HW 9.71

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Jay the Nursing Major 3C
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HW 9.71

Postby Jay the Nursing Major 3C » Wed Jan 20, 2016 7:57 pm

9.71 (a) Which substance would you expect to have the highest molar entropy in the liquid phase, benzene, methanol (CH3OH), or 1-propanol (CH3CH2CH2OH)? (b) Would your answer be different if these substances were in the gas phase?

I don't understand why Benzene has higher molar entropy. Since it is in a ring-like structure, shouldn't it have less disorder and thus entropy?

Ronald Yang 2F
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Re: HW 9.71

Postby Ronald Yang 2F » Wed Jan 20, 2016 11:23 pm

I think it's because, the more complex a molecule is, the higher its molar entropy is. Since the molar mass of benzene is higher than the molar masses of each of the rest of the molecules, it holds the most complexity, and thus, the highest molar entropy. You can also think about it in terms of vibrations. The more of something per mole, the more vibrations within the molecule, and so, the more disorder/entropy within that molecule.
Last edited by Ronald Yang 2F on Tue Jan 26, 2016 5:41 pm, edited 1 time in total.

Chem_Mod
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Re: HW 9.71

Postby Chem_Mod » Wed Jan 20, 2016 11:45 pm

The solution manual states that 1-propanol has the highest entropy. It uses benzene's rigidity as a reason for it having LOWER entropy.


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