Midterm question 6a

[Ishan Saha 1L]

On this problem on the midterm, both A and B were considered correct answers. For future reference, what answer is correct? Should we think that any gas always has more entropy than any liquid? If not, how do we know if a molecule is complex enough to have more entropy as a liquid than a simple molecule as a gas.

[Chem_Mod]

Hello,

Please include the question that you are asking in regards to.

Thank you.

[Ishan Saha 1L]

Hi,

The question was
"Which of the following statements is correct?"
and both A and B (shown below) were accepted as correct answers on the past midterm. My question is, in the future, which answer is correct? Should we think that any gas always has more entropy than any liquid? If not, how do we know if a molecule is complex enough to have more entropy as a liquid than a simple molecule as a gas?

Options A and B:
A. C₈H₁₈(l) (at 298 K) has higher molar entropy than CH₄(g), because C₈H₁₈ is a larger molecule than CH4, and larger molecules have more chemical bonds and can store energy in more ways than smaller molecules.
B. CH₄ as higher molar entropy than C₈H₁₈ (l) because gases have a higher entropy than liquids.

Hope that clarifies my question, and Thank you!

[Michael Downs 1L]

I think it has something to do with the wording of the answers

[Cristina Sarmiento 1E]

They were both correct because complex molecules have more entropy than less complex molecules and gas has more entropy than liquid.

[Ilan Shavolian 1K]

I believe you can safely assume that the entropy difference from liquid to gas is going to more than the increase in entropy of a more complex molecule.