Phase diagrams for carbon dioxide

FIGURE 8-7 The phase diagram for carbon dioxide (not to scale). The liquid can exist only at pressures above 5.1 atm. Note the slope of the boundary between the solid and liquid phases it shows that the freezing point rises as pressure is applied. 

Self-Test 8.4A From the phase diagram for carbon dioxide (Fig. 8.7), predict which is more dense, the solid or the liquid phase. Explain your conclusion. 

Self-Test 8.5A The phase diagram for carbon dioxide is shown in Fig. 8.7. Describe the physical states and phase changes of carbon dioxide as it is heated at 2 atm from — 155°C to 25°C. 

Figure 6.4 On the left is a phase diagram for carbon dioxide. Broken lines indicate isotherm crossing at either constant pressure or density. On the right is illustrated the change in solubility of naphthalene as a function of temperature and pressure.

The discovery of supercritical fluids occurred in 1879, when Thomas Andrews actually described the supercritical state and used the term critical point. A supercritical fluid is a material above its critical point. It is not a gas, or a liquid, although it is sometimes referred to as a dense gas. It is a separate state of matter defined as all matter by both its temperature and pressure. Designation of common states in liquids, solids and gases, assume standard pressure and temperature conditions, or STP, which is atmospheric pressure and 0°C. Supercritical fluids generally exist at conditions above atmospheric pressure and at an elevated temperature. Figure 16.1 shows the typical phase diagram for carbon dioxide, the most commonly used supercritical fluid [1]. 

Fig. 16.1. Phase diagram for carbon dioxide critical temperature 31.3°C critical pressure 72.9 atm.

Brady et al. [52] have discussed pressure-temperature phase diagrams for carbon dioxide polychlorobiphenyls and examined the rate process of desorption from soils. Supercritical carbon dioxide was used to extract polychlorobiphenyls and DDT and Toxaphene from contaminated soils. 

Each substance has its own phase diagram to display how temperature and pressure determine its properties. Figure 7-4 is the phase diagram for carbon dioxide. 

Look at the phase diagram for carbon dioxide (CO2) in Figure 10-lb. If you put carbon dioxide under a pressure of 4.5 atm at a temperature of 23°C, in what phase of matter would the carbon dioxide be What are the triple point and the critical point of carbon dioxide according to the phase diagram ... 

Self-Test 8.5A The phase diagram for carbon dioxide is shown in Fig. 

Carbon dioxide plays a central role in the CNG process both as a pure component and in mixture with other compounds. The triple point of carbon dioxide is referred to frequently in the following discussion it is the unique temperature and pressure at which solid, liquid, and vapor phases of carbon dioxide can exist at equilibrium (-56.6°C, 5.1 atm). The carbon dioxide triple point is shown in Figure 2, a phase diagram for carbon dioxide. 

The phase diagram for carbon dioxide (Fig. 16.58) differs significantly from that for water. The solid/liquid line has a positive slope, since solid carbon... 

The phase diagram for carbon dioxide is similar to that for water, but there are differences. In the phase diagram for carbon dioxide, the horizontal line at 101.3 kPa does not intersect the solid-liquid line. Thus, carbon dioxide is never a liquid at standard pressure. In fact, if you set dry ice, which is solid carbon dioxide, in a room temperature environment, you can see that it sublimes, or changes directly from a solid to a gas. 

Examine the phase diagram for carbon dioxide in Figure 13-28. Notice that at 1 atm pressure, the solid sublimes to a gas. What happens to the solid at much higher pressures (13.4)... 

Referring to the phase diagram for carbon dioxide shown in Figure 13-17b for approximate values, draw a heating curve similar to that in Figure 13-15 for carbon dioxide at 1 atmosphere pressure. Draw a second heating curve for carbon dioxide at 5 atm pressure. Estimate the transition temperamres. 

This is the phase diagram for carbon dioxide, CO2. It shows the same features as that of water, only at different temperatures and pressures. 

Phase diagram for carbon dioxide, illustrating re ons useful for food-processing applications."... 

The phase diagram for carbon dioxide is shown schematically in Fig. 12.7. The solid-liquid line slopes slightly to the right, since > I oiid- Note that liquid CO2 is not stable at pressures below 5 atm. For this reason dry ice is dry under ordinary atmospheric pressure. When carbon dioxide is confined to a cylinder under pressure at 25 °C, the diagram shows that if the pressure reaches 67 atm, liquid CO2 will form. Commercial cylinders of CO2 commonly contain liquid and gas in equilibrium the pressure in the cylinder is about 67 atm at 25 °C. 

The phase diagram for carbon dioxide (Fig. 10.52) differs from that for water. The solid/ liquid line has a positive slope, since solid carbon dioxide is more dense than liquid carbon dioxide. The triple point for carbon dioxide occurs at 5.1 atm and -56.6X, and the critical point occurs at 72.8 atm and 31X. At a pressure of 1 atm, solid carbon dioxide... 

Phase diagrams can provide important information for substances. For example, the phase diagram for carbon dioxide in Figure 12.30 shows why carbon dioxide sublimes at normal conditions. Find 1.0 atm on the carbon dioxide graph and follow the dashed line to the yellow line. The graph shows that carbon dioxide changes from a solid to a gas at 1 atm. If you extend the dashed line past the yellow line, the graph shows that carbon dioxide does not liquefy as temperature increases. 

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