Kinetic Theory

JEE Main level, single correct, medium

80 of 168

Question 80 of 168

Match List I with List II: List I List II (A) 33 Translational degrees of freedom (I) Monoatomic gases (B) 33 Translational, 22 rotational degrees of freedoms (II) Polyatomic gases (C) 33 Translational, 22 rotational and 11 vibrational degrees of freedom (III) Rigid diatomic gases (D) 33 Translational, 33 rotational and more than one vibrational degrees of freedom (IV) Nonrigid diatomic gases Choose the correct answer from the options given below:

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Answer: (A) (A)−(I),(B)−(III),(C)−(IV),(D)−(II)\left(A\right)-\left(I\right),\left(B\right)-\left(III\right),\left(C\right)-\left(IV\right),\left(D\right)-\left(II\right)

The formula for degree of freedom is given by
f=3N−kf=3N-k
where
NN is the number of particles, kk is the individual relationship in the system.
For a monoatomic gas particle,
N=1,k=0N=1,k=0. So, f=3f=3
Hence, monoatomic gas has
33 translational degree of freedom.
For a rigid diatomic gas molecule, there are
55 degrees of freedom, 33 translational and 22 rotational. A diatomic gas can have two extra degrees of freedom due to rotation along two independent axes.
A non rigid diatomic molecule has one extra degree of freedom than a rigid one. This is the vibrational degree of freedom. Hence, it has
66 degrees of freedom.
So, a non rigid diatomic gas has
33 translational, 22 rotational and 11 vibrational degrees of freedom.
A polyatomic gas has more than two atoms per molecule. Hence, the total number of degrees of freedom is
33 translational, 33 rotational and more than one vibrational degree of freedom.

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