Question

The internal energy of compressed real gas, as compared to that of the ideal gas at the same temperature is
A) less
B) More
C) Sometimes less, sometimes more
D) Maximum

Answer 1

Hint: Internal energy of gas is equal to sum of kinetic energy and potential energy of the molecules.
[Internal Energy $ = $ Kinetic Energy $ + $ Potential Energy]

Complete step by step answer:
The internal energy of gas is due to energy possessed due to motion of molecular motion and configuration of molecules.
In case of an ideal gas, these molecular collisions and attraction are assumed to be absent as per kinetic theory, so ideal gas that is compressed the gas molecule has not potential energy but only kinetic energy. So all the ideal gas will have equal internal energy at the same temperature.
In case of real gas or compressed gas, the molecules possess both types of internal energies unlike an ideal gas while compressing it the internal energy of the molecules is lost during collisions within the molecule and with walls of container. Hence compression at the same temperature, internal energy of compressed gas is less than internal energy of ideal gas.
[Internal energy of compressed gas < Internal energy of ideal gas]
So, when a real or compressed gas is compressed its molecules become closer, their mutual interaction becomes stronger. Negative potential energy increases. Hence, total energy of compressed gas decreases kinetic energy, same for both compressed and ideal gas.

So, the correct answer is “Option A”.

Note:
1) Concept of internal energy is used in this solution.
2) We have done a comparison between internal energy compressed gas and real gas.