Stupid Gchem question..

[nickatina]

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i have a question about topscore question 62 on the second test of natural sciences.

Which of the following reactions has a negative change in entropy?

C) 2 NO (g) + O2 (g) --> NO2 (g)
D)H2O (g) --> H2O (l)

ok so the answer is D which makes sense, but why cant C also be an answer. we are going from 3 moles of gas to 1 mole of gas, so the moles of gas go down.
after thinking about it some more does C not work because if we reduce the moles of gas those molecules will have more space to move around and therefore increase in entropy?
I think ive been studying so long that the easy questions are making me second guess the answer my gut says is correct

 

[ernest1284]

hey, i think they are both a decrease in entropy, but since the h20 changes phase from a gas to a liquid......... and since (solid to liquid to gas) entropy increases drastically the bigger change would be the phase change of h20

 

[BlueEyes'06]

i have a question about topscore question 62 on the second test of natural sciences.

Which of the following reactions has a negative change in entropy?

C) 2 NO (g) + O2 (g) --> NO2 (g)
D)H2O (g) --> H2O (l)

ok so the answer is D which makes sense, but why cant C also be an answer. we are going from 3 moles of gas to 1 mole of gas, so the moles of gas go down.
after thinking about it some more does C not work because if we reduce the moles of gas those molecules will have more space to move around and therefore increase in entropy?
I think ive been studying so long that the easy questions are making me second guess the answer my gut says is correct[/QUOTE

entropy increases from gas>liquid>solid, where gas has the highest entropy, D would be correct, since ur going from gas to a liquid decrease in entropy
C could not be because entropy stays the same, product u have gas and reactant u have gas, i think what ur talking about 3 moles and 1 moles is when u're dealing with Le'Chatelier principle...............anyways that's the only reason I can think of..........good luck studying

 

[BlueEyes'06]

i have a question about topscore question 62 on the second test of natural sciences.

Which of the following reactions has a negative change in entropy?

C) 2 NO (g) + O2 (g) --> NO2 (g)
D)H2O (g) --> H2O (l)

ok so the answer is D which makes sense, but why cant C also be an answer. we are going from 3 moles of gas to 1 mole of gas, so the moles of gas go down.
after thinking about it some more does C not work because if we reduce the moles of gas those molecules will have more space to move around and therefore increase in entropy?
I think ive been studying so long that the easy questions are making me second guess the answer my gut says is correct

entropy increases from gas>liquid>solid, where gas has the highest entropy, D would be correct, since ur going from gas to a liquid decrease in entropy
C could not be because entropy stays the same, product u have gas and reactant u have gas, i think what ur talking about 3 moles and 1 moles is when u're dealing with Le'Chatelier principle...............anyways that's the only reason I can think of..........good luck studying

 

[allstardentist]

entropy increases from gas>liquid>solid, where gas has the highest entropy, D would be correct, since ur going from gas to a liquid decrease in entropy
C could not be because entropy stays the same, product u have gas and reactant u have gas, i think what ur talking about 3 moles and 1 moles is when u're dealing with Le'Chatelier principle...............anyways that's the only reason I can think of..........good luck studying

in both cases, the entropy decreases (negative delta s) but i think the entropy drop is greater in phase change going from solid -> liq -> gas (in this case,solid to liquid). thats my guess. not 100% sure though.