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Positional/Residual Entropy

Posted: Sun Jan 22, 2017 10:53 pm
by julia lai 3A
What exactly is positional and residual entropy, and how is it different from thermal entropy?

Re: Positional/Residual Entropy

Posted: Mon Jan 30, 2017 10:01 pm
by Chem_Mod
Hello Julia!

So we know that entropy is associated with the number of allowed states we have. The more states (W) the larger the entropy. Imagine two CN molecules next to each other. Without any thermal energy, we can have different locations:
For example we can have an arrangement like so: CN CN (with the nitrogen next to the carbon)
We can also have: CN NC (with the nitrogen atoms next to each other)
Another orientation is: NC CN (with the carbon atoms next to each other)

Because there are these different orientations, there is some inherent entropy in a CN molecule that we call positional entropy.