Vapor pressure data for water

Construct a Cox chart for n-hexane using the vapor pressure data given in Table 6. Use vapor pressure data for water to construct the arbitrary temperature scale. 

Fractionation within the hydrosphere occurs almost exclusively during vapor-to-liquid or vapor-to-solid phase changes. For example, it is evident from the vapor pressure data for water (21.0, 20.82, and 19.51 mm Hg for H2 0, H2 0, and HD O, respectively) that the vapor phase is preferentially enriched in the lighter molecular species, the extent depending on the temperature (Raleigh distillation). The progressive formation and removal of raindrops from a cloud and the formation of crystals from a solution too cool to allow diffusive equilibrium between the crystal interior and the liquid, that is, isotopic reactions carried out in such a way that the products are isolated immediately after formation from the reactants, show a characteristic trend in isotopic composition. 

As explained in Appendix M, you can estimate the values of the coefficients in Eq. (3.32) by the method of least squares. We look at another way, a graphical method. Over very wide temperature intervals experimental data will not prove to be exactly linear as indicated by Eq. (3.31), but have a slight tendency to curve. This curvature can be straightened out by using a special plot known as a Cox chart. The In or logic of the vapor pressure of a compound is plotted against a special nonlinear temperature scale constructed from the vapor-pressure data for water (called a reference substance). 

Vapor pressure data for water are given in Problem 8.D10. This data can be fit to an Antoine equation form with C = 273.16. The vapor pressure of 1-octanol is predicted by the Antoine equation ... 

Figure4.4 shows the possibly simplest of all phase diagrams in the t-v- and in the 1-p-plane. The solid line in the upper diagram is the same as the dashed line, i.e. the phase coexistence curve, in Fig. 4.1. The dotted line is the spinodal. The lower graph shows the phase boundary between gas and liquid in the pressure-temperature plane. Notice that here no coexistence region appears because the pressure is constant throughout this region (at constant t). The crosses are vapor pressure data for water taken from HCP.

The octahydrate is prepared by dissolving BaO in hot water for several hours, filtering off undissolved impurities, then cooling the solution to effect crystallization. Vapor pressure data for the octahydrate (20) is... 

B. Example Calculation The Antoine Equation for Water. Table V. l lisls the vapor pressure dalu for water from 20 to 80°C. Values of au, ba, and c0 are calculated from the data at 20, 50, and 80°C by solving the following three simultaneous equations ... 

VL(L) E measurements for binaries involving water with alcohol and acid have been done, as described elsewhere [2]. Figure 8.6 presents experimental vapor pressure data for 2-ethylhexyl laurate. The normal boiling point (nbp) is 607.6 K, close to the prediction by Gani s method. On the other hand, the prediction of the whole saturation curve by Riedel s method (noted estimation in Figure 8.6) is in large error at lower pressures. This fact can affect the accuracy of chemical equilibrium calculation, but fortunately the errors compensate each other [2]. 

Given in the literature are vapor pressure data for acetaldehyde and its aqueous solutions (1—3) vapor—liquid equilibria data for acetaldehyde—ethylene oxide [75-21-8] (1), acetaldehyde—methanol [67-56-1] (4), sulfur dioxide [7446-09-5]— acetaldehyde—water (5), acetaldehyde—water—methanol (6) the azeotropes of acetaldehyde—butane [106-97-8] and acetaldehyde—ethyl ether (7) solubility data for acetaldehyde—water—methane [74-82-8] (8), acetaldehyde—methane (9) densities and refractive indexes of acetaldehyde for temperatures 0—20°C (2) compressibility and viscosity at high pressure (10) thermodynamic data (11—13) pressure—enthalpy diagram for acetaldehyde (14) specific gravities of acetaldehyde—paraldehyde and acetaldehyde—acetaldol mixtures at 20/20°C vs composition (7) boiling point vs composition of acetaldehyde—water at 101.3 kPa (1 atm) and integral heat of solution of acetaldehyde in water at 11°C (7). 

