Re: Thermoneutral Reactions?
From: Bob (bbx107_at_excite.com)
Date: 01/30/05
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Date: Sun, 30 Jan 2005 10:02:49 -0800
On 30 Jan 2005 04:50:17 -0800, farooq_w@hotmail.com wrote:
>Can somebody give a common example of a thermoneutral chemical reaction
>(no heat evolved or absorbed)? I thought that every reaction was either
>endothermic or exothermic but never heard of a thermoneutral reaction
>until browsing a book on chemical kinetics where they just mentioned in
>a single line about these reactions. Many other kinetics texts such as
>Laidler, Logan do not mention this term at all. Just thinking can
>isotope-exchange reactions can they be classified as thermoneutral
>reactions?
Misc points...
As others have noted, since dH can have any value, there is nothing
wrong with it being zero, or as close to zero as you want.
Of course, it is dG that normally determines whether a reaction
occurs. But remember the distinction between dG and dGo. At
equilibrium, dG is zero, but the reaction is proceeding, in both
directions at equal rate.
I would think that mixing reactions between very similar, minimally
interacting, substances would have dH near zero.
Somewhere very recently, I just noted a paper in which they claim that
a certain class of explosives (peroxides) may decompose with dH about
zero -- with the entire energy release being pV.
bob
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