Question

The I2 molecule has a vibrational frequency of 6.44 THz. What will be the temperature condition in which the constant volume heat capacity will mostly manifest its classic character?

Answer 1

The Debye temperature indicates the approximate temperature limit below which quantum effects may be observed. So for classic character T >

Debye temperature is given by θ_D = hf/k

where k is Boltzmann’s constant(1.38 x 10 ^-23 J/K) , h is Planck’s constant(6.6 ×10⁻³⁴ J⋅s), and f is the maximum frequency of the vibrations(6.44 x 10¹² Hz)

Hence, T > (6.6 ×10⁻³⁴)x(6.44 x 10¹² ) /  1.38 x 10 ^-23

T > 308 K