Answer the following questions based on the P-T phase diagram of CO2.(a) CO2 at 1 atm pressure and temperature −60oC is compressed isothermally. Does it go through a liquid phase?
(b) What happens when CO2 at 4 atm pressure is cooled from room temperature at constant pressure? (c) Describe qualitatively the changes in a given mass of solid CO2 at 10 atm pressure and temperature −65oC as it is heated up to room temperature at constant pressure .(d) CO2 is heated to a temperature 70oC and compressed isothermally. What changes in its properties do you expect to observe?
(b) What happens when CO2 at 4 atm pressure is cooled from room temperature at constant pressure?
The P-T phase diagram for CO2 is shown in the following figure:
(a) Since the temperature −60oC lies to the left of −56.6oC on the curve i.e. lies in the region vapour and solid phase, so carbon dioxide will condense directly into the solid without becoming liquid.
(b) Since the pressure 4 atm is less than 5.11 atm the carbon dioxide will condense directly into solid without becoming liquid.
(c) When a solid CO2 at 10 atm pressure and −65oC temperature is heated, it is first converted into liquid. A further increase in temperature brings it into the vapour phase. At P = 10 atm, if a horizontal line is drawn parallel to the T-axis, then the points of intersection of this line with the fusion and vaporization curve will give the fusion and boiling points of CO2 at 10 atm.
(d) Since 70oC is higher than the critical temperature of CO2, so the CO2 gas can not be converted into the liquid state on being compressed isothermally at 70oC. It will remain in the vapour state. However, the gas will depart more and more from its perfect gas behavior with the increase in pressure.
The P-T phase diagram for CO2 is shown in the following figure:
(a) Since the temperature −60oC lies to the left of −56.6oC on the curve i.e. lies in the region vapour and solid phase, so carbon dioxide will condense directly into the solid without becoming liquid.
(b) Since the pressure 4 atm is less than 5.11 atm the carbon dioxide will condense directly into solid without becoming liquid.
(c) When a solid CO2 at 10 atm pressure and −65oC temperature is heated, it is first converted into liquid. A further increase in temperature brings it into the vapour phase. At P = 10 atm, if a horizontal line is drawn parallel to the T-axis, then the points of intersection of this line with the fusion and vaporization curve will give the fusion and boiling points of CO2 at 10 atm.
(d) Since 70oC is higher than the critical temperature of CO2, so the CO2 gas can not be converted into the liquid state on being compressed isothermally at 70oC. It will remain in the vapour state. However, the gas will depart more and more from its perfect gas behavior with the increase in pressure.
