spontaneous rxn

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guys i always get this wrong: can you clarify this for me that why C is the wrong ans?
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Well here the answer is E...hmm the delta G of the system is always negative when enthalpy (delta H) is negative and the entroy (delta S) is positive. I believe this is talking about the delta G of universe! But if I'm right this question needs to be a bit more specific
 
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i think it has to ddo with the keyword they put in "always" b/c technically you don't always need a negative enthalpy and positive entropy for a spontaneous rxn. for example u can have a positive enthalpy with a positive entropy at very high temperatures, which would give u a negative delta G (spontaneous) sooo on that note, E is a better choice b/c E can never be disproved no matter what what sign enthalpy and entropy have.

hope that helps!
 
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Well, for a spontaneous rxn there has to be a decrease in Gibbs free energy.
Though a negative change in enthalpy and a positive change in entropy would result in a spontaneous rxn, a spontaneous rxn doesn't necessarily need "those" changes/ conditions to occur. However!! if there is a negative change in Gibbs free energy there will be a spontaneous rxn and a spontaneous rxn needs Gibbs free energy to occur.

Its a matter of elimination. E and C are correct but E would Always occur for a spontaneous rxn, whereas a spontaneous rxn doesn't necessarily need the conditions of C to occur.
 
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The answer to this question depends on the magnitude of the entropy, enthalpy, and T. E is always correct, and is the definition of whether or not a reaction will be spontaneous. Choice C does make sense. If H is negative, and T is always positive, a positive S value will cause G to be negative.
 
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Choice C tells you the steps of how you get a spontaneous reaction, but E states the overall result
 
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flycd05. great explanation. thanks. can i have your email address so i can be in touch with you if i come up with problems relating DAT?
thanks.
 
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When talking about spontaneous reactions, you always want to think of gibbs free energy, regardless of enthalpy and entropy.. Delta G is what makes a reaction spontaneous or nonspontaneous.

I think you are overthinking the question too much. Its a relatively simple question which is very common on the DAT. They make you over think things and second guess yourself. Don't fall into that trap!

Hope this helps!


Good luck!!
 
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