Question

Translational kinetic energy of hydrogen molecules
at room temperature is 30 J. Their rotational kinetic
[NCERT Pg. 334]
energy is
(1) 30 J
(2) 20 J
(3) 10 J
(4) 48 J​

Answer 1

Given:

Translational kinetic energy of hydrogen molecules at room temperature= 30 J

To find:

The rotational kinetic energy.

Solution:

The translational kinetic energy if a diatomic molecule in each axis is 1/2kT, so for three axes the total translational kinetic energy is 3/2 kT.

The rotational kinetic energy for each axis axis of rotation is 1/2 kT, so for two axes it will be kT.

Therefore the translational kinetic energy is 3/2 times of rotational energy.

So rotational kinetic energy will be 2/3 times if translational kinetic energy = 2/3 *30 = 20 J.

The rotational kinetic energy is 20 J.

Answer 2

20

Explanation:

Translational kinetic energy of hydrogen molecules

[NCERT Pg. 334]

at room temperature is 30 J. Their rotational kinetic

energy is