COMEDK202510 May 2025Morning ShiftPhysicsKinetic Theory of GasesActual
The mean energy per molecule for a diatomic gas is:
Options
- A( 3 2 N ) K _ B T
- B( 3 2 ) K _ B T
- C( 5 2 N ) K _ B T
- D( 5 2 ) K _ B T
Correct answer
D. ( 5 2 ) K _ B T
Step-by-step solution
A diatomic gas molecule at moderate temperatures possesses 5 degrees of freedom: 3 translational and 2 rotational degrees of freedom. According to the law of equipartition of energy, each degree of freedom contributes 1 2 K_ B T to the average energy of the molecule. The total mean energy per molecule E is given by the sum of the energies associated with each degree of freedom: E = f ( 1 2 K_ B T ) Substituting f = 5 for a diatomic gas: E = 5 ( 1 2 K_ B T ) = 5 2 K_ B T Answer: ( 5 2 ) K _ B T