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 co-ordinate axes. The molecule of a triatomic gas has a tendency of rotating about any of three co-ordinate axes. So, it has 6 degrees of freedom, 3 translational and 3 rotational. At high enough temperature, a triatomic molecule has 2 vibrational 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.