Entropy Practice Quiz 2014 #6

[Jordanmjones13]

6. Which of the following statements is correct?
a) C2H5OH (at 298 K) has higher molar entropy than CH4 (g), because C2H5OH 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 (g) has higher molar entropy than C2H5OH because gases have a higher entropy than liquids.
c) 1.0 g of CH4 (g) has the same entropy as 2.0 g of CH4 (g) because entropy is an intensive property (a property that is independent of the amount of substance).
D) A and C are correct.
E) B and C are correct.

The correct answer is B, but I do not understand why this is right and why the other answers are wrong. Could someone please explain. Thanks.

[Chem_Mod]

A) is not correct because C2H5OH is liquid at 298 K (room temperature). This is just ethanol (drinking alcohol)
B) is correct since gas entropy > liquid entropy, same reason why A) is wrong
C) is wrong because entropy is extensive

[Sara Pena 1I]

So regardless of the size of the molecule, a gas will always have higher entropy than a liquid? Will there ever be a case where a liquid will have higher entropy than a gas?

[Cesar Martinez 2A]

So regardless of the size of the molecule, a gas will always have higher entropy than a liquid? Will there ever be a case where a liquid will have higher entropy than a gas?

In general, yes. Gases tend to have higher entropy because entropy is essentially the amount of disorder in a molecule or atom. Molecules in liquids have the ability to move around with respect to each other, but gases can move around the most, which means they have more disorder.
The only way that a liquid can have more entropy than a gas is if there is a much greater amount of liquid than the gas, since entropy is an extensive property. For instance, the total entropy in a 1L container of hydrogen gas is going to be much, much smaller than the entropy in the pacific ocean.