Question:
Consider a gas of triatomic molecules. The molecules are assumed to be triangular and made of massless rigid rods whose vertices are occupied by atoms. The internal energy of a mole of the gas at temperature $T$ is :
Correct Option: 4,
Solution:
(4) Here degree of freedom, $f=3+3=6$ for triatomic nonlinear molecule.
Internal energy of a mole of the gas at temperature $T$,
$U=\frac{f}{2} n R T=\frac{6}{2} R T=3 R T$