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Posted: Sat Jan 27, 2018 8:33 pm
Hi all! I am still confused as to what the actual definition of spontaneity is, if we do not use the word "disorder." I know Dr. Lavelle went over it in class, but a little clarification would be much appreciated!
Posted: Sat Jan 27, 2018 9:55 pm
Spontaneous reactions are reactions that tend to occur without external influence as in by itself. Dr. Lavelle avoids saying disorder for entropy.
Posted: Sat Jan 27, 2018 10:20 pm
A spontaneous reaction is a reaction that occurs without help. The example he used in class really helps; the one with the closed round flask.
If that example doesn't help too much you can also think of it like this. If some sort of gas was held in a closed flask by some sort of cork and that cork was removed, the gas in the flask would come out by itself. That's a spontaneous reaction.
We don't normally see the gas going back inside the flask by itself. It wouldn't just return to the flask so it could be capped by the cork again. If we wanted that gas back in the flask, we'd have to manually do it. This type of reaction is non spontaneous.
Posted: Sun Jan 28, 2018 5:04 pm
Spontaneous reactions do not require energy input to occur, and that's why they will happen on their own. Vice versa for non-spontaneous reactions.
Posted: Sun Jan 28, 2018 5:37 pm
Also spontaneous reactions with gas can't occur while going to a smaller volume because that would require energy but larger volume wouldn't need anything to happen
Posted: Sun Jan 28, 2018 6:02 pm
You can think of a spontaneous reaction as something that occurs on its own, without an external nudge, i.e. an input of energy. A reaction that requires an input of energy does not occur on its own, and is therefore not "spontaneous."