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# Enthalpy of solution watch

1. Must the enthalpy of solution be positive or negative for a compound to be soluble?
2. Either.
3. It can be either, since entropy also plays a part in whether or not a reaction [including dissolving] will happen spontaneously.
4. (Original post by oyyoyy)
It can be either, since entropy also plays a part in whether or not a reaction [including dissolving] will happen spontaneously.
(Original post by EierVonSatan)
Either.
I don't fully understand why. I know it refers to the entropy, but I'm really confused.
5. Well you know if a reaction is more disordered, the more likely it will happen (in erase entropy)

I don't think enthalpy of solution has anything to do with entropy though? It's to do with solvation, lattice enthalpy and in some cases the term hydration is thrown in. There is enough energy created from the bond formed between the solution, say from the formation of water molecules bonded to sodium chloride (in there ions, that is) to produce negative and positive solvated ions, if that made any sense, so it shouldn't matter...? But I'm only going with what I've learned on the board I'm with...
6. It is ΔG that is a driving force. ΔG=ΔH-TΔS - so for highly exothermic reactions ΔH is typically decisive, but sometimes even the reaction is endothermic, TΔS is high enough to overcome the enthalpic part and make the reaction spontaneous.

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