Parks, G.S., Barton, B. (1928) Vapor pressure data for isopropyl alcohol and tertiary butyl alcohol. J. Am. Chem. Soc. 50, 24—50. Pasanen, M., Uusi-Kyyny, R, Pokki, J.-R, Pakkanen, M., Aittamaa, J. (2004) Vapor-hquid equilibrium for 1-propanol -1- 1-butene, -1- cis-2-butene, -1- 2-methyl-1-propene, -1- fra i-2-butene, -1- -butane, and -1- 2-methyl-propane. J. Chem. Eng. Data 49, 1628-1634. Petriris, V.E., Geankopolis, C.J. (1959) Phase equilibrium in 1-butanol-water-lactic acid system. J. Chem. Eng. Data 4, 197-198. Pitter, P. (1976) Determination of biological degradability of organic substances. Water Res. 10, 231. 

The above approximate guideline for an ideally dilute solution can only be made more exact by examining vapor pressure data for a specific system. The case of the methanol-water system discussed earlier is used as an illustration. For very dilute solutions, that is, when VMeOH is less than 0.04, the vapor pressure of methanol is linear in its mole fraction. This is the region where Henry s law is obeyed. As the mole fraction increases, the actual vapor pressure falls below that predicted by Henry s law, quite significant deviations being found when Xmeoh reaches 0.1. Henry s law for component B in a two-component system of A and B may be expressed as... 

A liquid containing 25 mole percent toluene, 40 mole percent ethylbenzene, and 35 mole percent water is subjected to a continuous flash distillation at a total pressure of 0.5 atm. Vapor-pressure data for these substances are given in Table 18.5. Assuming that mixtures of ethylbenzene and toluene obey Raoult s law and that the hydrocarbons are completely immiscible in water, calculate the temperature and... 

Rarey, J. Horstmann, S. Gmehling, J. Vapor-liquid eqmlibria and vapor pressure data for the systems ethyl tert-butyl ether + ethanol and ethyl tert-butyl ether + water J. Chem. Eng. Data 1999,44, 532-538... 

Vapor Pressure Data for System Ethanol-Water (Ref. 12)... 

Equations (3.72) to (3.74) are solved simultaneously by trial with the vapor-pressure curve for water, which relates and and the latent-heat data. It is easiest to > .. t- which is checked when q, from Eqs. (3.72) and (3.73) agree. 

Vapor-pressure data for the hydrogen chloride-water systems are presented in Table 6-19. As can be seen, the vapor pressure of hydrogen chloride over dilute aqueous solutions is extremely low although it increases appreciably with increased temperature. The heat of solution is considerable about 240 Btu/lb of 35% hydrochloric acid produced at room temperature. Therefore, heat removal is necessary if it is desired to effect very complete removal of hydrogen chloride from a concentrated gas stream or to produce a solution of maximum concentration. This may be accomplished by using cooled absorbers or by recycling the acid through a cooler and back to the absorption unit. 

Single-Effect Evaporators The heat requirements of a singleeffect continuous evaporator can be calculated by the usual methods of stoichiometry. If enthalpy data or specific heat and heat-of-solution data are not available, the heat requirement can be estimated as the sum of the heat needed to raise the feed from feed to product temperature and the heat required to evaporate the water. The latent heat of water is taken at the vapor-head pressure instead of at the product temperature in order to compensate partiaUv for any heat of solution. If sufficient vapor-pressure data are available for the solution, methods are available to calculate the true latent heat from the slope of the Diihriugliue [Othmer, Ind. Eng. Chem., 32, 841 (1940)]. 

The vapor pressure of water, which is 24 mm Hg at 25°C, becomes 92 mm Hg at 50°C and 1 atm (760 mm Hg) at 100°C. The data for water are plotted at the top of Figure 9.2. As you can see, the graph of vapor pressure versus temperature is not a straight line, as it would be if pressure were plotted versus temperature for an ideal gas. Instead, the slope increases steadily as temperature rises, reflecting the fact that more molecules vaporize at higher temperatures. At 100°C, the concentration of H20 molecules in the vapor in equilibrium with liquid is 25 times as great as at 25°C. 

