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)

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.