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Posted: Sun Mar 01, 2020 8:20 pm
I'm still having difficulty understanding what it means if a reaction is spontaneous. How could a reaction be spontaneous but also never proceed in the forward direction (diamonds to graphite example)?
Posted: Sun Mar 01, 2020 8:27 pm
The reaction of diamonds to graphite does occur, and it is spontaneous. It just occurs at an EXTREMELY slow rate.
Posted: Sun Mar 01, 2020 8:28 pm
This is due to kinetic stability. For diamond to become graphite, there is a large activation energy barrier that needs a lot of energy to overcome and ultimately prevents the conversion to graphite in a forward direction
Posted: Sun Mar 01, 2020 8:32 pm
While a reaction is spontaneous, its activation energy could be so large that it occurs at an incredibly slow rate.
Posted: Sun Mar 01, 2020 8:49 pm
Another way to imagine this is that a reaction such as that actually has two steps. One where the bonds of the reactants are broken, and one where the bonds of the products are formed. To break bonds, you need to put in energy.