AAMC 7 Entropy

[folktale]

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Rxn:
2(N2H4) (l) + N2O4 (l) -> 3N2 (g) + 4 H2O (g)

The entropy change for the reaction is:

C. >0 because the moles of gaseous products > moles of gaseous reactants
D. >0 because water is product of the reaction

I know it was going to be greater than 0, so through POE, I had to choose between these two. C looked nice until I thought to myself that it was a trap since it said "gaseous" reactants even though the reactants were liquid. So I ended up picking D, but the answer was C. C sounded right, until the fact that when I saw "gaseous reactants" made me think twice and ended up picking D. Explain this please? I mean they could have at least said "liquid reactants" instead of "gaseous reactants" to make it sound right. If that was the case, I wouldn't have doubted to pick C.

 

[syoung]

Think you just have to compare the number of moles of product compared to reactants, regardless of the state in the answer choices. Plus, D doesn't make sense through POE as well, so C is your only answer.

 

[folktale]

Think you just have to compare the number of moles of product compared to reactants, regardless of the state in the answer choices. Plus, D doesn't make sense through POE as well, so C is your only answer.

Yeah, I'm pretty sure the moles comparison is the best indicator for the entropy change. It was just the terminology that got me. Is this a possible typo? Because the wrong phase mentioned for the reactants made me think it was a wrong answer that seems right if you don't look closely.

 

[MedPR]

Yeah, I'm pretty sure the moles comparison is the best indicator for the entropy change. It was just the terminology that got me. Is this a possible typo? Because the wrong phase mentioned for the reactants made me think it was a wrong answer that seems right if you don't look closely.

It's not a typo. There are zero gaseous reactants and any positive number is greater than zero.