Entropy ideal-gas

The variation of Cp for crystalline thiazole between 145 and 175°K reveals a marked inflection that has been attributed to a gain in molecular freedom within the crystal lattice. The heat capacity of the liquid phase varies nearly linearly with temperature to 310°K, at which temperature it rises more rapidly. This thermal behavior, which is not uncommon for nitrogen compounds, has been attributed to weak intermolecular association. The remarkable agreement of the third-law ideal-gas entropy at... 

Cmpd. no. Name Formula CAS no. Mol wt Ideal gas enthalpy of formation, J/kmol X lE-07 Ideal gas Gihhs energy of formation, J/kmol X lE-07 Ideal gas entropy, J/(kmol-K) X lE-05 Standard net enthalpy of combustion, J/kmol X lE-09... 

TABLE 2-223 Ideal Gas Entropies/ s" , kJ/kgmol K/ of Combustion Products... 

Table 4.2 Comparison of the ideal gas entropy in J K mol 1 at a pressure of 101.32 kPa as calculated from the Third Law and from the statistical equations...

Fig. 4.7 Scheme of statistical thermodynamic calculations of ideal-gas entropy for the compounds without internal rotation... 

Quantum mechanics clearly denies the possibility of distinguishing between particles in translational motion.16 For the ideal gas entropy, we must therefore use Eq. (34) for indistinguishable particles ... 

The heat capacity of thiazole was determined by adiabatic calorimetry from 5 to 340°K by Goursot and Westrum (295,296). A glass-type transition occurs between 145 and 175 K. Melting occurs at 239.53°K (-33.62°C) with an enthalpy increment of 2292 cal mole" and an entropy increment of 9.57 cal mole" -"K". Table 1-44 summarizes the variations as a function of temperature of the most important thermodynamic properties of thiazole molar heat capacity Cp, standard entropy S°, and Gibbs function -(G°-The variation of Cp for crystalline thiazole between 145 and 175°K reveals a marked inflection that has been attributed to a gain in molecular freedom within the crystal lattice. The heat capacity of the liquid phase varies nearly linearly with temperature to 310°K, at which temperature it rises more rapidly. This thermal behavior, which is not uncommon for nitrogen compounds, has been attributed to weak intermolecular association. The remarkable agreement of the third-law ideal-gas entropy at... 

Equation (16.20) for the molar entropy of an ideal gas allows calculation of absolute entropies for tile ideal-gas state. The data required for evaluation of the last two terms on tlie right are tlie bond distances and bond angles in the molecules, and the vibration frequencies associated witli tlie various bonds, as determined from spectroscopic data. The procedure lias been very successful in the evaluation of ideal-gas entropies for molecules whose atomic stractures are known. 

Valentine (1.)] used low-temperature calorimetric data to derive the ideal gas entropy at the normal boiling point of 190.97 K. The experimental value of 57.18 cal K mol is in good agreement with 57.216 cal K mol obtained from this table. Schwing ( ) measured C for CHFg vapor (25-100 C) and confirmed that the vibrational assignment is adequate. 

Furukawa (1 ) reported low-temperature calorimetric data from which the ideal gas entropy may be derived as 64.54 0.09 ca... 

Example Estimate the standard and ideal gas entropies of formation of o-toluidine. 

These have been obtained as photoemission work function w (cf. Fig. 1) at the electron electrode equilibrium potential (which for hexamethylphosphotriamide and liquid ammonia was measured by experiment, and, for water, calculated from the thermochemical data ) by making a correction for the ideal gas entropy according to Eq. (3) ri . It should be noted that the aforementioned value, computed in this manner, is independent of the solvated electron concentration (for the same standard concentration of localized and delocalized electrons). 

Ideal gas entropy change with T and Y as independent variables if Cy is a constant... 

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