AirCowPeaCock
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Sulfuric acid and water, why is the reaction exothermic?
Why is the reaction of H2SO4 + H2O exothermic? Hydrogen has a higher ionization energy than oxygens electron affinity..?
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Adas
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Because the H2SO4 hydrolyzes: H2SO4 + H2O ----> HSO4- + H3O+
Rest In Pieces!
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kavu
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This is basic college level chemistry. In order to calculate reaction enthalpy (ie. heat of reaction) add up the formation enthalpies of the products
multiplied by their stoichiometric coefficients and subtract from this formation enthalpies of the reactants multiplied as before. This method is
based on the assumption that we can imagine breaking all the bonds in the reactants, which requires some energy. After that we form bonds present in
the products from the atoms and gain some energy. Energy difference of these two tells us if the reaction is exothermic or endothermic. In the case of
dissolving H2SO4 in water the reaction is exotermic, meaning that products are lower in energy than the starting materials.
[Edited on 23-1-2012 by kavu]
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AirCowPeaCock
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Huh...the section on enthalpy in my textbook is not even a page long, and barely brushes on the subject. Maybe that's why it was 8$ at half price
books! 
[Edited on 1-23-2012 by AirCowPeaCock]
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zoombafu
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Quote: Originally posted by AirCowPeaCock  | Huh...the section on enthalpy in my textbook is not even a page long, and barely brushes on the subject. Maybe that's why it was 8$ at half price
books!
[Edited on 1-23-2012 by AirCowPeaCock] |
I get almost all of my text books from half priced books!
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entropy51
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7.4 messages per day and not one of them is worth reading.
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AirCowPeaCock
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Harsh! Haha
Half price should really be called 1/10th price books! Im sure this text new was a lot more than 16$, in fact it was probably about 160$! My calc
text is from there too..12$(:
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GreenD
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Exothermic; Energy is given off. That energy comes from somewhere. It would mean, then, that the solution of sulfuric acid and water is actually more
"stable" (lower in energy) than the two seperate compounds. Therefore the bond O-H bond in H3O+ is lower in energy than the H-O in H2SO4.
H2SO4 + H2O > HSO4- + H3O+
Good question.
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AirCowPeaCock
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Thank you! So does that mean the O-H bond in H2SO4 is "weaker" than the H3O bond?
[Edited on 1-26-2012 by AirCowPeaCock]
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turd
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College? High school!
http://www.science.uwaterloo.ca/~cchieh/cact/applychem/hydra...
Start reading and stop spamming the forums.
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AirCowPeaCock
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highschool? They're still teaching what oxidation <b>is</b> in honors chem! They really don't teach chemistry in this state...
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GreenD
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Kind of, yes. Really all you can really say without much detail is the H3O+/HSO4- is lower in energy than H2O/H2SO4.
This is enthalpy. I don't think it is the case, but in some solutions, entropy plays a big roll in exothermic/endothermic. That is the complexation
(or the order) of the molecules in solution dramatically changes the chaotic nature (or vice-versa).
I really enjoyed enthalpy and entropy in chemistry. They connect the small molecules to the "BIG" picture... You can know if any reaction will happen
if you know about the entropy and enthalpy.
The philosophy of entropy is interesting
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AirCowPeaCock
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Then I'll certainly put much more effort into learning about them, my chem text is very basic--its kind of an introduction to general, organic, and
biochem.
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