question_answer

The degrees of freedom of a molecule of a triatomic gas are :

A)  2               

B)  4

C)  6               

D)  8

Correct Answer: C

Solution :

Key Idea: A triatomic molecule can rotate about any of three coordinate axes. The molecule of a triatomic gas has a tendency of rotating about any of three coordinate axes. So, it has 6 degrees of freedom; 3 translational and 3 rotational. At high enough temperature a triatomic molecule has 2 vibrarional degrees of freedom. But as temperature requirement is not given, so we answer simply by assuming triatomic gas molecule at room temperature. Thus,                 \[f=6\] (3 translational + 3 rotational) at room temperature.