Question

calculate the kinetic energy of 2 moles of Argon at 127°C
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Answer 1

Answer:

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Answer 2

Answer:

Imagine a single atom. In a three dimensional space, it can move freely along the X, Y and Z axis. Motion from one point to another is also known as translation. Hence, this movement along the three axes is called translational movement. If you have to specify the location of this atom, then you need three coordinates (x, y, and z).

We can also say that a single atom has 3 Degrees of Freedom. Most monoatomic molecules (i.e. molecules having a single atom like Argon) have 3 translational degrees of freedom, provided their movement is unrestricted.

Law of Equipartition of Energy

(Source: Wikipedia)

Let’s now imagine a diatomic molecule (a molecule having two atoms like O2 or N2). Apart from the three translational degrees of freedom, these molecules can also rotate around the centre of mass. Two such rotations are possible along the axis normal to the axis that joins the two atoms.

This adds two additional degrees of freedom (rotational) to the molecule. In simpler words, to specify the location of the molecule, you would need the X, Y and Z coordinates along with the rotational coordinates of the individual atoms.

It is important to note here that these diatomic molecules are not rigid rotators (where molecules do not vibrate) at all temperatures. Along with the translational and rotational movements, diatomic molecules also oscillate along the interatomic axis like a single dimensional oscillator. This adds a vibrational degree of freedom to such molecules.

Hence, to specify the location of a diatomic molecule, you would finally need the X, Y and Z coordinates along with the rotational and vibrational coordinates. So, in a nutshell, Degrees of Freedom is nothing but the number of ways in which a molecule can move. This forms the basis of the Law of Equipartition of Energy.