Excess molar enthalpies of {xH2O +(1 –x)C5H12}(g) up to 698.2 K and 14.0 MPa

Abstract

Excess molar enthalpies, H^E_m, of {xH₂O +(1 –x)C₅H₁₂} have been measured at temperatures from 448.2 to 698.2 K and at pressures up to 14.0 MPa. H^E_m is defined as the residual enthalpy of the mixture minus the mole-fraction-weighted mean of the pure component residual enthalpies. The residual enthalpy H^*_m of n-pentane was calculated from virial coefficients B and C, and H^*_m of water was calculated using coefficients B, C and D, which are consistent with the NBS/NRC steam tables. H^*_m for the mixture was calculated from cross-term B₁₂ values obtained by combining Stockmayer parameters, ε/k_B= 233 K, σ= 0.312 nm and t^*= 1.238 for water with Kihara parameters for n-pentane, and cross-terms C₁₁₂ and C₁₂₂ obtained from the Orbey–Vera third virial coefficient corresponding states correlation using fluoromethane parameters in place of those for water in non-associative interactions. H^E_m values calculated from the virial equation of state are in good agreement with experiment.