Vapor pressure graph

The assumption that the heat of vaporization is constant is not necessarily valid. Also, at temperatures near the critical temperature, the assumption about tire molar volume of the liquid is invalid. Thus, a vapor-pressure graph of the type given in Figure 2-6 usually results in a line with some curvature over a long temperature range. 

The deviation of vapor pressure from Raoult s law can be represented graphically by comparing the mole fractions of solvents with their vapor pressures. Graph 1 below shows only the partial pressure of the solvent as its mole fraction increases. As predicted by Raoult s law, tire relationship is linear. Graph 2 shows the vapor pressure of an ideal solution and the individual partial pressures of each solvent. Notice that the partial pressures add at every point to equal the total pressure. This must be true for any solution. Graph 3 and 4 show the deviations of nonideal solutions. The straight lines are the Raoult s law predictions and the curved lines are the actual pressures. Notice that the partial pressures still add at every point to equal the total pressure. Notice also that a positive heat of solution leads to an increase in vapor pressure, and a negative heat of solution, to a decrease in vapor pressure. 

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

Fig. 4. Fquilihrium vapor pressure of materials, where x indicates the melting point of the metal. The melting points for In and Sn ate off the graph at 156...

The chart shown in Fig. 10-25 is for pure liqmds. Extrapolation of data beyond the ranges indicated in the graph may not produce accurate results. Figure 10-25 shows the variation of vapor pressure and NPSH reductions for various hydrocarbons and hot water as a function of temperature. Certain rules apply while using this chart. When using the chart for hot water, if the NPSH reduction is greater than one-half of the NPSH reqmred for cold water, deduct one-half of cold water NPSH to obtain the corrected NPSH required. On the other hand, if the value read on the chart is less than one-half of cold water NPSH, deduct this chart value from the cold water NPSH to obtain the corrected NPSH. 

Both factors depend on the respective partial vapor pressures of water and carbon dioxide and upon the distance to the radiation source. The partial vapor pressure of carbon dioxide in the atmosphere is fairly constant (30 Pa), but the partial vapor pressure of water varies with atmospheric relative humidity. Duiser (1989) published graphs plotting absorption factors (a) against the product of partial vapor pressure and distance to flame (Px) for flame temperatures ranging from 800 to 1800 K. 

Vapor pressure data as read from tables or graphs ... 

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. 

The solubility of a solid in a liquid at its saturation vapor pressure is usually represented as a (T, x2) graph, where x2 is the mole... 

Equation (6.79) relates the slopes of the vapor pressure lines in a graph of vapor pressure against mole fraction such as those shown in Figures 6.5 to 6.8. It requires that if one of the components in a binary mixture obeys Raoult s law over the entire composition range, then the other must do the same. This can be seen as follows. If component 1 obeys Raoult s law over the entire composition range, then the slope of the graph of p against is... 

Figure 8.3 Vapor pressure (in kPa) of solid and liquid CO2 as a function of temperature. (Graphed as In p against 1 /T.) Tc is the critical temperature and Tt,p, is the triple point temperature.

The critical point is unique for (vapor + liquid) equilibrium. That is, no equivalent point has been found for (vapor + solid) or (liquid + solid) equilibria. There is no reason to suspect that any amount of pressure would eventually cause a solid and liquid (or a solid and gas) to have the same //m, Sm, and t/m. with an infinite o and at that point. mC02 was chosen for Figure 8.1 because of the very high vapor pressure at the (vapor + liquid + solid) triple point. In fact, it probably has the highest triple point pressure of any known substance. As a result, one can show on an undistorted graph both the triple point and the critical point. For most substances, the triple point is at so low a pressure that it becomes buried in the temperature axis on a graph with a pressure axis scaled to include the critical point. 

FIGURE 8.27 Raoult s law predicts that the vapor pressure of a solvent in a solution should be proportional to the mole fraction of the solvent molecules. The horizontal axis shows the mole fraction of the red molecules of substance A in the pure solute, three different solutions, and pure solvent, pictured below the graph. The vapor pressure of pure A is marked as Ppule. 

FIGURE 8.35 The vapor pressures of the two components of an ideal binary mixture obey Raoult s law. The total vapor pressure is the sum of the two partial vapor pressures (Dalton s law). The insets below the graph represent the mole fraction of A. 

Using the Clausius-Clapeyron Equation Living Graph on the Web site for this book, plot on the same set of axes the lines for AH = 15, 20., 25, and 30. kj-mol 1. Is the vapor pressure of a liquid more sensitive to changes in temperature if AH is small or large ... 

Figure 5.19.2 A graph of the vapor pressure of liquid water as a function of temperature (on the left), and a graph of the natural logarithm of the vapor pressure of water as a function of the reciprocal of temperature.

The graph of total vapor pressure vs temperature is drawn below ... 

Using a graph of the vapor pressure versus temperature, shown in Figure 6-4, the flash point of the solution is 20.5°C, or 68.9°F. 

FIGURE 12.7 A graph showing a typical example of how the vapor pressure can change with temperature. 

Tables and graphs for density, conductivity, vapor pressure activity coefficient, corrosion, and other prop.

A comparison of calculated values and experimental data for vapor pressure is shown in Figure 2-1 for a representative chemical. The graph indicates good agreement of calculations and data. 

Figure 11.5. Phase diagram for " He. Data for the melting curve and the X line from C. A. Swenson, Phys. Rev. 79, 626 (1950). Data for the evaporation curve from H. van Dijk and M. Durieux, Physica 24, 920 (1958). The evaporation curve was measured down to 0.5 K, hut the values of the vapor pressure were too small to be visible on the scale of the graph.

Cox chart chem A straight-line graph of the logarithm of vapor pressure against a special nonuniform temperature scale vapor pressure-temperature lines for many substances intersect at a common point on the Cox chart. kaks, chart cp See chemically pure. 

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