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Posted: Fri Feb 08, 2019 12:44 am
In lecture, Lavelle said that if the change in internal energy or the change in enthalpy were negative, we could ask if the reaction could be predicted to occur. He also mentioned that we could question if the reaction would be spontaneous and that it was likely to be. How would we know that/figure that out?
Posted: Fri Feb 08, 2019 12:55 am
To address the spontaneity, think of the example he mentioned about the boulder on the mountain; it will roll down the side by itself (spontaneously), but it won't roll up the mountain itself. Energy through the form of work is needed to push that boulder up the mountain. If something can occur by itself without "outside intervention" it's considered spontaneous.
Posted: Fri Feb 08, 2019 9:55 am
To add a chemistry example for spontaneity, imagine having one of those pumps Lavelle draws out. If the pressure inside the system is different from the pressure outside the system, the pump will move on its own to try to make the outside pressure equal to the system's pressure.