Determine the vapor pressure of heavy water, D20, and of normal water at 25°G by using data in Appendix 2A. How do these values compare with each other Using your knowledge of intermolecular forces, explain the reason for the difference observed. 

Rard (1992) reported the results of isopiestic vapor-pressure measurements for the aqueous solution of high-purity NiCl2 solution form 1.4382 to 5.7199 mol/kg at 298.1510.005 K. Based on these measurements he calculated the osmotic coefficient of aqueous NiCb solutions. He also evaluated other data from the literature and finally presented a set of smoothed osmotic coefficient and activity of water data (see Table IV in original reference). 

Thus, if the saturated vapor pressure is known at the azeotropic composition, the activity coefficient can be calculated. If the composition of the azeotrope is known, then the compositions and activity of the coefficients at the azeotrope can be substituted into the Wilson equation to determine the interaction parameters. For the 2-propanol-water system, the azeotropic composition of 2-propanol can be assumed to be at a mole fraction of 0.69 and temperature of 353.4 K at 1 atm. By combining Equation 4.93 with the Wilson equation for a binary system, set up two simultaneous equations and solve Au and A21. Vapor pressure data can be taken from Table 4.11 and the universal gas constant can be taken to be 8.3145 kJ-kmol 1-K 1. Then, using the values of molar volume in Table 4.12, calculate the interaction parameters for the Wilson equation and compare with the values in Table 4.12. 

The Level I calculation proceeds by deducing the fugacity capacities or Z values for each medium (see Table 1.5.3), following the procedures described by Mackay (2001). These working equations show the necessity of having data on molecular mass, water solubility, vapor pressure, and octanol-water partition coefficient. The fugacity f (Pa) common to all media is deduced as... 

A wide variety of solubilities (in units of g/m3 or the equivalent mg/L) have been reported. Experimental data have the method of determination indicated. In other compilations of data the reported value has merely been quoted from another secondary source. In some cases the value has been calculated. The abbreviations are generally self-explanatory and usually include two entries, the method of equilibration followed by the method of determination. From these values a single value is selected for inclusion in the summary data table. Vapor pressures and octanol-water partition coefficients are selected similarly. 

The pressure-temperature-composition diagram presented by Morey is shown in Fig. 8. The vapor pressure of pure water (on the P-T projection) terminates at the critical point (647 K, 220 bar). The continuous curve represents saturated solutions of NaCl in water, i.e., there is a three-phase equilibrium of gas-solution-solid NaCl. The gas-phase pressure maximizes over 400 bar at around 950 K. Olander and Liander s data for a 25 wt. % NaCl solution are shown, and T-X and P X projections given. At the pressure maximum, the solution phase contains almost 80% NaCl. 

Most of the studies of levitated droplets have involved low-vapor-pressure materials, but Tallin and his coworkers reported data for water droplets evaporating in dry nitrogen. The rapid evaporation of a water droplet requires that the experiment be automated, and this was accomplished by injecting the droplet by means of a 3,000 V dc electrical pulse applied to a flat-tipped hypodermic needle. The pulse triggered the data collection system so that phase functions and the resonance spectrum were obtained during the less than three-second duration of an experiment. From the phase function... 

We need many of their properties for safety and environmental protection, such as vapor pressure, solubility in water, and partition between oil and water. We have the data for all the PCBs with 0, 1, 2 or 10 chlorine atoms, but we have only some of the data for PCBs with three to nine chlorine atoms. 

HF (liq.). Guntz1 5 measured the heat of solution of liquid HF in water. He gave S = 4.6, whence, for HF (liq.), Qf=71.0. Kolosovskii,1 from vapor pressure data, computed V= —6.3, correcting an earlier calculation by Simons.1 In a recent investigation, Fredenhagen1 found V= -6.05 at 15°. 

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