The gaseous speed of sound, the ideal gas heat capacity at constant pressure, and the second Virial coefficient were determined for pentafluoroethane (HFC 125). A total of 49 data points of speed of sound for gas...The gaseous speed of sound, the ideal gas heat capacity at constant pressure, and the second Virial coefficient were determined for pentafluoroethane (HFC 125). A total of 49 data points of speed of sound for gaseous HFC 125 were measured for temperatures from 273 to 313 K and pressures from 32 to 479 kPa with a cylindrical, variable path acoustic interferometer. The ideal gas heat capacity at constant pressure and the second acoustic Virial coefficient were determined over the temperature range from the speed of sound measurements and were correlated as functions of temperature. An analytical expression for the second Virial coefficient derived using the square well intermolecular potential model was compared with the data.展开更多
The thermodynamic properties of xanthone（XTH） and 135 polybrominated xanthones（PBXTHs） in the standard state have been calculated at the B3LYP/6-31G＊ level using Gaussian 03 program.The isodesmic reactions were d...The thermodynamic properties of xanthone（XTH） and 135 polybrominated xanthones（PBXTHs） in the standard state have been calculated at the B3LYP/6-31G＊ level using Gaussian 03 program.The isodesmic reactions were designed to calculate the standard enthalpy of formation（△fHθ） and standard free energy of formation（△fGθ） of PBXTH congeners.The relations of these thermodynamic parameters with the number and position of Br atom substitution（NPBS） were discussed,and it was found that there exist high correlation between thermodynamic parameters（entropy（Sθ）,△fHθ and △fGθ） and NPBS.According to the relative magnitude of their △fGθ,the relative stability order of PBXTH congeners was theoretically proposed.The relative rate constants of formation reactions of PBXTH congeners were calculated,Moreover,the values of molar heat capacity at constant pressure（Cp,m） from 200 to 1000 K for PBXTH congeners were also calculated,and the temperature dependence relation of them was obtained,suggesting very good relationships between Cp,m and temperature（T,T^1 and T^2） for almost all PBXTH congeners.展开更多
With the B3LYP calculation method of density functional theory（DFT）and the 6-31G＊ basis set,full optimization calculation was made for phenoxathiin10-oxide（PTO）and 135 polybromine phenoxathiin 10-oxides（PBPTOs）...With the B3LYP calculation method of density functional theory（DFT）and the 6-31G＊ basis set,full optimization calculation was made for phenoxathiin10-oxide（PTO）and 135 polybromine phenoxathiin 10-oxides（PBPTOs）with the Gaussian 03 program and molar heat capacity in constant volume（CVθ）value of each molecule in the standard state was obtained.The relation between CVθ and the substitution position and number of bromine atom（NPBS）was studied,and the results indicated good correlation（R2 = 1.000）between CVθ and NPBS of PBPTO compounds.Based on the output file of Gaussian 03 program,molar heat capacity at constant pressure（Cp,m）of PBPTO compounds from 200 to 1,000 K was calculated with the statistical thermodynamics program,and the correlation equation between Cp,m and temperature（T,T-1 and T-2）was obtained with the least-squares method,and the correlation coefficient of the correlation equation（R2）was 1.000.In addition,based on the partition function of each molecule calculated by vibration analysis,the relative rate constant of formation of each molecule was calculated.展开更多
An equation for the specific heat capacity of liquids which contains four constants hasbeen developed in this paper by means of analysis of data of heat capacities and properties offunction curves and its form is simp...An equation for the specific heat capacity of liquids which contains four constants hasbeen developed in this paper by means of analysis of data of heat capacities and properties offunction curves and its form is simple and convenient for use. It is testified that the equationhas good extrapolating property and so cp values of subcooled liquids which are deficient canbe predicted by that of saturated liquids and vice versa.展开更多
The speed of sound of the gaseous difluoromethane (HFC-32) and trifluoroiodomethane(CF3I) are measured with a cylindrical, variable-path acoustic interferometer operating at156.252 kHz. Temperatures ranged from 273.15...The speed of sound of the gaseous difluoromethane (HFC-32) and trifluoroiodomethane(CF3I) are measured with a cylindrical, variable-path acoustic interferometer operating at156.252 kHz. Temperatures ranged from 273.15 K to 333.15 K for both and pressures rangedfrom 48 kPa to 390 kPa for HFC-32 and from 58 to 276 kPa for CF3I, respectively Theuncertainty of the speed of sound was less than ±0.1%. The ideal-gas heat capacity atconstant pressure and the second acoustic virial coefficients for HFC-32 and CF3I werealso determined over the temperature range from the speed of sound measurements. Theideal-gas heat capacities at constant pressure and second virial coefficients calculated fromthese speed of sound measurements for both were compared with results from the literaturedetermined from PVT measurements and from speed of sound measurements, respectively.The uncertainty of the ideal-gas heat capacities at constant pressure were estimated to beless than ±1%.展开更多
基金Supported by the National Natural Science Foundation of China( No. 5 990 60 0 6)
文摘The gaseous speed of sound, the ideal gas heat capacity at constant pressure, and the second Virial coefficient were determined for pentafluoroethane (HFC 125). A total of 49 data points of speed of sound for gaseous HFC 125 were measured for temperatures from 273 to 313 K and pressures from 32 to 479 kPa with a cylindrical, variable path acoustic interferometer. The ideal gas heat capacity at constant pressure and the second acoustic Virial coefficient were determined over the temperature range from the speed of sound measurements and were correlated as functions of temperature. An analytical expression for the second Virial coefficient derived using the square well intermolecular potential model was compared with the data.
