kinetics and thermodynamics

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Peter Nguyen 2I
Posts: 61
Joined: Fri Sep 28, 2018 12:29 am

kinetics and thermodynamics

Postby Peter Nguyen 2I » Sun Mar 03, 2019 7:30 pm

Which one is prevailant over the other in controlling a reaction? Are there certain conditions where thermodynamics control the reaction?

kateminden
Posts: 63
Joined: Fri Sep 28, 2018 12:24 am

Re: kinetics and thermodynamics

Postby kateminden » Sun Mar 03, 2019 7:39 pm

I was wondering this too! Also can someone please explain why a diamond is kinetically stable with respect to graphite, but thermodynamically unstable? I just can't really wrap my head around the two concepts. Thanks!

Vanadium Wang 4H
Posts: 60
Joined: Fri Sep 28, 2018 12:19 am

Re: kinetics and thermodynamics

Postby Vanadium Wang 4H » Tue Mar 05, 2019 11:25 pm

In principle, every reaction is on the continuum between pure kinetic control and pure thermodynamic control. These terms are with respect to a given temperature and time scale. A process approaches pure kinetic control at low temperature and short reaction time. At the other end of the continuum, thermodynamic control is approached with a sufficiently long time scale and high temperature.

A large activation barrier for conversion exists between diamond and graphite. There is no easy mechanism for this conversion and so transforming diamond into graphite, or vice versa, requires almost as much energy as destroying the entire lattice and rebuilding it. Once diamond is formed, it cannot reconvert back to graphite because the barrier is too high. So diamond is said to be metastable, since it is kinetically stable, not thermodynamically stable.

Hedi Zappacosta 1E
Posts: 66
Joined: Fri Sep 28, 2018 12:27 am

Re: kinetics and thermodynamics

Postby Hedi Zappacosta 1E » Wed Mar 06, 2019 10:35 am

Thermodynamics can never tell us the rate of a reaction. often times we use a combination of thermodynamics and kinetics to fully understand a reaction.

varunhariharan
Posts: 30
Joined: Mon Jan 07, 2019 8:16 am

Re: kinetics and thermodynamics

Postby varunhariharan » Wed Mar 06, 2019 11:15 am

Neither is prevalent in controlling a reaction; they each refer to different concepts. Kinetics has to do with the rates of reactions, while thermodynamics focuses on changes in energy during reactions and spontaneity.


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