residual entropy interpretation

Boltzmann Equation for Entropy: $S = k_{B} \ln W$

Payton Kammerer 2B
Posts: 49
Joined: Tue May 01, 2018 3:00 am

residual entropy interpretation

"When the entropy of 1.00 mol CO(s) is actually measured at temperatures close to T = 0 (by using the technique in Topic 4G), the value found is 4.6 J/K. This value—which is called the residual entropy of the sample, the entropy of a sample at T = 0 arising from positional disorder surviving at that temperature—is commonly regarded as close enough to 5.76 J/K to suggest that in the crystal the molecules are indeed arranged nearly randomly. "

I am so confused about this explanation of interpreting entropy at T=0. Is there another way of phrasing this? It just is not clicking. Why can this number tell me about randomness?

Jessica Booth 2F
Posts: 101
Joined: Fri Aug 30, 2019 12:18 am

Re: residual entropy interpretation

At T=0 K, the entropy that a molecule has is just due to the different microstates that the molecule could be in. At t=0 there are no other forms of entropy so you just have to calculate the entropy that arises from the molecule occupying different positions.

Ellen Amico 2L
Posts: 101
Joined: Thu Sep 19, 2019 12:16 am

Re: residual entropy interpretation

When T = 0 K that's the absolute zero for temperature, so the molecules won't have any kinetic energy and therefore no movement, so their entropy is all based on the different positions/microstates the molecules can occupy.

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