Pressure data

A common way of following the progress of a gas phase reaction with a Change in the number of mols is to monitor the time variation of the total pressure, rc. From this information and the stoichiometry, the partial pressures of the participants can be deduced, and a rate equation developed in those terms. Usually it is adequate to assume ideal gas behavior, but nonideal behavior can be taken into account with extra effort. Problem P3.03.06 is an example of nonideality. 

In the simplest case, the rate of the reaction, A Products, becomes 

A key relation is that for the total number of mols which is determined by the stoichiometry of the reaction. This and other relations are 

Usually kc is the specific rate that is sought because the law of mass action is expressed in concentrations and Is the basis of rate equations 

Since some adulteration of raw data occurs when they are transformed mathematically, by differentiation or taking logarithms or reciprocals or otherwise, it is better from a statistical point of view to change the rate equation to read in terms of total pressure, rather than to change the data to partial pressures or concentrations. Such a transformation is worked out for a 

---

American Petroleum Institute, Bibliographies on Hydrocarbons, Vols. 1-4, "Vapor-Liquid Equilibrium Data for Hydrocarbon Systems" (1963), "Vapor Pressure Data for Hydrocarbons" (1964), "Volumetric and Thermodynamic Data for Pure Hydrocarbons and Their Mixtures" (1964), "Vapor-Liquid Equilibrium Data for Hydrocarbon-Nonhydrocarbon Gas Systems" (1964), API, Division of Refining, Washington. 

Correlation and compilation of vapor-pressure data for pure fluids. Normal and low pressure region. 

Source for liquid-liquid and vapor-liquid equilibrium data and vapor-pressure data. 

Comprehensive data collection for more than 6000 binary and multicomponent mixtures at moderate pressures. Data correlation and consistency tests are given for each data set. 

Compilation of vapor-pressure data for organic compounds data are correlated with the Antoine equation and graphs are presented. 

Vapor-liquid equilibrium data and vapor pressure data, Vol. 2 (2a) and Vol. 4 (4b) and liquid-liquid equilibrium data, Vol. 2 (2b, 2c). 

Vapor-pressure data correlated with the Antoine equation. Results displayed graphically. 

Vapor-pressure data and other thermodynamic properties. 

Presents vapor-pressure data for a large number of substances. 

P the other terms provide corrections which at low or moderate pressure are close to unity. To use Equation (2), we require vapor-pressure data and liquid-density data as a function of temperature. We also require fugacity coefficients, as discussed in Chapter 3. 

Enthalpies are referred to the ideal vapor. The enthalpy of the real vapor is found from zero-pressure heat capacities and from the virial equation of state for non-associated species or, for vapors containing highly dimerized vapors (e.g. organic acids), from the chemical theory of vapor imperfections, as discussed in Chapter 3. For pure components, liquid-phase enthalpies (relative to the ideal vapor) are found from differentiation of the zero-pressure standard-state fugacities these, in turn, are determined from vapor-pressure data, from vapor-phase corrections and liquid-phase densities. If good experimental data are used to determine the standard-state fugacity, the derivative gives enthalpies of liquids to nearly the same precision as that obtained with calorimetric data, and provides reliable heats of vaporization. 

This chapter presents quantitative methods for calculation of enthalpies of vapor-phase and liquid-phase mixtures. These methods rely primarily on pure-component data, in particular ideal-vapor heat capacities and vapor-pressure data, both as functions of temperature. Vapor-phase corrections for nonideality are usually relatively small. Liquid-phase excess enthalpies are also usually not important. As indicated in Chapter 4, for mixtures containing noncondensable components, we restrict attention to liquid solutions which are dilute with respect to all noncondensable components. 

An apparent systematic error may be due to an erroneous value of one or both of the pure-component vapor pressures as discussed by several authors (Van Ness et al., 1973 Fabries and Renon, 1975 Abbott and Van Ness, 1977). In some cases, highly inaccurate estimates of binary parameters may occur. Fabries and Renon recommend that when no pure-component vapor-pressure data are given, or if the given values appear to be of doubtful validity, then the unknown vapor pressure should be included as one of the adjustable parameters. If, after making these corrections, the residuals again display a nonrandom pattern, then it is likely that there is systematic error present in the measurements. ... 

Correlations for standard-state fugacities at 2ero pressure, for the temperature range 200° to 600°K, were generated for pure fluids using the best available vapor-pressure data. 

The correlations were generated by first choosing from the literature the best sets of vapor-pressure data for each fluid. 

At temperatures above those corresponding to the highest experimental pressures, data were generated using the Lyckman correlation all of these were assigned an uncertainty of 5% of the standard-state fugacity at zero pressure. Frequently, this uncertainty amounts to one half or more atmosphere for the lowest point, and to 1 to 5 atmospheres for the highest point. 

The subscript i refers to the initial pressure, and the subscript ab refers to the abandonment pressure the pressure at which the reservoir can no longer produce gas to the surface. If the abandonment conditions can be predicted, then an estimate of the recovery factor can be made from the plot. Gp is the cumulative gas produced, and G is the gas initially In place (GIIP). This is an example of the use of PVT properties and reservoir pressure data being used in a material balance calculation as a predictive tool. 

