Pick out the correct statement.

A. A real gas on expansion in vacuum gets heated up

B. An ideal gas on expansion in vacuum gets cooled

C. An ideal gas on expansion in vacuum gets heated up

D. A real gas on expansion in vacuum cools down whereas ideal gas remains unaffected

Answer: Option D

Solution(By Examveda Team)

Conside piston cylinder arrangement when the expansion occurring in vacuum there is no work has to be done by the system. But for an real gas on striking the piston losses some of its momentum and hence velocity of molecules decreases and therefore cooling takes place. But for an ideal gas since its velocity doesn’t changes the temperature remains same.