Question

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

• A. 2
• B. 4
• C. 6
• D. 8

Answer 1

Answer: (C)

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 $2$ 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.