Question

State the law of equipartition of energy. Obtain an expression for the energy per molecule and energy per mole of a rigid diatomic gas

Answer 1

The law of equiparition of energy states that their is equal distribution of energy in every degree of freedom of a gaseous particle and the energy of a gaseous particle per degree of freedom is equal to 0.5KT (where T is the temperature and K is the Boltzman's constant).

• For a rigid diatomic gas molecule there exists three translational degrees of freedoms and two rotational degrees of freedoms.Total number of degrees of freedom is equal to 5.
• So, the energy per molecule = 5×(0.5KT) = 2.5KT
• Energy per mole can be obtained by multiplying the energy per molecule with the Avogadro's number(NA).
• Hence, Energy per mole = 2.5KT×NA = 2.5RT