 7 equilibrium I Clapeyron equation in vapor equilibria Suppose the two phases in equilibrium are a vapor phase and a condensed phase vapor eq vap eq eq VT H dT dp Δ = Assure the vapor to be an ideal gas eq vap eq eq eq eq T H RT p dT dp Δ = ( ) ( ) ⎟⎠⎞ ⎜⎝ Δ ⎛ −= Δ == eq vap eqvap eq eq eq eq T d RH TH RdT p dp pd 1 ln 2 A convenient determination of the enthalpy of evaporation of a condensed phase