Exothermic reactions






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605136321
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Joined: Wed Sep 18, 2019 12:19 am

Exothermic reactions

Postby 605136321 » Sun Feb 09, 2020 10:57 pm

Why are so many exothermic reactions spontaneous?

Eugene Chung 3F
Posts: 142
Joined: Wed Nov 15, 2017 3:03 am

Re: Exothermic reactions

Postby Eugene Chung 3F » Sun Feb 09, 2020 11:17 pm

All spontaneous processes have an increase in entropy. In other words, heat will always flow from hot to cold and never cold to hot spontaneously. So, S(universe) >0 for spontaneous process (2nd law of thermo.). We also know that delta H is negative for exothermic reactions and that delta G = delta H - T*delta S. So, H will be negative and S will be positive. Thus, G will be negative and spontaneous.

Ruby Richter 2L
Posts: 103
Joined: Thu Jul 25, 2019 12:17 am

Re: Exothermic reactions

Postby Ruby Richter 2L » Mon Feb 10, 2020 10:12 am

What exactly does it mean for a reaction to be spontaneous? I know it involves an increase in entropy but what are other determinants?

rohun2H
Posts: 100
Joined: Wed Sep 18, 2019 12:19 am

Re: Exothermic reactions

Postby rohun2H » Mon Feb 10, 2020 10:21 am

Lavelle briefly mentioned determining spontaneity at the beginning of thermo but I believe he'll be explaining this concept sometime this week.

805422680
Posts: 103
Joined: Sat Sep 14, 2019 12:16 am

Re: Exothermic reactions

Postby 805422680 » Mon Feb 10, 2020 11:06 am

Spontaneous processes have an increase in entropy. Delta H will be negative and S will be positive. Therefore G will be negative and hence the process is spontaneous

Vicki Liu 2L
Posts: 101
Joined: Sat Aug 24, 2019 12:15 am

Re: Exothermic reactions

Postby Vicki Liu 2L » Mon Feb 10, 2020 11:26 am

Conceptually, it makes sense for exothermic reactions to be spontaneous as the release of energy makes the system more stable. Endothermic reactions on the other hand require an input of energy and thus, are not naturally occurring.


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