dissolution -> why would it be spontaneous?

[SuperSaiyan3]

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Alright, so from my knowledge of spontaneity, it is something that is FAVOURED.

and from my knowledge from bonds:

- energy is given off when bonds are made
- energy is needed to break the boonds

So in a dissolution reaction, WHY oh WHY would this be spontaneous? I am of course, referring to AAMC4 question #21.

If you're breaking the bonds in a crystal lattice structure, wouldn't you need to put IN the energy? Thus being a nonspontaneous reaction?

I've got clouds in my head!!

 

[G1SG2]

Alright, so from my knowledge of spontaneity, it is something that is FAVOURED.

and from my knowledge from bonds:

- energy is given off when bonds are made
- energy is needed to break the boonds

So in a dissolution reaction, WHY oh WHY would this be spontaneous? I am of course, referring to AAMC4 question #21.

If you're breaking the bonds in a crystal lattice structure, wouldn't you need to put IN the energy? Thus being a nonspontaneous reaction?

I've got clouds in my head!!

Yes, you put in energy to break the bonds of the crystal lattice structure. However, you also have take into consideration the bonds formed between the solvent and the dissociated solute. If they are stronger than the bonds formed in the crystal lattice, then the overall delta H is negative, and assuming entropy is positive, delta G would be negative, making it a spontaneous process.

 

[amine2086]

Alright, so from my knowledge of spontaneity, it is something that is FAVOURED.

and from my knowledge from bonds:

- energy is given off when bonds are made
- energy is needed to break the boonds

So in a dissolution reaction, WHY oh WHY would this be spontaneous? I am of course, referring to AAMC4 question #21.

If you're breaking the bonds in a crystal lattice structure, wouldn't you need to put IN the energy? Thus being a nonspontaneous reaction?

I've got clouds in my head!!

Not necessarily. The relationship between a spontaneous process and bond breaking/forming is not necessarily a linear one. Remember, whether or not a process is spontaneous is determined by Gibbs free energy. ΔG = ΔH - TΔS. If ΔG is negative, the process is spontaneous. As you can see from the formula, when ΔS is positive and ΔH is negative, a process is spontaneous. When ΔS is positive and ΔH is positive, a process is spontaneous at high temperatures, where exothermicity plays a small role in the balance. For example, decay of diamonds into graphite is a spontaneous process, but this decay is extremely slow and takes millions of years. The rate of a reaction is independent of its spontaneity, and instead depends on the chemical kinetics of the reaction.

On the side not, please post the AAMC exam related question in the appropriate forum.