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kinetics and thermodynamics

Posted: Sun Mar 03, 2019 7:30 pm
by Peter Nguyen 2I
Which one is prevailant over the other in controlling a reaction? Are there certain conditions where thermodynamics control the reaction?

Re: kinetics and thermodynamics

Posted: Sun Mar 03, 2019 7:39 pm
by kateminden
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!

Re: kinetics and thermodynamics

Posted: Tue Mar 05, 2019 11:25 pm
by Vanadium Wang 4H
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.

Re: kinetics and thermodynamics

Posted: Wed Mar 06, 2019 10:35 am
by Hedi Zappacosta 1E
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.

Re: kinetics and thermodynamics

Posted: Wed Mar 06, 2019 11:15 am
by varunhariharan
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.