Answer the following questions based on the P - T phase diagram of `CO_(2)` :
(a) `CO_(2)` at 1 atm pressure and temperature `-60^(@)C` is compressed isothermally. Does it go through a liquid phase ?
(b) What happens when `CO_(2)` at 4 atm pressure is cooled from room temperature at constant pressure ?
(c) Describe qualitatively the changes in a given mass of solid `CO_(2)` at 10 atm pressure and temperature `-65^(@)C` as it is heated up to room temperature at constant pressure.
(d) `CO_(2)` is heated to a temperature `70^(@)C` and compressed isothermally. What changes in its properties do you expect to observe ?

Explanation

(a) No, `CO_(2)` is in steam from at 1 atm pressure and `-60^(@)C` temperature.
It its isothermal compression is done i.e. increasing pressure with constant temperature then it directly converts into solid form without coming through liquid. (Sublimation)
(b) `CO_(2)` is in gaseous state at 4 atm pressure and `27^(@)C` temperature.
If it is clled at constant pressure then it directly converts into gaseous state without coming through liquid. It intersects at curve III.
(c) `CO_(2)` is in solid form at 10 atm pressure and `-60^(@)C` temp.
If it is heated at constant pressure then first it comes in liquid form and then in gaseous form because it intersects the fusion and vaporization curve.
(d) It is seen from phase diagram of `CO_(2)` that the above `70^(@)C` temperature it doesn.t have liquid area. Then also it reacts as an ideal gas with increase in pressure.