Gases can be liquefied by:

What is meant by the vapor of a substance like $CO_2$?

What is the critical temperature $T_C$? What is its value for $CO_2$?

Which of the following gases is most difficult to liquefy?

Assertion : At critical temperature,liquid passes into gaseous state imperceptibly and continuously.
Reason : The density of liquid and gaseous phase is equal at critical temperature.

Isotherms of carbon dioxide at various temperatures are represented in the figure. Answer the following questions based on this figure.
$(i)$ In which state will $CO_2$ exist between the points $a$ and $b$ at temperature $T_1$?
$(ii)$ At what point will $CO_2$ start liquefying when temperature is $T_1$?
$(iii)$ At what point will $CO_2$ be completely liquefied when temperature is $T_2$?
$(iv)$ Will condensation take place when the temperature is $T_3$?
$(v)$ What portion of the isotherm at $T_1$ represents liquid and gaseous $CO_2$ at equilibrium?