Crystalline thermodynamic properties

Anhydrous Hydrogen Chloride. Anhydrous hydrogen chloride is a colorless gas that condenses to a colorless liquid and freezes to a white crystalline solid. The physical and thermodynamic properties of HCl are summarized in Table 2 for selected temperatures and pressures. Figure 1 shows the temperature dependence of some of these properties. 

Physical Properties. Pure, anhydrous lactic acid is a white, crystalline soHd with a low melting poiat. However, it is difficult to prepare the pure anhydrous form of lactic acid generally, it is available as a dilute or concentrated aqueous solution. The properties of lactic acid and its derivatives have been reviewed (6). A few important physical and thermodynamic properties from this reference are summarized ia Table 1. 

Thermodynamic Properties. The thermodynamic melting point for pure crystalline isotactic polypropylene obtained by the extrapolation of melting data for isothermally crystallized polymer is 185°C (35). Under normal thermal analysis conditions, commercial homopolymers have melting points in the range of 160—165°C. The heat of fusion of isotactic polypropylene has been reported as 88 J/g (21 cal/g) (36). The value of 165 18 J/g has been reported for a 100% crystalline sample (37). Heats of crystallization have been determined to be in the range of 87—92 J/g (38). 

The mineralogical, structural, physical, and thermodynamic properties of the various crystalline alumiaa hydrates are Hsted ia Tables 1, 2, and 3, respectively. X-ray diffraction methods are commonly used to differentiate between materials. Density, refractive iadex, tga, and dta measurements may also be used. 

Table 5. Thermodynamic Properties of Crystalline Boric Acid, B(OH)3 ...

A simple example of how molecular electronic structure can influence condensed phase liquid crystalline properties exists for molecules containing strongly dipolar units. These tend to exhibit dipolar associations in condensed phases which influence many thermodynamic properties [29]. Local structural correlations are usually measured using the Kirkwood factor g defined as... 

A number of other thermodynamic properties of adamantane and diamantane in different phases are reported by Kabo et al. [5]. They include (1) standard molar thermodynamic functions for adamantane in the ideal gas state as calculated by statistical thermodynamics methods and (2) temperature dependence of the heat capacities of adamantane in the condensed state between 340 and 600 K as measured by a scanning calorimeter and reported here in Fig. 8. According to this figure, liquid adamantane converts to a solid plastic with simple cubic crystal structure upon freezing. After further cooling it moves into another solid state, an fee crystalline phase. 

The question may then be raised as to whether insoluble monolayers may really be treated in terms of equilibrium thermodynamics. In general, this problem has been approached by considering (i) the equilibrium spreading pressure of the monolayer in the presence of the bulk crystalline surfactant, and (ii) the stability of the monolayer film as spread from solution. These quantities are obtained experimentally and are necessary in any consideration of film thermodynamic properties. In both cases, time is clearly a practical variable. 

Methylammonium chloride exits in several crystalline forms, as is evident from Figure 11.3. The thermodynamic properties of the (3 and 7 forms have been investigated by Aston and Ziemer [10] down to temperatures near 0 K. Some of their data are listed below. From the information given, calculate the enthalpy of transition from the (3 to the 7 form at 220.4 K. 

An infinitesimal transfer of glycine from the sohd phase to the solution at constant temperature, pressure, and composition of solution results in a corresponding change dJ in the thermodynamic property J of the system composed of crystalline glycine and a 1-molal aqueous solution of glycine. The application of Equation (9.32) leads to the expression... 

We have already seen that o can be related to U by means of the Debye principle. The usefulness of a will be evident later, when we treat the thermodynamic properties of crystalline substances at high T... 

The physical properties of the thallium halides have been tabulated.1 Crystalline T1F has a distorted rock-salt lattice, with two independent thallium sites.333-335 The thermodynamic properties of the solid have been reassessed.336 At high temperature, the vapor phase contains TLF and T12F2 molecules,337 and matrix isolation studies have demonstrated the presence of both T1F and T12F2 in the solid the dimers have linear symmetry.338... 

As there exists a phase equilibrium both phases must have reached in the internal thermodynamic equilibrium with respect to the arrangement and distribution of the molecules the measuring time. Therefore, no time effects or path dependencies of the thermodynamic properties in the liquid crystalline phase should be expected. To check this point for the l.c. polymer, a cut through the measured V(P) curves at 2000 bar has been made (Fig. 6) and the volume values are inserted at different temperatures in Fig. 7, which represents the measured isobaric volume-temperature curve at 2000 bar 38). It can be seen from Fig. 7 that all specific volumes obtained by the cut through the isotherms in Fig. 6 he on the directly measured isobar. No path dependence can be detected in the l.c. phase. From these observations we can conclude that the volume as well as other properties of the polymers depend only on temperature and pressure. The liquid crystalline phase of the polymer is a homogeneous phase, which is in its internal thermodynamic equilibrium within the normal measuring time. 

O Hare, P.A.G., Lewis, B.M., Susman, S. and Volin, K.J. (1990) Standard molar enthalpies of formation and transition at the temperature 298.15 K and other thermodynamic properties of the crystalline and vitreous forms of arsenic sesquiselenide (As2S3). Dissociation enthalpies of As-Se bonds. Journal of Chemical Thermodynamics, 22, 1191-206. 

As it was previously noted, Cp data are available only for C60H36 in the temperature range of 5-340 K. The heat capacity of other crystalline C60H2n have not been measured probably due to absence of the required amount of pure samples. However, thermodynamic properties of the hydrofullerenes can be calculated as accurately as it is required for calculation of equilibrium composition of their reactions. 

Table 4.6 Thermodynamic properties of C6(JH36 in the crystalline state. C°m, Aand AtqH0JT are in J-K 1-mol 1 AfH°m is in kJ-mol"1)...

The thermodynamic properties of crystalline C6QH36 calculated from the Cp =f(T) dependence are presented in Table 4.6. The experimental and calculated values at T = 298.15 K are compared in Table 4.7. 

Table 4.7 Experimental (Lebedev et al. 2000) and calculated thermodynamic properties of in the crystalline state at T-298.15 K, J-K 1mol 1...

Table 4.8 Thermodynamic properties of CmII2n in the crystalline state.C°m, Aand ll JTare...

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