Phase Diagrams



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Phase-Diagrams

The normal melting and boiling points of water are found in exactly the same way as we have already discussed - by determining where the 1 atm pressure line crosses the solid-liquid, and then the liquid-vapor equilibrium lines. The normal melting point of water is 273 K (0 oC), and its normal boiling point is 373 K (100 oC).

How does the phase diagram for carbon dioxide look like?

How does the phase diagram for carbon dioxide look like?

How does the phase diagram for carbon dioxide look like?

How does the phase diagram for carbon dioxide look like?

The Phase Diagram for Carbon Dioxide

The only thing special about this phase diagram is the position of the triple point, which is well above atmospheric pressure. It is impossible to get any liquid carbon dioxide at pressures less than 5.2 atmospheres.

At 1 atm pressure, carbon dioxide will sublime at a temperature of 197.5 K (-75.5 °C). This is the reason why solid carbon dioxide is often known as "dry ice." There is no liquid carbon dioxide under normal conditions - only the solid or the vapor.

Based from the phase diagrams of water and carbon dioxide, answer the following questions and justify your answers:

Based from the phase diagrams of water and carbon dioxide, answer the following questions and justify your answers:

1. You have ice at 263 K (-10.0 oC) and 1.0 atm. What could you do to make the ice sublime?

2. A sample of dry ice (solid CO2) is cooled to 173 K (-100.0 oC), and is set on a table at room temperature (298 K; 25 oC). At what temperature is the rate of sublimation and deposition the same (assume that pressure is held constant at 1 atm)?


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