Bartell and co-workers report the following capillary pressure data in porous plug experiments using powdered carbon. Benzene, which wets carbon, showed a capillary pressure of 6200 g/cm. For water, the pressure was 12,000 g/cm, and for ben-... 

As stated in the introduction to the previous chapter, adsorption is described phenomenologically in terms of an empirical adsorption function n = f(P, T) where n is the amount adsorbed. As a matter of experimental convenience, one usually determines the adsorption isotherm n = fr(P), in a detailed study, this is done for several temperatures. Figure XVII-1 displays some of the extensive data of Drain and Morrison [1]. It is fairly common in physical adsorption systems for the low-pressure data to suggest that a limiting adsorption is being reached, as in Fig. XVII-la, but for continued further adsorption to occur at pressures approaching the saturation or condensation pressure (which would be close to 1 atm for N2 at 75 K), as in Fig. XVII-Ih. 

Polymer simulations can be mapped onto the Flory-Huggins lattice model. For this purpose, DPD can be considered an off-lattice version of the Flory-Huggins simulation. It uses a Flory-Huggins x (chi) parameter. The best way to obtain % is from vapor pressure data. Molecular modeling can be used to determine x, but it is less reliable. In order to run a simulation, a bead size for each bead type and a x parameter for each pair of beads must be known. 

Figure 8.9 is a plot of osmotic pressure data for a nitrocellulose sample in three different solvents analyzed according to Eq. (8.87). As required by Eq. (8.88), all show a common intercept corresponding to a molecular weight of 1.11 X 10 the various systems show different deviations from ideality, however, as evidenced by the range of slopes in Fig. 8.9. 

Figure 8.9 Osmotic pressure data plotted as n/RTc2 versus concentration for nitrocellulose in three different solvents. [Data from A. Dobry,/. Chem. Phys. 32 50 (1935).]...

Use the method described in Problem 9 to obtain values of and p from these data. How do the values of these parameters compare with the values obtained for the same system from osmotic pressure data in Problem 8 ... 

Chlorine, a member of the halogen family, is a greenish yellow gas having a pungent odor at ambient temperatures and pressures and a density 2.5 times that of air. In Hquid form it is clear amber SoHd chlorine forms pale yellow crystals. The principal properties of chlorine are presented in Table 15 additional details are available (77—79). The temperature dependence of the density of gaseous (Fig. 31) and Hquid (Fig. 32) chlorine, and vapor pressure (Fig. 33) are illustrated. Enthalpy pressure data can be found in ref. 78. The vapor pressure P can be calculated in the temperature (T) range of 172—417 K from the Martin-Shin-Kapoor equation (80) ... 

Bromine Trifluoride. Bromine trifluoride is a colorless Hquid. The commercial grade is usually amber to red because of slight bromine contamination. The molecule has a distorted T stmeture (26). Infrared spectral data (26—30), the uv-absorption spectmm (31), and vapor pressure data (32) may be found in the Hterature. 

Bromine Pentafluoride. Bromine pentafluoride is a colorless Hquid having the molecular stmeture of a tetragonal pyramid (5). The index of refraction is 1.3529 (33). Infrared spectra (13,34), the uv-absorption spectmm (35), and vapor pressure data (11) are all available. 

Chlorine Monofluoride. Chlorine monofluoride is a colorless gas that condenses to a Hquid with a slight yeUow cast and free2es to a white soHd. The infrared spectmm of gaseous chlorine monofluoride and the Raman spectmm of the Hquid have been studied (36). The uv-absorption spectmm (37) and vapor pressure data are also available (11). 

Chlorine Pentafluoride. Chlorine pentafluoride is a colorless gas at room temperature. The ir and Raman spectra of the Hquid and gas phase have been studied (34,39). The uv absorption spectmm (45) and vapor pressure data may be found in the Hterature (18). 

Iodine Pentafluoride. Iodine pentafluoride is a straw-colored Hquid the ir and Raman spectra of the gas phase have been studied (19,46,47) vapor pressure data are given in References 14 and 48. 

Ref. 87. Test method ASTM E96-35T (at vapor pressure for 25.4 p.m film thickness). Values are averages only and not for specification purposes. Original data converted to SI units using vapor pressure data from Ref. 90. 

Original data converted to SI units using vapor pressure data from Ref. 72. "At20°C. 

S. Obe, Computer Aided Data Book of Vapor Pressure, Data Book Publishing Co., Tokyo, 1976, p. 109. 

Vapor pressure data from —71 to 90°C has been given ... 

The physical properties of some common ketones are Hsted in Table 1. Ketones are commonly separated by fractional distillation, and vapor—Hquid equihbria and vapor pressure data are readily available for common ketones. A number of other temperature dependent physical properties for acetone, methyl ethyl ketone, methyl isobutyl ketone, and diethyl ketone have been pubHshed (3). 

More extensive vapor pressure data for lithium and other metals are given ia Ref. 43. To convert kPa to mm Hg, multiply by 7.5. 

---