Question

An ideal gas obeying kinetic theory of gases can be liquefied if

• A. Its pressure is more than critical pressure $P_C$
• B. Its temperature is more than critical temperature $T_C$
• C. Its pressure is more than $P_C$ at a temperature less than $T_C$
• D. It cannot be liquefied at any value of P and T

Answer 1

The correct option is D It cannot be liquefied at any value of P and T

A gas can be liquified only if there is intermolecular attractive forces occuring among the gas particles. A gas with non-zero intermoleular force (i.e., any real gas) can be liquified by applying the pressure provided the temperature is less than its critical temperature ($T_C$). In ideal gas, there is no intermolecular attraction and hence the gas cannot be liquified at any value of P and T.