- #1

Rap

- 827

- 10

Looking at the Sackur-Tetrode equation for the entropy of a mono-atomic ideal gas:

[tex]S=kN\left[\log\left(\frac{V (2\pi m k T)^{3/2}}{N h^3}\right)+\frac{5}{2}\right][/tex]

S is entropy, V is volume, N is number of particles, T is temperature, m is mass of a particle, k is Boltzmann's constant and h is Planck's constant.

What is the point of Planck's constant h? Why couldn't it be just any constant with the same units as h? I mean, you cannot measure absolute entropy, only differences in entropy, and when you do that, the value of h does not matter.

[tex]S=kN\left[\log\left(\frac{V (2\pi m k T)^{3/2}}{N h^3}\right)+\frac{5}{2}\right][/tex]

S is entropy, V is volume, N is number of particles, T is temperature, m is mass of a particle, k is Boltzmann's constant and h is Planck's constant.

What is the point of Planck's constant h? Why couldn't it be just any constant with the same units as h? I mean, you cannot measure absolute entropy, only differences in entropy, and when you do that, the value of h does not matter.

Last edited: