Which of the following is incorrect for critical temperature ?

Options

A. It is the highest temperature at which liquid and vapour can coexist
B. Beyond the critical temperature, there is no distinction between the two phases and a gas cannot be liquefied by compression
C. At critical temperature the surface tension of the system is zero
D. At critical temperature the gas and the liquid phases have different critical densities

Answer

D

Explanation

(a) A gas cannot be liquefied beyond the critical temperature so it is the highest temperature at which liquid and vapour can co-exist. (b) Beyond the critical temperature a gas cannot be liquefied by compression because the kinetic energy of molecules is very high. (c) At critical temperature, the intermolecular forces for liquid and gases become equal and liquid can expand without any restriction. So surface tension vanishes at critical temperature.