Question -
Answer -
(a) No, the CO2 doesnot go through the liquid phase. The point (1.00 atm, – 60°C) is to the lift ofthe triple-point O and below the sublimation curve OA. Therefore, when CO2 iscompressed at this point at constant temperature, the point moves perpendicularto the temperature-axis and enters the solid phase region. Hence, the CO2 vapourcondenses to solid directly without going through the liquid phase.
(b) CO2 at 4.0 atm pressure and room temperature (say, 27 °C)is in vapour phase. This point (4.0 atm, 27°C) lies below the vaporation curveOC and to the right of the triple point O. Therefore, when CO2 iscooled at this point at constant pressure, the point moves perpendicular to thepressure-axis and enters the solid phase region. Hence, the CO2 vapourcondenses directly to solid phase without going through the liquid phase.
(c) When the solid CO2 at – 65 °C is heated at 10 atm pressure,it is first converted into liquid. A further increase in its temperature bringsit into the vapour phase. If a horizontal line at P = 10 atm is drawn parallelto the T-axis, then the points of intersection of line with the fusion andvaporization curve give the fusion and boiling points at 10 atm.
(d) Above 31.1°C, the gas cannot be liquefied. Therefore, on being compressedisothermally at 70°C, there will be no transition to the liquid region.However, the gas will depart, more and more from its perfect gas behaviour withthe increase in pressure.