Answer the following questions based on the P-T phase diagram of C\${{O}_{2}}\$:

Answer the following questions based on the P-T phase diagram of C\${{O}{2}}\$:
(i) At what temperature and pressure can the solid, liquid and vapour phases of C\${{O}
{2}}\$ co-exist in equilibrium ?
(ii) What is the effect of decrease of pressure on the fusion and boiling point of C\${{O}{2}}\$ ?
(iii) What are the critical temperature and pressure for C\${{O}
{2}}\$ ? What is their significance ?
(iv) Is C\${{O}_{2}}\$ solid, liquid or gas at
(a) - 70° C under 1 atm
(b) - 60° C under 10 atm
© 15° C under 56 atm

(i) At the triple point, i.e., temperature = - 56.6°C and pressure = 5.11 atm, the vapour/liquid and the solid phase of C\${{O}{2}}\$ exist in equilibrium.
(ii) If the pressure decreases, both fusion of C\${{O}
{2}}\$ and
boiling points decreases.
(iii) The critical temperature and pressure ofC\${{O}{2}}\$ are 31.1°C and 73.0 atm respectively. If the temperature ofC\${{O}{2}}\$ is more than 31.1°C, it cannot be liquified, howsoever large pressure we may apply to it.
(a) C\${{O}{2}}\$ will be a vapour at - 70°C at a pressure of 1 atm.
(b)C\${{O}
{2}}\$ will be solid at - 60°C at a pressure of 10
atm.
© It will be liquid at 15°C at a pressure of 56 atm