基金Supported by the NNSFC (20737001, 20977046)NSF of Zhejiang Province (2008Y507280)
文摘The thermodynamic properties of xanthone（XTH） and 135 polybrominated xanthones（PBXTHs） in the standard state have been calculated at the B3LYP/6-31G＊ level using Gaussian 03 program.The isodesmic reactions were designed to calculate the standard enthalpy of formation（△fHθ） and standard free energy of formation（△fGθ） of PBXTH congeners.The relations of these thermodynamic parameters with the number and position of Br atom substitution（NPBS） were discussed,and it was found that there exist high correlation between thermodynamic parameters（entropy（Sθ）,△fHθ and △fGθ） and NPBS.According to the relative magnitude of their △fGθ,the relative stability order of PBXTH congeners was theoretically proposed.The relative rate constants of formation reactions of PBXTH congeners were calculated,Moreover,the values of molar heat capacity at constant pressure（Cp,m） from 200 to 1000 K for PBXTH congeners were also calculated,and the temperature dependence relation of them was obtained,suggesting very good relationships between Cp,m and temperature（T,T^1 and T^2） for almost all PBXTH congeners.
基金supported by the National Natural Science Foundation of China (41071319,20977046 and 20737001)
文摘With the B3LYP calculation method of density functional theory（DFT）and the 6-31G＊ basis set,full optimization calculation was made for phenoxathiin10-oxide（PTO）and 135 polybromine phenoxathiin 10-oxides（PBPTOs）with the Gaussian 03 program and molar heat capacity in constant volume（CVθ）value of each molecule in the standard state was obtained.The relation between CVθ and the substitution position and number of bromine atom（NPBS）was studied,and the results indicated good correlation（R2 = 1.000）between CVθ and NPBS of PBPTO compounds.Based on the output file of Gaussian 03 program,molar heat capacity at constant pressure（Cp,m）of PBPTO compounds from 200 to 1,000 K was calculated with the statistical thermodynamics program,and the correlation equation between Cp,m and temperature（T,T-1 and T-2）was obtained with the least-squares method,and the correlation coefficient of the correlation equation（R2）was 1.000.In addition,based on the partition function of each molecule calculated by vibration analysis,the relative rate constant of formation of each molecule was calculated.
文摘An equation for the specific heat capacity of liquids which contains four constants hasbeen developed in this paper by means of analysis of data of heat capacities and properties offunction curves and its form is simple and convenient for use. It is testified that the equationhas good extrapolating property and so cp values of subcooled liquids which are deficient canbe predicted by that of saturated liquids and vice versa.
文摘The speed of sound of the gaseous difluoromethane (HFC-32) and trifluoroiodomethane(CF3I) are measured with a cylindrical, variable-path acoustic interferometer operating at156.252 kHz. Temperatures ranged from 273.15 K to 333.15 K for both and pressures rangedfrom 48 kPa to 390 kPa for HFC-32 and from 58 to 276 kPa for CF3I, respectively Theuncertainty of the speed of sound was less than ±0.1%. The ideal-gas heat capacity atconstant pressure and the second acoustic virial coefficients for HFC-32 and CF3I werealso determined over the temperature range from the speed of sound measurements. Theideal-gas heat capacities at constant pressure and second virial coefficients calculated fromthese speed of sound measurements for both were compared with results from the literaturedetermined from PVT measurements and from speed of sound measurements, respectively.The uncertainty of the ideal-gas heat capacities at constant pressure were estimated to beless than ±1%.
