Molar Entropy

Boltzmann Equation for Entropy:

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Karen Ung 2H
Posts: 52
Joined: Fri Sep 29, 2017 7:04 am
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Molar Entropy

Postby Karen Ung 2H » Wed Feb 07, 2018 9:35 pm

The bigger the molecule, the higher the molar entropy. When determining the greater molar entropy, does disorder in the number of different orientations matter more than the size of the molecule?

Sarah Rutzick 1L
Posts: 50
Joined: Tue Oct 10, 2017 7:13 am

Re: Molar Entropy

Postby Sarah Rutzick 1L » Wed Feb 07, 2018 10:49 pm

Larger molecules have more atoms, and therefore have more ways in which they can be arranged. Since entropy measures disorder, larger molecules have larger entropy.

Yashaswi Dis 1K
Posts: 56
Joined: Fri Sep 29, 2017 7:04 am

Re: Molar Entropy

Postby Yashaswi Dis 1K » Wed Feb 07, 2018 10:50 pm

Yes. Technically speaking, the bigger the molecule is implies that the molar entropy will be higher because there are more atoms that can have different positional arrangements (microstates - W), more atoms means more bond vibration energy, and a higher rotational energy etc. all contributing to the molecule having a higher molar entropy. If enough information is given, you can also use the Boltzmann Equation we learned in class S = k*ln(W) to calculate the value of S and rank the molecules based on that.

Note: The k (Boltzmann) constant in the above equation is: 1.381 * 10-23 J/K.

Hope that helps and gives a better conceptual understanding!

Good luck for the midterm!


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