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Topic: Making Iron Oxide  (Read 17119 times)

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Offline jdurg

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Re:Making Iron Oxide
« Reply #15 on: July 16, 2004, 04:59:31 PM »
good point, but once you've got the bond, there should be enough energy holding it together to tell off thermodynamics as opposed to the bond with say.. triiodide stuff. obviously it can't be thermodynamically sound for iron and oxygen to fall apart, because iron will oxidize just by sitting in a humid environment. why is that then? I mean, I understand the point about entropy, but not just iron can oxidize and stay that way. aluminum oxide for instance. so why DO things oxidize if it goes against the idea of entropy?

Entropy isn't the only thing that determines if a reaction will happen.  Overall, you have to look at the Gibbs Free Energy for a reaction.  A negative ?G will mean that a reaction is favored to happen, and a positive one indicates that it isn't likely/won't happen.

?G = ?H -T?S

So a reaction with a highly negative ?H and a highly positive ?S is favored to go ahead.  So in a reaction where the entropy decreases, if the enthalpy is highly negative, then it will be favored to proceed.  
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