destroyer question #91

[Jordwin]

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This seems like a seemingly easy enough question.

The question asks "Which statement(s) is false?
A) All spontaneous reactions result in an increase in enthalpy of the universe
B) All spontaneous reactions result in an increase in entropy of the universe
(C-D- not issues)
E) Two of the above

I chose E because I thought that entropy could be negative in a spontaneous reaction if enthapy was a large negative number. Apparently I was wrong, though. The answer is A.

 

[yko0584]

This seems like a seemingly easy enough question.

The question asks "Which statement(s) is false?
A) All spontaneous reactions result in an increase in enthalpy of the universe
B) All spontaneous reactions result in an increase in entropy of the universe
(C-D- not issues)
E) Two of the above

I chose E because I thought that entropy could be negative in a spontaneous reaction if enthapy was a large negative number. Apparently I was wrong, though. The answer is A.

the way i think of it is spontaneous reactions are exothermic, which means there is a release of heat as stuff are broken down. Entropy should increase in spontaneous reactions. Im not really sure about enthalpy I think energy needed for the reaction should be small or negative for spontaneous reactions.

 

[hope_to_match]

I would choose B as the correct statement.This is the 2nd law of thermodynamics. There is no law that mentions enthalpy of the Universe increasing...therefore A is the correct answer in this question, since you are being asked about which statement is false. You were right, entropy can be negative in spontaneous reactions, given that enthalpy is negative at low temperatures, but the word 'universe' is the key here and 2nd law o thermodynamics is implied by B, therefore A is not a correct statement.

 

[mostprecious]

Eugeniager is right. If both H (enthalpy) and S (entropy) are negative, then the reaction is spontaneous only in low temperatures, not always. The statement is saying "all spontaneous reactions result in increase in enthalpy of the universe." That's why it's false. If it said "in low temperature, a spontaneous reactions has negative enthalpy," then it's a true statement.

If a reaction has +S and -H, then it's spontaneous in all temperatures.
If -S and +H, then it's non-spontaneous in all temperatures.
If -S and -H, then spontaneous in low temperatures.
If +S and +H, then spontaneous in high temperatures.

 

[Jordwin]

Yeah, I knew the Gibbs equation and what makes it negative. I was mainly wondering why it said that all spontaneous reactions lead to an increase in entropy.
I was wondering because a high negative H could bring about a negative g without a positive s (low temp).

 

[hope_to_match]

Yeah, I knew the Gibbs equation and what makes it negative. I was mainly wondering why it said that all spontaneous reactions lead to an increase in entropy.
I was wondering because a high negative H could bring about a negative g without a positive s (low temp).

you are overthinking this. the key is the word 'universe'. even though some rxns might have negative S (and therefore entropy would be decreasing) overall the rxns will still result in an increase in entropy of the the universe . this is the second law of thermodynamics. this is sort of like a whole is greater than the sum of its parts kind of thing

 

[Jordwin]

Universe, gotcha! Thanks for the clarification.

 

[hope_to_match]

Universe, gotcha! Thanks for the clarification.

you are welcome! 🙂

 

[gn4]

seriously Eugeniager, reading your posts everywhere tells me that you are ready for this test. When is the big day?

 

[hope_to_match]

seriously Eugeniager, reading your posts everywhere tells me that you are ready for this test. When is the big day?

i dont feel ready..i am planning for end of August. Didnt register yet 🙂

I am not ready for bio yet 🙂

 

[gn4]

i dont feel ready..i am planning for end of August. Didnt register yet 🙂

I am not ready for bio yet 🙂

I don't think you will ever really feel ready. I never felt ready either. Good luck nonetheless, I feel like you will destroy it. Good luck.

 

[hope_to_match]

I don't think you will ever really feel ready. I never felt ready either. Good luck nonetheless, I feel like you will destroy it. Good luck.

thank you! I hope so too. I really need to do well on this test (who doesnt? 😀
I will let you guys know when I take it/register for it :O)

 

[Jordwin]

thank you! I hope so too. I really need to do well on this test (who doesnt? 😀
I will let you guys know when I take it/register for it :O)

I'm just registering for mine today. Looking like September 3rd. I feel like we are in the same boat here, prolonging the inevitable! Ha