what does it mean when kinetics rather than thermodynamics is controlling a reaction

[205150314]

What does that mean?

[Ryan Yee 1J]

In the example from Dr. Lavelle's lecture, the conversion of diamond to graphite is thermodynamically stable, however it isn't kinetically stable, so diamond remains as diamond despite the conversion being thermodynamically favored. Because the conversion isnt kinetically stable, the reaction does not proceed forwards.

[kevinolvera1j]

Thermodynamics typically deals with state functions whereas kinetics deals with different pathways that control the speed of the reaction. This especially comes into play when dealing with activation energies

[Madeline Ogden 3B]

Thermodynamics deals with how favorable a reaction is, whereas kinetics deals with the speed/rate at which the reaction will take place. In reference to the diamond and graphite example that a student mentioned earlier, the reason that people are willing to spend so much on diamond jewelry is that although the transition from diamond to graphite is thermodynamically favored, it is not kinetically favored. Therefore, the reaction of diamond turning into graphite is very very slow and will never occur within the timeframe of one (or more) human lifetimes.

[Joshua Eidam 2A]

The diamond to graphite example is perfect for representing what "controlling a reaction" really means. Although the thermodynamic aspect of the reaction would suggest that the reaction of diamond to graphite should take place rather easily, there is a huge energy barrier in the way due to diamond being incredibly kinetically stable. Because of this, the reaction is kinetically controlled and will take a very long time to occur.

[Alexis Sanft 1E]

Thermodynamics deals with how favorable a reaction is, whereas kinetics deals with the speed/rate at which the reaction will take place. In reference to the diamond and graphite example that a student mentioned earlier, the reason that people are willing to spend so much on diamond jewelry is that although the transition from diamond to graphite is thermodynamically favored, it is not kinetically favored. Therefore, the reaction of diamond turning into graphite is very very slow and will never occur within the timeframe of one (or more) human lifetimes.

If a reaction is favorable in thermodynamics does it mean it is spontaneous and unstable?

[Gillian Gabrielsen2F]

It means even though the reaction is thermodynamically stable, ΔG<0, the activation energy is extremely high, leading to the reaction not occurring.

[Immi Lee - 1D]

Hi! This a follow-up question, but are there any other examples besides diamond and graphite that might appear/be asked on the final?

[Felicia Wei 1B]

The occurrence of a reaction may depend more on whether it is more kinetically favored rather than thermodynamically. Usually, thermodynamics states that a reactant becoming a more stable product will always be more favorable however the reaction may not occur if it is not kinetically favorable thus it will occur but at an extremely slow speed.