Question

mention the degrees of freedom for a triatomic gas molecule

Answer 1

A triatomic molecule has 9 degrees of freedom, in general. There are 3 translational modes, 3 rotational and 3 vibrational. The "6 degrees of freedom" triatomic molecule neglects the vibration modes, which usually are not active at room temperature. Same as for diatomic gas (6 degrees of freedom) the vibration mode does not contribute to heat capacity at room temperature so the gas has only 5 active modes.

Answer 2

In triatomic gas there are in total 9 degree of freedom.

Triatomic gas is composed of 3 non linear molecules so will have 9 degree of freedom that is 3 transitional degree of freedom, 3 rotational and 3 vibrational degree of freedom.

Degree of freedom are the different ways in which molecule can move in 3D space. A tiatomic has 9 different ways of movement they are:-

(1) Transitional degree of freedom is the way in which molecule can move in state line only and there are 3 transitional degree of freedom in triatomic.

(2) Rotational degree of freedom is the way it which molecules are in circular or rotatory motion and there are also 3 in triatomic gas.

(3) Vibrational degree of freedom is shown by molecule in excited state when molecules vibrate in their place only. The to and fro motion of particle about fixed position is vibrational motion and are 3 in non linear triatomic gases.

So total there are 9 degree of freedom for triatomic gases.