(a) Since -60° lies to the left of -56.6 °C On the Curve; the Vapour Will Condense directly into the Solid.
(b) Since 4 atm pressure is less than 5.11 atm . the vapour Will condense directly into Solid Without entering into the liquid region.
(c) When the Solid CO2 at -60°C is heated at 10 atm pressure, It is first converted into a liquid, A further increase in its temperature brings it into vapour Phase. If a horizontal line at p = 10 atm is drawn parallel to the T- axis, then the Points of intersection of this line With the fusion and vaporization curve give the fusoin and boiling Points at 10 atm.
(d) Above 31.1°C the gas Cannot be liquefied. Therefore, on being Compressed isothermally at 70°C, there Will be on transition to the liquid region. However the gas Will depart more and more form its perfect gas behavior With the increase in pressure.